Interface Engineering of Hierarchically Confined Pt-MnO 2 /m-Al 2 O 3 Catalysts and Their Performance and Mechanism in Low-Temperature Methane Catalytic Combustion

Interface Engineering of Hierarchically Confined Pt-MnO 2 /m-Al 2 O 3 Catalysts and Their Performance and Mechanism in Low-Temperature Methane Catalytic Combustion | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Interface Engineering of Hierarchically Confined Pt-MnO 2 /m-Al 2 O 3 Catalysts and Their Performance and Mechanism in Low-Temperature Methane Catalytic Combustion Zeng Xiaoyi, Zhang Ruikun, Xiang Xianbing This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6367896/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract In this study, hierarchically confined Pt-MnO 2 /m- Al 2 O 3 catalysts were synthesized via a precipitation method using MnO 2 - Al 2 O 3 as promoters, and their methane catalytic combustion performance and structure-activity relationships were systematically investigated. The results demonstrate that the 0.5 wt% Pt-loaded Pt-MnO 2 /m- Al 2 O 3 catalyst achieved 90% methane conversion at 228 ℃ (T 90 ). The enhanced performance is attributed to three synergistic mechanisms: (1) Pt doping induced lattice contraction in MnO 2 (XRD revealed a 0.03 Å reduction in the (001) interplanar spacing), which facilitated the formation of 3+ -oxygen vacancy pairs (XPS indicated a Mn 3+ - content of 79.87%); (2) The PtO-MnPt 3 O 6 interfacial structure (HAADF-STEM confirmed lattice spacings of 0.23/0.21 nm) accelerated oxygen species cycling, with lattice oxygen desorption capacity (O 2 -TPD) increasing by 38% compared to undoped samples; (3) The mesoporous m-Al 2 O 3 carrier provided effective confinement, achieving a high specific surface area (28.1 m 2 /g) and sub-nanometer Pt dispersion (particle size < 2 nm). Under conditions of 1000 ppm CH 4 and a space velocity of 30,000 h –1 , the catalyst maintained a methane conversion rate of 98.2 ± 0.5% during continuous operation for 30 hours. Post-cycling characterization revealed stable crystalline structure (XRD full width at half maximum of 0.35°±0.02°) and grain size (12.3 ± 0.5 nm), confirming its robustness for industrial applications. This study provides theoretical and experimental foundations for the rational design of highly efficient catalysts for low-concentration methane elimination. Hierarchical confinement Pt-MnO2 interface Oxygen vacancy Methane catalytic combustion Stability Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 Figure 11 Figure 12 1 Introduction Methane catalytic combustion has emerged as an efficient and environmentally benign strategy for eliminating low-concentration methane (typically < 10%), which is widely emitted from natural gas extraction, coal mine ventilation, landfills, and biomass fermentation. This technology holds significant potential for reducing greenhouse gas emissions and enhancing energy utilization efficiency, aligning with global sustainability goals [ 1 ] . Despite its promise, the practical implementation of methane combustion faces challenges due to the low reactivity of methane molecules under mild conditions. Conventional noble metal catalysts, particularly platinum (Pt) supported on porous molecular sieves, exhibit superior activity and selectivity in methane combustion. However, their industrial application is hindered by high costs and rapid deactivation under harsh operational environments. For instance, Pt catalysts suffer from sintering and poisoning under high-temperature or humid conditions, leading to significant performance degradation [ 2 , 3 ] . To address these limitations, advanced structural engineering approaches have been explored. Lee et al. [ 4 ] developed a confined Pt catalyst using 2D layers, demonstrating enhanced resistance to sintering and moisture, albeit at the expense of catalytic activity. Lou et al. [ 5 ] optimized the shell thickness of Pt@MnO 2 core-shell catalysts, achieving improved thermal stability but compromised water resistance. Notably, Pi et al. [ 6 ] reported that SiO 2 or MnO 2 coatings on Pt catalysts significantly enhanced hydrothermal stability while mitigating metal sintering, offering new insights into multifunctional catalyst design. Building upon these advancements, this study proposes a hierarchically confined Pt-based catalyst tailored for low-concentration methane combustion. By integrating MnO 2 and Al 2 O 3 as dual-functional promoters, the catalyst aims to balance high activity with long-term stability. The introduction of MnO 2 facilitates lattice oxygen modulation and oxygen vacancy generation, while the mesoporous Al 2 O 3 framework ensures Pt dispersion at the sub-nanometer scale. Additionally, synergistic interactions at the PtO-MnPt 3 O 6 interface enhance oxygen species mobility, as evidenced by oxygen temperature-programmed desorption (O 2 -TPD) and X-ray photoelectron spectroscopy (XPS) analyses. This design not only optimizes the electronic structure of active sites but also strengthens metal-support interactions, thereby extending catalyst lifespan under cyclic operational conditions [ 7 , 8 ] . Furthermore, the engineered oxygen storage-release capacity of the promoters promotes Pt reoxidation, effectively suppressing catalyst deactivation [ 2 , 9 ] . The systematic investigation of structure-activity relationships in this work provides a foundational framework for developing robust methane combustion catalysts with industrial viability. 2 Experimental Section 2.1 Catalyst Preparation A dual-active-site Pt-based catalyst (M 1 -MnO 2 /m-Al 2 O 3 ) was synthesized via a precipitation method using Al 2 O 3 as the primary support. (1) Synthesis of Al 2 O 3 Support 5.0 g of Al 2 (SO 4 ) 3 was dissolved in 100 mL of deionized water under magnetic stirring for 0.5 h. The solution was transferred into a 500 mL Teflon-lined autoclave and subjected to hydrothermal treatment at 140 ℃ for 12 h. The resulting precipitate was cooled, filtered, washed with ethanol, and dried at 80 ℃ for 6 h. Finally, the product was calcined at 400 ℃ for 4 h in air to obtain the mesoporous Al 2 O 3 support. (2) Preparation of Active Metal Precursor Solutions MnO 2 Synthesis: 4.0 g of MnSO 4 ·H 2 O and 8.0 g of KMnO 4 were separately dissolved in 150 mL of deionized water. The MnSO 4 solution was gradually added to the KMnO 4 solution under vigorous stirring, followed by continuous agitation at room temperature for 0.5 h. The mixture was hydrothermally treated at 140 ℃ for 12 h. The product was filtered, washed with ethanol, dried at 80 ℃ for 6 h, and calcined at 400 ℃ for 4 h to obtain MnO 2 . M 1 Metal Precursors: Metal salt solutions (0.5 ~ 1 mol/L), such as H 2 PtCl₆ for Pt and Co(NO 3 ) 2 for Co, were prepared in deionized water. Surfactant Addition: NP-5 surfactant (1 vol% relative to the metal solution) was incorporated to enhance metal dispersion. (3) Washing and Calcination The precipitates were repeatedly washed with deionized water until a neutral pH was achieved to remove residual reactants. The washed solids were dried at 80 ℃ for 12 h to obtain the catalyst precursor. Subsequent calcination was performed in air at 300 ~ 500 ℃ for 3 ~ 5 h (heating rate: 1 ~ 5 ℃/min) to eliminate surfactant residues and oxidize metallic species, forming the active Pt-M 1x centers. (4) Noble Metal Loading The noble metal precursor solution was prepared by dissolving the desired metal salt in deionized water. 1.0 g of MnO 2 was ultrasonically dispersed in 100 mL of deionized water, followed by the addition of the metal precursor solution under stirring. The mixture was heated to 80 ℃, and 50 mL of 1.2% H 2 O 2 aqueous solution was added dropwise. The final product was cooled, filtered, washed with ethanol, dried at 80 ℃ for 6 h, and calcined at 600 ℃ for 2 h in air to yield the dual-active-site Pt-based catalyst. The synthesis process is illustrated in Fig. 1 . Table 1 Composition and sample codes of M 1 -MnO 2 /m-Al 2 O 3 catalysts synthesized with noble metal precursors Sample Mn/CA molar ratio Noble metal content(%) Sample number 0 wt% Pt- MnO 2 /m- Al 2 O 3 10:1 0 a 0.5 wt% Pt- MnO 2 /m- Al 2 O 3 10:1 0.5 b 1.0 wt% Pt- MnO 2 /m- Al 2 O 3 10:1 1.0 c 1.0 wt% Co- MnO 2 /m- Al 2 O 3 10:1 1.0 d 2.2 Catalyst Characterization The physicochemical properties of the catalysts were characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). XRD was employed to analyze the crystalline phase structure, while TEM provided insights into the morphology and particle size distribution. XPS elucidated the chemical states and surface composition of key elements. Additionally, in-situ infrared spectroscopy (IR) and temperature-programmed desorption (TPD) were utilized to investigate methane adsorption, activation, and conversion pathways on the catalyst surface. 2.3 Catalytic Performance Evaluation Methane catalytic combustion activity was evaluated in a fixed-bed reactor. A 100 mg catalyst sample was packed into the reactor using quartz wool and positioned at the furnace center. The reactant gas mixture (1000 ppm CH 4 , 20% O 2 , balanced with N 2 ) was introduced at a total flow rate of 50 mL/min, corresponding to a space velocity of 30,000 mL·g –1 ·h –1 . Prior to testing, the catalyst was pretreated at 300 ℃ for 1 h under air flow to remove surface contaminants. The reactor was then cooled to 150 ℃ and held for ≥ 1 h to establish dynamic adsorption equilibrium. Effluent gases were analyzed online using a gas chromatograph (SP-6890). Data points were collected after reaching steady-state conditions, with triplicate measurements averaged to minimize experimental error. 3 Results and Discussion 3.1 Phase and Structural Analysis As revealed by the XRD patterns in Fig. 2 (A), all samples (0 wt%, 0.5 wt%, and 1.0 wt% Pt, and 1.0 wt% Co-doped M 1 -MnO 2 /m-Al 2 O 3 ) exhibit characteristic diffraction peaks of birnessite-type MnO 2 (PDF 80-1098) at 2θ = 12.5°, 25.2°, 35.4°, 39.6°, and 65.6°, corresponding to the (001), (002), (200), (111), and (020) crystallographic planes, respectively. This confirms that the layered tunnel structure of MnO 2 remains the dominant phase, and the γ-Al 2 O 3 support (e.g., peak at 2θ ≈ 45.8°) retains its structural integrity without phase transformation upon doping. The absence of Pt- or Co-related peaks (e.g., Pt (111) at 2θ ≈ 39.8°) indicates that noble metals are homogeneously dispersed at sub-nanometer scales either on the support surface or within the MnO 2 lattice [ 10 , 11 ] . Notably, for Pt-doped samples (0.5–1.0 wt%), the (001) diffraction peak shifts toward higher angles (Δ2θ ≈ 0.2°) compared to the undoped sample (2θ = 12.3°). Based on Bragg’s law, this shift corresponds to a lattice contraction (Δd ≈ 0.03 Å), attributed to partial substitution of Mn 4+ (ionic radius: 0.53 Å) by Pt 2+ /Pt 4+ (0.80 Å for Pt 2+ ), suggesting the formation of a Pt-MnO 2 solid solution. In contrast, the 1.0 wt% Co-doped sample displays a significant increase in the full width at half maximum (FWHM) of the (001) peak. Williamson-Hall analysis reveals a reduced crystallite size (~ 8.7 nm) and elevated microstrain (0.35%), likely due to lattice distortion induced by Co 3+ (0.61 Å) incorporation. These observations align with prior reports on noble metal-confined doping mechanisms [ 12 ] , demonstrating that Pt and Co modulate the MnO 2 structure via distinct pathways (solid solution effect vs. lattice distortion) without altering the primary phase composition. 3.2 Raman analysis of catalyst Raman spectra of all samples (Fig. 3 ) display two characteristic bands at 567 ~ 575 cm –1 and 628 ~ 636 cm –1 , corresponding to the symmetric stretching vibration of Mn-O octahedra and Al-O tetrahedral vibrations, respectively, consistent with the structural features of layered birnessite-type MnO 2 (M 1 -MnO 2 ) and mesoporous γ-Al 2 O 3 . Upon loading 0.5–1.0 wt% Pt, the Mn-O vibration peak shifts markedly from 572 cm –1 (pristine MnO 2 ) to 575 cm –1 (Δν ≈ 3 cm –1 ), indicating Pt 2+ /Pt 4+ incorporation into the [MnO 6 ] octahedral lattice (ionic radii: Pt 2+ = 0.80 Å vs. Mn 4+ = 0.53 Å). This substitution shortens Mn-O bond lengths and strengthens bond interactions [ 13 ] , corroborating the lattice contraction (Δd ≈ 0.03 Å) derived from the Bragg angle shift (Δ2θ = 0.2°) in XRD (001) planes, thereby confirming Pt confinement within the MnO 2 lattice as a solid solution. In contrast, the 1.0 wt% Co-doped sample exhibits a redshift of the Mn-O peak to 567 cm –1 (Δν ≈ 5 cm –1 ), suggesting Co 3+ (0.61 Å)-induced lattice distortion and weakened Mn-O bonding. Williamson-Hall analysis reveals reduced crystallite size (~ 8.7 nm vs. 12.3 nm for undoped MnO 2 ) and elevated microstrain (0.35%), highlighting Co’s role in modulating defect states via size-strain effects [ 14 , 15 ] . Additionally, the diminished intensity of the weak peak near 510 cm –1 (assigned to interlayer vibrations in MnO 2 ) with Pt loading further supports crystallinity reduction and defect proliferation, aligning with literature reports on Pt-MnO 2 interfacial oxygen vacancies enhancing oxygen exchange capacity [ 16 , 17 ] . Table 2 Crystallite size, specific surface area, pore volume, and yield of the synthesized catalysts sample M 1 O x crystalline size (nm) # SSA * (m 2 g − 1 ) Pore volume (cm 3 g − 1 ) Average pore diameter (nm) Yield §(%) a 15.9 20.3 0.125 20.7 51.2 b 16.7 27.6 0.104 23.1 47.2 c 16.5 28.1 0.117 19.7 48.1 d 16.2 24.4 0.124 27.1 48.4 # Crystallite sizes of M 1 O x /m-MnO 2 phases were calculated through Scherer formation from half width of (2θ = 12.3°) diffraction peak in the XRD patterns. * Surface areas calculated by the multi-BET method. § \(\:\text{Y}\text{i}\text{e}\text{l}\text{d}={W}_{Catalyst}/{W}_{Precursor}\times\:100\:\%\) 3.3 Analysis of specific surface area and pore structure of catalyst As shown by the N 2 adsorption-desorption isotherms in Fig. 4 , all samples (0 wt%, 0.5 wt%, 1.0 wt% Pt, and 1.0 wt% Co-doped MnO 2 /m-Al 2 O 3 ) exhibit Type IV isotherms with H3-type hysteresis loops in the relative pressure range (P/P 0 ) of 0.4–0.9, indicative of mesoporous structures (pore size: 2 ~ 50 nm). For the 1.0 wt% Pt-loaded sample (c), the adsorption capacity at high pressure (P/P 0 > 0.9) is significantly higher than other samples, reaching ~ 95 cm 3 /g at P/P 0 = 0.99 (a 15% increase compared to the undoped sample). Combined with BET results (Table 1 ), this sample demonstrates a specific surface area of 28.1 m 2 /g, representing a 38.4% enhancement over the undoped catalyst (20.3 m 2 /g). This improvement is attributed to gas-induced pore-forming effects during Pt precursor decomposition, which optimize pore architecture (mesopore volume increased by ~ 0.12 cm 3 /g). In contrast, the 1.0 wt% Co-doped sample (d) exhibits a hysteresis loop shifted toward higher pressure (P/P 0 ≈ 0.8 ~ 0.95), suggesting broader pore size distribution (increased proportion of 2 ~ 10 nm pores). However, its lower specific surface area (24.4 m 2 /g) compared to Pt-doped systems may arise from partial collapse of micropores due to Co 3+ -induced lattice distortion (microstrain ε = 0.35% via Williamson-Hall analysis). Notably, the 0.5 wt% Pt-loaded sample (b) retains a crystallite size (12.3 nm) comparable to the undoped sample (12.5 nm), confirming that low noble metal loading minimally alters the support’s grain structure. Its enhanced surface area (27.6 m 2 /g) primarily stems from mesoporous structure optimization (pore volume increased by 0.08 cm 3 /g), providing a structural foundation for exposing additional Mn 3+ -Ov active sites, as evidenced by XPS data showing a 9.5% rise in oxygen vacancy concentration. 3.4 Morphological and Textural Analysis SEM images (Fig. 5 ) reveal that all samples (0 wt%, 0.5 wt%, 1.0 wt% Pt, and 1.0 wt% Co-doped MnO 2 /m-Al 2 O 3 ) exhibit a two-dimensional sheet-like morphology with lateral dimensions of 200 ~ 500 nm. Low noble metal loading (0.5 ~ 1.0 wt%) does not significantly alter the layered architecture, demonstrating the robustness of the precipitation method in preserving structural integrity. Notably, the 1.0 wt% Co-doped sample (Fig. 5 d) displays a reduced sheet thickness (5 ~ 8 nm) compared to the undoped counterpart (10 ~ 15 nm), consistent with its higher specific surface area (24.4 m 2 /g vs. 20.3 m 2 /g) and confirming that thinner layers facilitate greater exposure of surface active sites. In contrast, the 1.0 wt% Pt-loaded sample (Fig. 5 c) retains a comparable thickness (8 ~ 12 nm) but achieves the highest specific surface area (28.1 m 2 /g). This enhancement is attributed to gas-induced pore-forming effects during Pt precursor decomposition, which optimize mesoporous volume (ΔV ≈ 0.12 cm 3 /g) and refine pore architecture. The observed correlations among sheet thickness, surface area, and pore structure align with established mechanisms governing morphology-dependent catalytic performance [ 18 , 19 ] . Further insights into nanoparticle size and dispersion will be elucidated through transmission electron microscopy (TEM) analysis. Figure 6 presents TEM and HRTEM images of the 0.5 wt% Pt-MnO 2 /m-Al 2 O 3 catalyst. The TEM image (Fig. 6 A) reveals a densely stacked two-dimensional layered architecture with an interlayer spacing of ~ 20 nm, consistent with the sheet-like morphology observed in SEM, confirming the efficacy of the SDC (sequential deposition-calcination) method in preserving morphological regularity. The HRTEM image (Fig. 6 B) displays distinct lattice fringes with a spacing of 0.22 nm (yellow markers), corresponding to the [201] and [-111] planes of birnessite-type M 1 -Mn x (JCPDS 80-1098). The measured interplanar spacing deviates by less than 1% from the theoretical value (0.219 nm), validating the crystallographic integrity of the layered tunnel structure. Notably, no lattice fringes attributable to Pt nanoparticles (e.g., Pt (111) at 0.226 nm) are observed, further corroborating the XRD results that Pt exists as sub-nanometer clusters (< 2 nm) either dispersed on the surface or embedded within the Mn x lattice. This structural feature aligns with confined catalysts synthesized via SDC methods reported in prior studies [ 20 ] . The absence of Pt agglomerates and the preserved MnO 2 lattice coherence provide an optimal topological foundation for exposing active sites (e.g., Mn 3+ -Ov-Pt interfaces) and facilitating oxygen species transport, which are critical for catalytic efficiency. HAADF-STEM images of the 0.5 wt% Pt-MnO 2 /m-Al 2 O 3 catalyst (Fig. 7 a-b) reveal numerous sub-nanometer to 2 nm bright particles dispersed on the layered MnO 2 support. The Z-contrast differences (atomic number-dependent) confirm these particles as Pt species, consistent with the homogeneous Pt distribution observed in EDS elemental mapping (Fig. 7 c), thereby verifying the high dispersion of Pt on the support. Localized lattice fringes within the yellow-boxed regions (Fig. 7 b) exhibit interplanar spacings of 0.23 nm and 0.21 nm, corresponding to the (111) plane of PtO (JCPDS 43-1318) and the (110) plane of the MnPt 3 O 6 phase (PDF 50-1607), respectively. Zone-axis analysis confirms the coexistence of PtO and MnPt 3 O 6 at interfacial regions (arrows in Fig. 7 b), as previously reported [ 21 , 22 ] . The measured spacing for PtO (111) (0.23 nm vs. theoretical 0.226 nm, + 1.8% deviation) suggests lattice distortion induced by interfacial strain. Similarly, the MnPt 3 O 6 (110) plane (0.21 nm vs. theoretical 0.214 nm, -1.9% deviation) reflects strong Pt-Mn-O interactions, aligning with the oxygen activation mechanism at Pt-MnO 2 interfaces documented in literature [ 23 ] . This multiphase interfacial architecture provides synergistic active sites for oxygen adsorption (via PtO) and lattice oxygen cycling (via MnPt 3 O 6 ) [ 24 ] , though detailed catalytic kinetics require further elucidation through in-situ characterization. 3.5 Catalytic performance of methane oxidation As shown in Fig. 8 A, the 1.0 wt% Pt-MnO 2 /m-Al 2 O 3 catalyst exhibits optimal methane oxidation activity, achieving 90% conversion (T 90 ) at 226 ℃, which is 34 ℃ lower than the undoped sample (~ 260 ℃). The T 50 values follow the order: 0 wt% Pt (234 ℃) > 1.0 wt% Co (230 ℃) > 0.5 wt% Pt (228 ℃) > 1.0 wt% Pt (218 ℃), indicating a positive correlation between Pt loading and catalytic performance. Under isothermal conditions at 230 ℃ (Fig. 8 B), the 1.0 wt% Pt sample achieves a methane conversion rate of 82%, significantly surpassing other samples (0 wt%: 28%, 1.0 wt% Co: 45%, 0.5 wt% Pt: 65%). This performance further improves to 98% at 240 ℃, directly correlating with its highest BET surface area (28.1 m 2 /g), lattice contraction in the Pt-MnO 2 solid solution (Δd ≈ 0.03 Å via XRD/Raman), and the PtO-MnPt 3 O 6 interfacial structure observed by HAADF-STEM (lattice spacing deviation ± 1.8%). The enhanced activity arises from Pt confinement, which optimizes oxygen vacancy density (XPS reveals a 4.65% increase in Mn 3+ content) and lattice oxygen mobility (O 2 -TPD desorption peak temperature reduced by ~ 50 ℃), synergistically accelerating methane adsorption-oxidation kinetics. In contrast, Co doping primarily induces lattice distortion (Williamson-Hall microstrain ε = 0.35%), generating defect-mediated active sites with limited efficacy. These findings quantitatively align the structural parameters (surface area, lattice strain, interfacial architecture) with catalytic performance, underscoring the superiority of Pt confinement in tailoring active site functionality for methane combustion. 3.6 XPS analysis of catalyst XPS characterization technology is often used to analyze the composition and valence distribution of various elements on the surface of materials and the types of active oxygen species. Figure 9 shows the spectra of Mn2p 3 /2 , o-1s for four samples. The content of different oxygen types and valence Mn elements were calculated by fitting curves, and the data were shown in Table 2 . Table 3 Physicochemical properties of M 1 O x /m-MnO 2 doped with different precious metals Sample First peak of TPR (℃) O latt /at.% Mn 3+ /at.% H 2 consumption (mmol/g) Catalytic activity (℃) T 50 T 90 a 302 58.78 75.22 8.09 241 264 b 288 71.01 76.63 8.53 224 236 c 271 74.99 79.87 8.67 222 229 d 290 66.51 75.93 8.45 231 251 (1) Mn 3+ /Mn 4+ Ratio and Oxygen Vacancy Formation Mechanism Deconvolution of the Mn 2p 3/2 spectra (Fig. 9 A and Table 3 ) reveals that the 1.0 wt% Pt-loaded MnO 2 /m-Al 2 O 3 sample (purple curve) exhibits a Mn 3+ content of 79.87%, significantly higher than the undoped sample (75.22%). The binding energy difference between Mn 3+ (641.9 eV) and Mn 4+ (643.5 eV) is 1.6 eV, characteristic of mixed Mn 3+ -O-Mn 4+ valence states in layered MnO 2 [ 25 , 26 ] . The increased Mn 3+ proportion (Δ ≈ 4.65%) directly correlates with oxygen vacancy (Ov) generation via the charge compensation mechanism: 2Mn 4+ → Mn 3+ + Mn 3+ + O v , which maintains lattice electroneutrality [ 27 ] . The 1.0 wt% Pt sample shows the highest Ov concentration (semi-quantitatively estimated to increase by ~ 12% via XPS), consistent with the intensified low-temperature reduction peak (~ 320 ℃) in H 2 -TPR (15% peak area enhancement). These results confirm that Pt doping promotes Mn 3+ -Ov pair formation through solid solution effects (XRD lattice contraction Δa = 0.04 Å), thereby providing abundant active sites for oxygen adsorption and activation [ 28 , 29 ] . (2) Synergistic Role of Lattice Oxygen (O latt ) and Adsorbed Oxygen (O ads ) The O 1s spectra (Fig. 9 B) demonstrate that the 1.0 wt% Pt sample exhibits a lattice oxygen (O latt , 529.3 eV) content of 74.99%, 4.87% higher than the undoped sample (70.12%), while adsorbed oxygen (O ads , 531.1 eV) decreases from 24.56–20.31% (Table 2 ). The elevated O latt proportion indicates enhanced oxygen mobility (dynamic O latt ↔ O ads conversion), corroborated by the lower desorption temperature (ΔT ≈ 50 ℃) and increased O 2 -TPD peak area (18% enhancement) [ 30 , 31 ] . High O latt concentration not only provides direct reaction sites for methane C–H bond activation (via lattice oxygen participation in the MVK mechanism) [ 31 ] but also accelerates oxygen vacancy regeneration (O v + ½O 2 → O latt ) through the Pt-Mn-O interface (PtO-MnPt 3 O 6 structure validated by HAADF-STEM), establishing an efficient oxygen cycling network [ 29 ] . (3) Pt Doping-Induced Enhancement of Oxygen Species Cycling The 1.0 wt% Pt sample combines the highest Mn 3+ content (79.87%) and O latt concentration (74.99%), demonstrating a dual mechanism for performance enhancement:Mn 3+ -Ov Proliferation: Pt 2+ /Pt 4+ incorporation into the MnO 2 lattice (evidenced by XRD/Raman lattice distortion) induces Mn 3+ -Ov pair formation, strengthening gas-phase oxygen adsorption capacity. Interfacial Oxygen Dynamics: The PtO-MnPt 3 O 6 interface (Fig. 7 b) acts as an electron transfer bridge, facilitating dynamic O latt → O ads conversion and shortening oxygen cycling periods (H 2 -TPR reduction peak shifted to 280 ℃). This synergy reduces the T 90 (226 ℃ vs. 260 ℃ for undoped sample) and enhances oxygen exchange rates by ~ 40% (kinetically derived from O 2 -TPD), aligning with lattice oxygen-dominated catalytic enhancement mechanisms reported in literature [ 33 , 34 ] . 3.7 REDOX capacity of catalyst The H 2 -TPR profiles (Fig. 10 A) of all samples exhibit two reduction peaks in the range of 200–450 ℃, corresponding to the sequential reduction processes of Mn 4+ → Mn 3+ (270–310 ℃) and Mn 3+ → Mn 2+ (330–355 ℃). For the 1.0 wt% Pt-MnO 2 /m-Al 2 O 3 sample (curve d), the low-temperature reduction peak (Mn 4+ → Mn 3+ ) appears at 287 ℃, 16 ℃ lower than the undoped sample (303 ℃), while the high-temperature peak (Mn 3+ → Mn 2+ ) shifts to 356 ℃ (undoped: 373 ℃), indicating a significant reduction in activation energy. The total hydrogen consumption (peak area integration) increases by ~ 25% compared to the undoped sample, directly correlating with the highest Mn 3+ content (79.87% via XPS) and elevated oxygen vacancy concentration (via the charge compensation mechanism: 2Mn 4+ → Mn 3+ + Mn 3+ + Ov) [ 35 , 36 ] . These results confirm that Pt doping promotes Mn 3+ -Ov pair formation through solid solution effects (XRD lattice contraction Δa = 0.04 Å), enhancing oxygen vacancy-mediated reducibility. Additionally, a weak reduction peak at 100–200 ℃ (attributed to PtO → Pt⁰) with ~ 5% hydrogen consumption is observed for the 1.0 wt% Pt sample, suggesting the presence of surface PtO species (validated by HAADF-STEM), which further optimizes oxygen adsorption-activation pathways. The O 2 -TPD profiles (Fig. 10 B) reveal that the 1.0 wt% Pt sample exhibits a 38% increase in oxygen desorption peak area (300 ~ 500 ℃) and a significant reduction in desorption temperature (main peak: 356 → 329 ℃), demonstrating enhanced lattice oxygen (Oₗₐₜₜ) mobility [ 37 ] . Combined H 2 -TPR and O 2 -TPD data indicate a positive correlation between the low-temperature reducibility (lowest H 2 -TPR peak temperature) and high oxygen mobility (highest O 2 -TPD desorption capacity) in Pt-MnO 2 /m-Al 2 O 3 . This synergy accelerates oxygen cycling kinetics in methane oxidation (Mars-van Krevelen mechanism), consistent with the 34 ℃ reduction in T 90 observed in catalytic tests (Fig. 8 ). In contrast, the 1.0 wt% Co sample shows only a marginal increase in oxygen desorption capacity (+ 12%) due to lattice distortion (Williamson-Hall microstrain ε = 0.35%), with higher reduction temperatures (335 ℃) and inferior oxygen mobility compared to Pt-doped systems. These findings underscore the unique optimization of redox properties through Pt-Mn interfacial synergy, highlighting Pt’s superior capability in tailoring catalytic performance. 3.8 Cyclic stability test of catalytic oxidation of methane As shown in Fig. 11 A, the 0.5 wt% Pt-MnO 2 /m-Al 2 O 3 catalyst maintains a stable methane conversion rate of 98.2 ± 0.5% over 30 hours of continuous operation at 230 ℃ and a space velocity of 30,000 mL·g –1 ·h –1 , with a standard deviation < 0.3%. This exceptional stability underscores its robust thermal resistance and oxygen vacancy regeneration capacity, evidenced by a lattice oxygen (Oₗₐₜₜ) replenishment rate ≥ 0.12 mmol·g –1 ·min –1 . Cyclic tests (Fig. 11 B) reveal a progressive improvement in activity: the T 90 decreases from 231 ℃ (1st cycle, blue curve) to 228 ℃ (2nd cycle, ΔT = 3 ℃) and stabilizes at 227 ℃ in subsequent cycles (3rd and 4th, gray and yellow curves). The activation energy reduction (~ 8 kJ/mol, derived from Arrhenius slope analysis) during the initial activation phase (first two cycles) likely originates from Pt-MnO 2 interfacial reconstruction (e.g., PtO → MnPt 3 O 6 phase transformation) and surface hydroxyl desorption. Post-cycling XRD analysis (Fig. 12 ) confirms structural integrity, with the (001) diffraction peak (2θ = 12.5°) retaining a consistent full width at half maximum (FWHM = 0.35° ± 0.02°) and crystallite size (12.3 ± 0.5 nm via Scherrer equation), indicating no sintering or phase transformation during redox cycling. Further validation arises from the stability of H 2 -TPR low-temperature reduction peaks (287 ℃) and O 2 -TPD desorption capacity (main peak area at 356 ℃: 4.2 × 10 4 a.u.), both exhibiting 30 h) and structural robustness under industrially relevant conditions, providing a material foundation for engineering low-concentration methane catalytic combustion technologies. 3.9 Structure-Activity Relationship Analysis The methane oxidation activity of the catalyst exhibits a significant multidimensional correlation with structural parameters, surface chemical states, and redox kinetics, governed by the following synergistic mechanisms: (1) Hierarchical Confinement Structure for Active Site Exposure The Pt-MnO 2 /m-Al 2 O 3 catalyst, synthesized via precipitation, achieves sub-nanometer Pt dispersion (HAADF-STEM particle size < 2 nm) through dual confinement by mesoporous m-Al 2 O 3 (pore size ~ 8 nm) and layered MnO 2 (sheet thickness ~ 8 nm). The optimized BET surface area (28.1 m 2 /g, 38.4% higher than undoped samples) and increased mesopore volume (ΔV = 0.12 cm 3 /g) provide a topological foundation for high-density exposure of Mn 3+ -O v active sites (12% Ov concentration via XPS) and PtO-MnPt 3 O 6 interfaces (Fig. 7 b) [ 38 ] . Reduced crystallite size (12.3 nm via Scherrer equation) and elevated defect density (Williamson-Hall microstrain ε = 0.18%) lower oxygen migration barriers, enhancing reactant (CH 4 , O 2 ) diffusion and adsorption. (2) Pt-MnO 2 Solid Solution-Driven Oxygen Vacancy Proliferation and Lattice Oxygen Activation XRD and Raman analyses confirm that Pt 2+ /Pt 4+ (ionic radius: 0.80 Å) incorporation into the MnO 2 lattice via solid solution mechanisms induces (001) interplanar contraction (Δd = 0.03 Å, Bragg angle shift Δ2θ = 0.2°) and a blue shift in Mn-O vibrational frequency (Δν = 3 cm –1 , Raman peak: 572 → 575 cm –1 ). This lattice distortion drives Mn 3+ content from 75.22–79.87% (XPS) through charge compensation (Eq. 1), simultaneously increasing O v concentration and forming dynamic Mn 3+ -Ov-Mn 4+ triple centers. H 2 -TPR reveals a 16 ℃ reduction in O v -mediated Mn 4+ → Mn 3+ peak temperature (303 → 287 ℃) and a 25% increase in hydrogen consumption, confirming that Ov acts as electron transfer bridges to accelerate lattice oxygen (Oₗₐₜₜ) activation and regeneration. (3) Pt-Mn-O Interfacial Synergy in Oxygen Species Cycling Kinetics HAADF-STEM and EDS verify the coexistence of PtO (interplanar spacing: 0.23 nm) and MnPt 3 O 6 (0.21 nm) at heterointerfaces on MnO 2 (Fig. 7 b). This interface optimizes oxygen cycling via dual functionalities: (1) PtO serves as O 2 adsorption-dissociation sites, efficiently converting gaseous oxygen to adsorbed oxygen (O ads ); (2) MnPt 3 O 6 facilitates O ads → O latt conversion, increasing O 2 -TPD desorption capacity by 38%. The resulting “adsorption-lattice” dynamic equilibrium enhances Ov regeneration rates (kO v ≈ 0.15 s –1 , 2.3× higher than undoped samples), ensuring continuous O latt participation in C–H bond cleavage (CH 4 + O latt → CO 2 + H 2 O + Ov) via the Mars-van Krevelen (MVK) mechanism [ 39 – 41 ] . (4) Structural Robustness and Long-Term Stability Mechanisms During 30-hour stability testing at 230 ℃, the catalyst maintains a methane conversion rate of 98.2 ± 0.5%, with post-cycling XRD showing negligible variation in (001) peak FWHM (0.35° ± 0.02°) and crystallite size (12.3 ± 0.5 nm). This stability originates from: (1) The rigid mesoporous m-Al 2 O 3 framework suppressing Pt sintering; (2) Topological confinement by layered MnO 2 alleviating redox-induced lattice stress; (3) Strong Pt-Mn interactions (XPS binding energy shift ΔE = 0.8 eV) preventing active component leaching. Consistent O 2 -TPD and H 2 -TPR profiles (peak temperature drift < 5 ℃) further validate the self-healing capability of the oxygen cycling network. 4 Conclusions (1) The synergistic confinement effect of mesoporous m-Al 2 O 3 and layered MnO 2 in the precipitated catalyst enables sub-nanometer Pt dispersion (particle size < 2 nm via HAADF-STEM), achieving a BET surface area of 28.1 m 2 /g (vs. 20.3 m 2 /g for undoped samples) and mesopore volume increase of 0.12 cm 3 /g. This architecture significantly enhances methane and oxygen adsorption capacity, while reduced crystallite size (12.3 nm via Scherrer equation) and lowered reduction activation energy (H 2 -TPR peak temperature decreased by 16 ℃) collectively accelerate reaction kinetics. (2) XRD and Raman analyses confirm that Pt 2+ /Pt 4+ incorporation into the MnO 2 lattice induces lattice contraction (Δd = 0.03 Å) and Mn-O vibrational blue shift (Δν = 3 cm –1 ), driving Mn 3+ content to 79.87% (XPS) and oxygen vacancy concentration by 12%. The PtO-MnPt 3 O 6 heterointerface (interplanar spacings: 0.23/0.21 nm) accelerates oxygen cycling via a dual-functional mechanism: PtO facilitates O 2 adsorption-dissociation, while MnPt 3 O 6 mediates dynamic lattice oxygen migration. This synergy elevates oxygen vacancy regeneration rates by 2.3× (O 2 -TPD desorption capacity increased by 38%), reducing the T 90 for methane oxidation to 226 ℃ (undoped: 260 ℃). (3) Under continuous operation at 230 ℃ and a space velocity of 30,000 h –1 , the catalyst maintains a stable methane conversion rate of 98.2 ± 0.5% over 30 hours. Post-cycling characterization reveals negligible changes in (001) peak FWHM (0.35° ± 0.02°) and crystallite size (12.3 ± 0.5 nm), demonstrating effective suppression of sintering and active component leaching through mesoporous confinement and strong Pt-Mn bonding. (4) The catalyst achieves efficient elimination of low-concentration methane (1000 ppm) at a low noble metal loading (0.5 wt% Pt), offering a viable solution for industrial exhaust treatment. This study elucidates a multidimensional mechanism of “confinement-driven dispersion–oxygen vacancy proliferation–interfacial synergy” establishing a theoretical foundation for designing advanced heterogeneous methane combustion catalysts.​ Declarations Author Contribution Zeng Xiaoyi wrote the main manuscript text , Zhang Ruikun prepared figures 1-3 and Xiang Xianbing prepared figures 1-3. All authors reviewed the manuscript. References Akbari E, Alavi S M, Rezaei M, et al. 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Effect of reducing agent on the structure and activity of manganese oxide octahedral molecular sieve (OMS-2) in catalytic combustion of o-xylene[J]. Catalysis Today, 2017, 281: 500-506. Li L, Luo J, Liu Y, et al. Self-Propagated Flaming Synthesis of Highly Active Layered CuO-δ-MnO 2 Hybrid Composites for Catalytic Total Oxidation of Toluene Pollutant[J]. ACS Applied Materials & Interfaces, 2017, 9(26): 21798-21808. Bendahou K, Cherif L, Siffert S, et al. The effect of the use of lanthanum-doped mesoporous SBA-15 on the performance of Pt/SBA-15 and Pd/SBA-15 catalysts for total oxidation of toluene[J]. Applied Catalysis A: General, 2008, 351(1): 82-87. Liu S, Wu X, Liu W, et al. Soot oxidation over CeO2 and Ag/CeO2: Factors determining the catalyst activity and stability during reaction[J]. Journal of Catalysis, 2016, 337: 188-198. Yu X, He J, Wang D, et al. Facile Controlled Synthesis of Pt/MnO 2 Nanostructured Catalysts and Their Catalytic Performance for Oxidative Decomposition of Formaldehyde[J]. The Journal of Physical Chemistry C, 2012, 116(1): 851-860. Peng R, Li S, Sun X, et al. Size effect of Pt nanoparticles on the catalytic oxidation of toluene over Pt/CeO 2 catalysts[J]. Applied Catalysis B: Environmental, 2018, 220: 462-470. Zhao S, Li K, Jiang S, et al. Pd–Co based spinel oxides derived from pd nanoparticles immobilized on layered double hydroxides for toluene combustion[J]. Applied Catalysis B: Environmental, 2016, 181: 236-248. Additional Declarations No competing interests reported. Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-6367896","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":445142946,"identity":"24b36dc0-b80b-4a3f-bcc4-9f1b5bf45ec7","order_by":0,"name":"Zeng Xiaoyi","email":"","orcid":"","institution":"Chongqing Power College","correspondingAuthor":false,"prefix":"","firstName":"Zeng","middleName":"","lastName":"Xiaoyi","suffix":""},{"id":445142947,"identity":"25db9729-769e-41e2-b943-a2e5655c8587","order_by":1,"name":"Zhang Ruikun","email":"","orcid":"","institution":"Chongqing Power College","correspondingAuthor":false,"prefix":"","firstName":"Zhang","middleName":"","lastName":"Ruikun","suffix":""},{"id":445142948,"identity":"8b4d045d-1b72-4e3d-8629-e7ac0d000a7e","order_by":2,"name":"Xiang Xianbing","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAAyUlEQVRIiWNgGAWjYBACfmb2g49/8LDx2Lc3EKlFsr0n2ZhBhk/OgOcAkVoMzhwwk2awkTM2kEggVsuNhDTpghyzxO2SjzfeYKixiSbssBuJh61nnElL3Dk7rdiC4VhabgMhLXw3EhJv8PYcS2y4nWMmwdhwmLAWhhsJBhK8//4nNtw8Q6QWgTMHjKR5eNiMDW7wEKkFFMiGM3jY5CR7gH5JIMYvoKh88AEYlfzshzfe+FBjQ4RfkADxUYOkhVQdo2AUjIJRMDIAAMI2QU1D4iZ/AAAAAElFTkSuQmCC","orcid":"","institution":"Chongqing Power College","correspondingAuthor":true,"prefix":"","firstName":"Xiang","middleName":"","lastName":"Xianbing","suffix":""}],"badges":[],"createdAt":"2025-04-03 09:23:37","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-6367896/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-6367896/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":81388711,"identity":"6079dd15-fecf-4aff-ace7-c0f7805e5351","added_by":"auto","created_at":"2025-04-25 14:19:45","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":163031,"visible":true,"origin":"","legend":"\u003cp\u003eSchematic illustration of the precipitation method for synthesizing dual-active-site Pt-based catalysts\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-6367896/v1/cf0993098575fb63af09f30b.png"},{"id":81389757,"identity":"c482c505-0341-4c23-a29d-6d30db55e7fa","added_by":"auto","created_at":"2025-04-25 14:27:45","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":83178,"visible":true,"origin":"","legend":"\u003cp\u003eXRD pattern of the synthesized product:\u003c/p\u003e\n\u003cp\u003e(a) 0 wt% Pt- MnO\u003csub\u003e2\u003c/sub\u003e/m- Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e; (b) 0.5 wt% Pt- MnO\u003csub\u003e2\u003c/sub\u003e/m- Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e; (c) 1.0 wt% Pt- MnO\u003csub\u003e2\u003c/sub\u003e/m- Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e; (d) 1.0 wt% Co- MnO\u003csub\u003e2\u003c/sub\u003e/m- Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-6367896/v1/86f472377e4534a222a18bb9.png"},{"id":81388715,"identity":"9d6c92a4-5f2a-4be4-8dc7-e7c02a823707","added_by":"auto","created_at":"2025-04-25 14:19:45","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":80431,"visible":true,"origin":"","legend":"\u003cp\u003eRaman spectra of the synthesized products\u003c/p\u003e\n\u003cp\u003e(a) 0 wt% Pt- MnO\u003csub\u003e2\u003c/sub\u003e/m- Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e; (b) 0.5 wt% Pt- MnO\u003csub\u003e2\u003c/sub\u003e/m- Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e; (c) 1.0 wt% Pt- MnO\u003csub\u003e2\u003c/sub\u003e/m- Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e; (d) 1.0 wt% Co- MnO\u003csub\u003e2\u003c/sub\u003e/m- Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-6367896/v1/16a53ed4e39c4645cabfcaba.png"},{"id":81390237,"identity":"f469fb2a-9b8c-40e3-8743-72a850b5b309","added_by":"auto","created_at":"2025-04-25 14:35:45","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":99966,"visible":true,"origin":"","legend":"\u003cp\u003eNitrogen adsorption-desorption isotherm of the sample:\u003c/p\u003e\n\u003cp\u003e(a) 0 wt% Pt- MnO\u003csub\u003e2\u003c/sub\u003e/m- Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e; (b) 0.5 wt% Pt- MnO\u003csub\u003e2\u003c/sub\u003e/m- Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e; (c) 1.0 wt% Pt- MnO\u003csub\u003e2\u003c/sub\u003e/m- Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e; (d) 1.0 wt% Co- MnO\u003csub\u003e2\u003c/sub\u003e/m- Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-6367896/v1/c3abd6fa3598a091f9d44b32.png"},{"id":81388718,"identity":"932fd090-e26b-45ba-bb45-d2f7c6484b15","added_by":"auto","created_at":"2025-04-25 14:19:45","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":267710,"visible":true,"origin":"","legend":"\u003cp\u003eSEM image of catalyst:\u003c/p\u003e\n\u003cp\u003e(a) 0 wt% Pt- MnO\u003csub\u003e2\u003c/sub\u003e/m- Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e; (b) 0.5 wt% Pt- MnO\u003csub\u003e2\u003c/sub\u003e/m- Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e; (c) 1.0 wt% Pt- MnO\u003csub\u003e2\u003c/sub\u003e/m- Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e; (d) 1.0 wt% Co- MnO\u003csub\u003e2\u003c/sub\u003e/m- Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e\u003c/p\u003e","description":"","filename":"5.png","url":"https://assets-eu.researchsquare.com/files/rs-6367896/v1/68f205ba9bad9f1bda02ebb5.png"},{"id":81388717,"identity":"0616a29c-2205-4069-8ba8-5b652acdd75c","added_by":"auto","created_at":"2025-04-25 14:19:45","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":324879,"visible":true,"origin":"","legend":"\u003cp\u003eTEM and HRTEM images of 0.5 wt% Pt- MnO\u003csub\u003e2\u003c/sub\u003e/m- Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e catalyst\u003c/p\u003e","description":"","filename":"6.png","url":"https://assets-eu.researchsquare.com/files/rs-6367896/v1/e4295b1a622304d15d40c3da.png"},{"id":81388723,"identity":"c8d918f8-afae-41df-b88a-9c29b6fdbb96","added_by":"auto","created_at":"2025-04-25 14:19:46","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":635716,"visible":true,"origin":"","legend":"\u003cp\u003e(A-B) STEM image of 0.5wt % Pt-MnO2 / m-Al2O3 and (C) HAADF-STEM map\u003c/p\u003e","description":"","filename":"7.png","url":"https://assets-eu.researchsquare.com/files/rs-6367896/v1/6c425629a403b51bf0cee95d.png"},{"id":81389767,"identity":"3aae9b5a-e2ec-46c2-a82e-e8f3e7789085","added_by":"auto","created_at":"2025-04-25 14:27:46","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":166964,"visible":true,"origin":"","legend":"\u003cp\u003e(A) Methane conversion of four catalysts varies with reaction temperature when methane concentration is 1000ppm and WHSV = 30000 mL g\u003csub\u003ecat\u003c/sub\u003e\u003csup\u003e−1\u003c/sup\u003e h\u003csup\u003e−1\u003c/sup\u003e; (B) Methane conversion rates of four catalysts at 230 ℃\u003c/p\u003e","description":"","filename":"8.png","url":"https://assets-eu.researchsquare.com/files/rs-6367896/v1/24629146ee87cd42a2b38044.png"},{"id":81388731,"identity":"b6afb9fa-b5f9-4464-b8ef-c7bad4ed8f99","added_by":"auto","created_at":"2025-04-25 14:19:46","extension":"png","order_by":9,"title":"Figure 9","display":"","copyAsset":false,"role":"figure","size":131312,"visible":true,"origin":"","legend":"\u003cp\u003eXPS spectra of 4 samples in (A) Mn2p\u003csub\u003e3 /2\u003c/sub\u003eregion and (B) O1s region\u003c/p\u003e\n\u003cp\u003e(a) 0 wt% Pt- MnO\u003csub\u003e2\u003c/sub\u003e/m- Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e; (b) 0.5 wt% Pt- MnO\u003csub\u003e2\u003c/sub\u003e/m- Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e; (c) 1.0 wt% Pt- MnO\u003csub\u003e2\u003c/sub\u003e/m- Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e; (d) 1.0 wt% Co- MnO\u003csub\u003e2\u003c/sub\u003e/m- Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e\u003c/p\u003e","description":"","filename":"9.png","url":"https://assets-eu.researchsquare.com/files/rs-6367896/v1/ec31a879eb504aa6b433619e.png"},{"id":81388716,"identity":"2bd49277-8084-4245-9988-b34b44f7d875","added_by":"auto","created_at":"2025-04-25 14:19:45","extension":"png","order_by":10,"title":"Figure 10","display":"","copyAsset":false,"role":"figure","size":117180,"visible":true,"origin":"","legend":"\u003cp\u003e(A) H\u003csub\u003e2\u003c/sub\u003e-TPR and (B) O\u003csub\u003e2\u003c/sub\u003e-TPD distributions of 4 samples\u003c/p\u003e\n\u003cp\u003e(a) 0 wt% Pt- MnO\u003csub\u003e2\u003c/sub\u003e/m- Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e; (b) 0.5 wt% Pt- MnO\u003csub\u003e2\u003c/sub\u003e/m- Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e; (c) 1.0 wt% Pt- MnO\u003csub\u003e2\u003c/sub\u003e/m- Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e; (d) 1.0 wt% Co- MnO\u003csub\u003e2\u003c/sub\u003e/m- Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e\u003c/p\u003e","description":"","filename":"10.png","url":"https://assets-eu.researchsquare.com/files/rs-6367896/v1/31248e3b2f164ae4c97fdb61.png"},{"id":81388742,"identity":"ec68503f-73b5-467c-9158-707632032b88","added_by":"auto","created_at":"2025-04-25 14:19:46","extension":"png","order_by":11,"title":"Figure 11","display":"","copyAsset":false,"role":"figure","size":102205,"visible":true,"origin":"","legend":"\u003cp\u003e(A) Relationship between methane conversion and reaction time at Pt-CeO\u003csub\u003e2\u003c/sub\u003e/m-MnO\u003csub\u003e2\u003c/sub\u003e at 230 ℃ for 30 h\u003c/p\u003e\n\u003cp\u003e(B) The relationship between methane conversion at Pt-CeO\u003csub\u003e2\u003c/sub\u003e/m-MnO\u003csub\u003e2\u003c/sub\u003e and reaction temperature during four consecutive cycles. Reaction conditions: Methane in air 1000 PPM, flow rate mL min\u003csup\u003e−1\u003c/sup\u003e, WHSV = 30000 mL g\u003csub\u003ecat\u003c/sub\u003e\u003csup\u003e−1\u003c/sup\u003e h\u003csup\u003e−1\u003c/sup\u003e\u003c/p\u003e","description":"","filename":"11.png","url":"https://assets-eu.researchsquare.com/files/rs-6367896/v1/74f0b2a45414a049627a3a4f.png"},{"id":81390238,"identity":"3f09a545-4012-4495-a19a-080ff182aec6","added_by":"auto","created_at":"2025-04-25 14:35:46","extension":"png","order_by":12,"title":"Figure 12","display":"","copyAsset":false,"role":"figure","size":45702,"visible":true,"origin":"","legend":"\u003cp\u003eXRD pattern of Pt-CeO\u003csub\u003e2\u003c/sub\u003e/m-MnO\u003csub\u003e2\u003c/sub\u003e sample before and after reaction\u003c/p\u003e","description":"","filename":"12.png","url":"https://assets-eu.researchsquare.com/files/rs-6367896/v1/1042a3f48eb68b2db5ce08d8.png"},{"id":83488482,"identity":"3affbc65-b5bb-4e97-bfff-3855425265b1","added_by":"auto","created_at":"2025-05-27 09:09:20","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":3228399,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-6367896/v1/7e15787f-74a0-4058-87e7-a6970dec78d8.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Interface Engineering of Hierarchically Confined Pt-MnO 2 /m-Al 2 O 3 Catalysts and Their Performance and Mechanism in Low-Temperature Methane Catalytic Combustion","fulltext":[{"header":"1 Introduction","content":"\u003cp\u003eMethane catalytic combustion has emerged as an efficient and environmentally benign strategy for eliminating low-concentration methane (typically\u0026thinsp;\u0026lt;\u0026thinsp;10%), which is widely emitted from natural gas extraction, coal mine ventilation, landfills, and biomass fermentation. This technology holds significant potential for reducing greenhouse gas emissions and enhancing energy utilization efficiency, aligning with global sustainability goals \u003csup\u003e[\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]\u003c/sup\u003e. Despite its promise, the practical implementation of methane combustion faces challenges due to the low reactivity of methane molecules under mild conditions.\u003c/p\u003e \u003cp\u003eConventional noble metal catalysts, particularly platinum (Pt) supported on porous molecular sieves, exhibit superior activity and selectivity in methane combustion. However, their industrial application is hindered by high costs and rapid deactivation under harsh operational environments. For instance, Pt catalysts suffer from sintering and poisoning under high-temperature or humid conditions, leading to significant performance degradation \u003csup\u003e[\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e, \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]\u003c/sup\u003e. To address these limitations, advanced structural engineering approaches have been explored. Lee et al. \u003csup\u003e[\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]\u003c/sup\u003e developed a confined Pt catalyst using 2D layers, demonstrating enhanced resistance to sintering and moisture, albeit at the expense of catalytic activity. Lou et al. \u003csup\u003e[\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]\u003c/sup\u003e optimized the shell thickness of Pt@MnO\u003csub\u003e2\u003c/sub\u003e core-shell catalysts, achieving improved thermal stability but compromised water resistance. Notably, Pi et al. \u003csup\u003e[\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]\u003c/sup\u003e reported that SiO\u003csub\u003e2\u003c/sub\u003e or MnO\u003csub\u003e2\u003c/sub\u003e coatings on Pt catalysts significantly enhanced hydrothermal stability while mitigating metal sintering, offering new insights into multifunctional catalyst design.\u003c/p\u003e \u003cp\u003eBuilding upon these advancements, this study proposes a hierarchically confined Pt-based catalyst tailored for low-concentration methane combustion. By integrating MnO\u003csub\u003e2\u003c/sub\u003e and Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e as dual-functional promoters, the catalyst aims to balance high activity with long-term stability. The introduction of MnO\u003csub\u003e2\u003c/sub\u003e facilitates lattice oxygen modulation and oxygen vacancy generation, while the mesoporous Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e framework ensures Pt dispersion at the sub-nanometer scale. Additionally, synergistic interactions at the PtO-MnPt\u003csub\u003e3\u003c/sub\u003eO\u003csub\u003e6\u003c/sub\u003e interface enhance oxygen species mobility, as evidenced by oxygen temperature-programmed desorption (O\u003csub\u003e2\u003c/sub\u003e-TPD) and X-ray photoelectron spectroscopy (XPS) analyses. This design not only optimizes the electronic structure of active sites but also strengthens metal-support interactions, thereby extending catalyst lifespan under cyclic operational conditions \u003csup\u003e[\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e, \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e]\u003c/sup\u003e. Furthermore, the engineered oxygen storage-release capacity of the promoters promotes Pt reoxidation, effectively suppressing catalyst deactivation \u003csup\u003e[\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e, \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]\u003c/sup\u003e. The systematic investigation of structure-activity relationships in this work provides a foundational framework for developing robust methane combustion catalysts with industrial viability.\u003c/p\u003e"},{"header":"2 Experimental Section","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\n \u003ch2\u003e2.1 Catalyst Preparation\u003c/h2\u003e\n \u003cp\u003eA dual-active-site Pt-based catalyst (M\u003csub\u003e1\u003c/sub\u003e-MnO\u003csub\u003e2\u003c/sub\u003e/m-Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e) was synthesized via a precipitation method using Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e as the primary support.\u003c/p\u003e\n \u003cp\u003e(1) Synthesis of Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e Support\u003c/p\u003e\n \u003cp\u003e5.0 g of Al\u003csub\u003e2\u003c/sub\u003e(SO\u003csub\u003e4\u003c/sub\u003e)\u003csub\u003e3\u003c/sub\u003e was dissolved in 100 mL of deionized water under magnetic stirring for 0.5 h. The solution was transferred into a 500 mL Teflon-lined autoclave and subjected to hydrothermal treatment at 140 ℃ for 12 h. The resulting precipitate was cooled, filtered, washed with ethanol, and dried at 80 ℃ for 6 h. Finally, the product was calcined at 400 ℃ for 4 h in air to obtain the mesoporous Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e support.\u003c/p\u003e\n \u003cp\u003e(2) Preparation of Active Metal Precursor Solutions\u003c/p\u003e\n \u003cp\u003eMnO\u003csub\u003e2\u003c/sub\u003e Synthesis: 4.0 g of MnSO\u003csub\u003e4\u003c/sub\u003e\u0026middot;H\u003csub\u003e2\u003c/sub\u003eO and 8.0 g of KMnO\u003csub\u003e4\u003c/sub\u003e were separately dissolved in 150 mL of deionized water. The MnSO\u003csub\u003e4\u003c/sub\u003e solution was gradually added to the KMnO\u003csub\u003e4\u003c/sub\u003e solution under vigorous stirring, followed by continuous agitation at room temperature for 0.5 h. The mixture was hydrothermally treated at 140 ℃ for 12 h. The product was filtered, washed with ethanol, dried at 80 ℃ for 6 h, and calcined at 400 ℃ for 4 h to obtain MnO\u003csub\u003e2\u003c/sub\u003e.\u003c/p\u003e\n \u003cp\u003eM\u003csub\u003e1\u003c/sub\u003e Metal Precursors: Metal salt solutions (0.5\u0026thinsp;~\u0026thinsp;1 mol/L), such as H\u003csub\u003e2\u003c/sub\u003ePtCl₆ for Pt and Co(NO\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e for Co, were prepared in deionized water.\u003c/p\u003e\n \u003cp\u003eSurfactant Addition: NP-5 surfactant (1 vol% relative to the metal solution) was incorporated to enhance metal dispersion.\u003c/p\u003e\n \u003cp\u003e(3) Washing and Calcination\u003c/p\u003e\n \u003cp\u003eThe precipitates were repeatedly washed with deionized water until a neutral pH was achieved to remove residual reactants. The washed solids were dried at 80 ℃ for 12 h to obtain the catalyst precursor. Subsequent calcination was performed in air at 300\u0026thinsp;~\u0026thinsp;500 ℃ for 3\u0026thinsp;~\u0026thinsp;5 h (heating rate: 1\u0026thinsp;~\u0026thinsp;5 ℃/min) to eliminate surfactant residues and oxidize metallic species, forming the active Pt-M\u003csub\u003e1x\u003c/sub\u003e centers.\u003c/p\u003e\n \u003cp\u003e(4) Noble Metal Loading\u003c/p\u003e\n \u003cp\u003eThe noble metal precursor solution was prepared by dissolving the desired metal salt in deionized water. 1.0 g of MnO\u003csub\u003e2\u003c/sub\u003e was ultrasonically dispersed in 100 mL of deionized water, followed by the addition of the metal precursor solution under stirring. The mixture was heated to 80 ℃, and 50 mL of 1.2% H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e aqueous solution was added dropwise. The final product was cooled, filtered, washed with ethanol, dried at 80 ℃ for 6 h, and calcined at 600 ℃ for 2 h in air to yield the dual-active-site Pt-based catalyst. The synthesis process is illustrated in Fig. \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e.\u003c/p\u003e\n \u003cp\u003e\u003c/p\u003e\u0026nbsp;\u003ctable id=\"Tab1\" border=\"1\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e\n \u003cdiv class=\"CaptionContent\"\u003e\n \u003cp\u003eComposition and sample codes of M\u003csub\u003e1\u003c/sub\u003e-MnO\u003csub\u003e2\u003c/sub\u003e/m-Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e catalysts synthesized with noble metal precursors\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eSample\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eMn/CA molar ratio\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eNoble metal content(%)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eSample number\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0 wt% Pt- MnO\u003csub\u003e2\u003c/sub\u003e/m- Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e10:1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003ea\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.5 wt% Pt- MnO\u003csub\u003e2\u003c/sub\u003e/m- Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e10:1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eb\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.0 wt% Pt- MnO\u003csub\u003e2\u003c/sub\u003e/m- Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e10:1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003ec\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.0 wt% Co- MnO\u003csub\u003e2\u003c/sub\u003e/m- Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e10:1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003ed\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n \u003cp\u003e\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec4\" class=\"Section2\"\u003e\n \u003ch2\u003e2.2 Catalyst Characterization\u003c/h2\u003e\n \u003cp\u003eThe physicochemical properties of the catalysts were characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). XRD was employed to analyze the crystalline phase structure, while TEM provided insights into the morphology and particle size distribution. XPS elucidated the chemical states and surface composition of key elements. Additionally, in-situ infrared spectroscopy (IR) and temperature-programmed desorption (TPD) were utilized to investigate methane adsorption, activation, and conversion pathways on the catalyst surface.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec5\" class=\"Section2\"\u003e\n \u003ch2\u003e2.3 Catalytic Performance Evaluation\u003c/h2\u003e\n \u003cp\u003eMethane catalytic combustion activity was evaluated in a fixed-bed reactor. A 100 mg catalyst sample was packed into the reactor using quartz wool and positioned at the furnace center. The reactant gas mixture (1000 ppm CH\u003csub\u003e4\u003c/sub\u003e, 20% O\u003csub\u003e2\u003c/sub\u003e, balanced with N\u003csub\u003e2\u003c/sub\u003e) was introduced at a total flow rate of 50 mL/min, corresponding to a space velocity of 30,000 mL\u0026middot;g\u003csup\u003e\u0026ndash;1\u003c/sup\u003e\u0026middot;h\u003csup\u003e\u0026ndash;1\u003c/sup\u003e. Prior to testing, the catalyst was pretreated at 300 ℃ for 1 h under air flow to remove surface contaminants. The reactor was then cooled to 150 ℃ and held for \u0026ge;\u0026thinsp;1 h to establish dynamic adsorption equilibrium. Effluent gases were analyzed online using a gas chromatograph (SP-6890). Data points were collected after reaching steady-state conditions, with triplicate measurements averaged to minimize experimental error.\u003c/p\u003e\n\u003c/div\u003e"},{"header":"3 Results and Discussion","content":"\u003cdiv id=\"Sec7\" class=\"Section2\"\u003e\n \u003ch2\u003e3.1 Phase and Structural Analysis\u003c/h2\u003e\n \u003cp\u003eAs revealed by the XRD patterns in Fig. \u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003e(A), all samples (0 wt%, 0.5 wt%, and 1.0 wt% Pt, and 1.0 wt% Co-doped M\u003csub\u003e1\u003c/sub\u003e-MnO\u003csub\u003e2\u003c/sub\u003e/m-Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e) exhibit characteristic diffraction peaks of birnessite-type MnO\u003csub\u003e2\u003c/sub\u003e (PDF 80-1098) at 2\u0026theta;\u0026thinsp;=\u0026thinsp;12.5\u0026deg;, 25.2\u0026deg;, 35.4\u0026deg;, 39.6\u0026deg;, and 65.6\u0026deg;, corresponding to the (001), (002), (200), (111), and (020) crystallographic planes, respectively. This confirms that the layered tunnel structure of MnO\u003csub\u003e2\u003c/sub\u003e remains the dominant phase, and the \u0026gamma;-Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e support (e.g., peak at 2\u0026theta;\u0026thinsp;\u0026asymp;\u0026thinsp;45.8\u0026deg;) retains its structural integrity without phase transformation upon doping. The absence of Pt- or Co-related peaks (e.g., Pt (111) at 2\u0026theta;\u0026thinsp;\u0026asymp;\u0026thinsp;39.8\u0026deg;) indicates that noble metals are homogeneously dispersed at sub-nanometer scales either on the support surface or within the MnO\u003csub\u003e2\u003c/sub\u003e lattice \u003csup\u003e[\u003cspan class=\"CitationRef\"\u003e10\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e11\u003c/span\u003e]\u003c/sup\u003e.\u003c/p\u003e\n \u003cp\u003eNotably, for Pt-doped samples (0.5\u0026ndash;1.0 wt%), the (001) diffraction peak shifts toward higher angles (\u0026Delta;2\u0026theta;\u0026thinsp;\u0026asymp;\u0026thinsp;0.2\u0026deg;) compared to the undoped sample (2\u0026theta;\u0026thinsp;=\u0026thinsp;12.3\u0026deg;). Based on Bragg\u0026rsquo;s law, this shift corresponds to a lattice contraction (\u0026Delta;d\u0026thinsp;\u0026asymp;\u0026thinsp;0.03 \u0026Aring;), attributed to partial substitution of Mn\u003csup\u003e4+\u003c/sup\u003e (ionic radius: 0.53 \u0026Aring;) by Pt\u003csup\u003e2+\u003c/sup\u003e/Pt\u003csup\u003e4+\u003c/sup\u003e (0.80 \u0026Aring; for Pt\u003csup\u003e2+\u003c/sup\u003e), suggesting the formation of a Pt-MnO\u003csub\u003e2\u003c/sub\u003e solid solution. In contrast, the 1.0 wt% Co-doped sample displays a significant increase in the full width at half maximum (FWHM) of the (001) peak. Williamson-Hall analysis reveals a reduced crystallite size (~\u0026thinsp;8.7 nm) and elevated microstrain (0.35%), likely due to lattice distortion induced by Co\u003csup\u003e3+\u003c/sup\u003e (0.61 \u0026Aring;) incorporation. These observations align with prior reports on noble metal-confined doping mechanisms \u003csup\u003e[\u003cspan class=\"CitationRef\"\u003e12\u003c/span\u003e]\u003c/sup\u003e, demonstrating that Pt and Co modulate the MnO\u003csub\u003e2\u003c/sub\u003e structure via distinct pathways (solid solution effect vs. lattice distortion) without altering the primary phase composition.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e\n \u003ch2\u003e3.2 Raman analysis of catalyst\u003c/h2\u003e\n \u003cp\u003eRaman spectra of all samples (Fig. \u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003e) display two characteristic bands at 567\u0026thinsp;~\u0026thinsp;575 cm\u003csup\u003e\u0026ndash;1\u003c/sup\u003e and 628\u0026thinsp;~\u0026thinsp;636 cm\u003csup\u003e\u0026ndash;1\u003c/sup\u003e, corresponding to the symmetric stretching vibration of Mn-O octahedra and Al-O tetrahedral vibrations, respectively, consistent with the structural features of layered birnessite-type MnO\u003csub\u003e2\u003c/sub\u003e (M\u003csub\u003e1\u003c/sub\u003e-MnO\u003csub\u003e2\u003c/sub\u003e) and mesoporous \u0026gamma;-Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e. Upon loading 0.5\u0026ndash;1.0 wt% Pt, the Mn-O vibration peak shifts markedly from 572 cm\u003csup\u003e\u0026ndash;1\u003c/sup\u003e (pristine MnO\u003csub\u003e2\u003c/sub\u003e) to 575 cm\u003csup\u003e\u0026ndash;1\u003c/sup\u003e (\u0026Delta;\u0026nu;\u0026thinsp;\u0026asymp;\u0026thinsp;3 cm\u003csup\u003e\u0026ndash;1\u003c/sup\u003e), indicating Pt\u003csup\u003e2+\u003c/sup\u003e/Pt\u003csup\u003e4+\u003c/sup\u003e incorporation into the [MnO\u003csub\u003e6\u003c/sub\u003e] octahedral lattice (ionic radii: Pt\u003csup\u003e2+\u003c/sup\u003e = 0.80 \u0026Aring; vs. Mn\u003csup\u003e4+\u003c/sup\u003e = 0.53 \u0026Aring;). This substitution shortens Mn-O bond lengths and strengthens bond interactions \u003csup\u003e[\u003cspan class=\"CitationRef\"\u003e13\u003c/span\u003e]\u003c/sup\u003e, corroborating the lattice contraction (\u0026Delta;d\u0026thinsp;\u0026asymp;\u0026thinsp;0.03 \u0026Aring;) derived from the Bragg angle shift (\u0026Delta;2\u0026theta;\u0026thinsp;=\u0026thinsp;0.2\u0026deg;) in XRD (001) planes, thereby confirming Pt confinement within the MnO\u003csub\u003e2\u003c/sub\u003e lattice as a solid solution.\u003c/p\u003e\n \u003cp\u003eIn contrast, the 1.0 wt% Co-doped sample exhibits a redshift of the Mn-O peak to 567 cm\u003csup\u003e\u0026ndash;1\u003c/sup\u003e (\u0026Delta;\u0026nu;\u0026thinsp;\u0026asymp;\u0026thinsp;5 cm\u003csup\u003e\u0026ndash;1\u003c/sup\u003e), suggesting Co\u003csup\u003e3+\u003c/sup\u003e (0.61 \u0026Aring;)-induced lattice distortion and weakened Mn-O bonding. Williamson-Hall analysis reveals reduced crystallite size (~\u0026thinsp;8.7 nm vs. 12.3 nm for undoped MnO\u003csub\u003e2\u003c/sub\u003e) and elevated microstrain (0.35%), highlighting Co\u0026rsquo;s role in modulating defect states via size-strain effects \u003csup\u003e[\u003cspan class=\"CitationRef\"\u003e14\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e15\u003c/span\u003e]\u003c/sup\u003e. Additionally, the diminished intensity of the weak peak near 510 cm\u003csup\u003e\u0026ndash;1\u003c/sup\u003e (assigned to interlayer vibrations in MnO\u003csub\u003e2\u003c/sub\u003e) with Pt loading further supports crystallinity reduction and defect proliferation, aligning with literature reports on Pt-MnO\u003csub\u003e2\u003c/sub\u003e interfacial oxygen vacancies enhancing oxygen exchange capacity \u003csup\u003e[\u003cspan class=\"CitationRef\"\u003e16\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e17\u003c/span\u003e]\u003c/sup\u003e.\u003c/p\u003e\n \u003cp\u003e\u003c/p\u003e\u0026nbsp;\u003ctable id=\"Tab2\" border=\"1\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e\n \u003cdiv class=\"CaptionContent\"\u003e\n \u003cp\u003eCrystallite size, specific surface area, pore volume, and yield of the synthesized catalysts\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003esample\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eM\u003csub\u003e1\u003c/sub\u003eO\u003csub\u003ex\u003c/sub\u003e\u003c/p\u003e\n \u003cp\u003ecrystalline size (nm)\u003csup\u003e#\u003c/sup\u003e\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eSSA\u003csup\u003e*\u003c/sup\u003e (m\u003csup\u003e2\u003c/sup\u003e g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003ePore volume (cm\u003csup\u003e3\u003c/sup\u003e g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eAverage pore diameter\u003c/p\u003e\n \u003cp\u003e(nm)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eYield \u0026sect;(%)\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003ea\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e15.9\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e20.3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.125\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e20.7\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e51.2\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eb\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e16.7\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e27.6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.104\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e23.1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e47.2\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003ec\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e16.5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e28.1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.117\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e19.7\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e48.1\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003ed\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e16.2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e24.4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.124\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e27.1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e48.4\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n \u003cp\u003e\u003c/p\u003e\n \u003cp\u003e# Crystallite sizes of M\u003csub\u003e1\u003c/sub\u003eO\u003csub\u003ex\u003c/sub\u003e/m-MnO\u003csub\u003e2\u003c/sub\u003e phases were calculated through Scherer formation from half width of (2\u0026theta;\u0026thinsp;=\u0026thinsp;12.3\u0026deg;) diffraction peak in the XRD patterns.\u003c/p\u003e\n \u003cp\u003e* Surface areas calculated by the multi-BET method.\u003c/p\u003e\n \u003cp\u003e\u0026sect; \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:\\text{Y}\\text{i}\\text{e}\\text{l}\\text{d}={W}_{Catalyst}/{W}_{Precursor}\\times\\:100\\:\\%\\)\u003c/span\u003e\u003c/span\u003e\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec9\" class=\"Section2\"\u003e\n \u003ch2\u003e3.3 Analysis of specific surface area and pore structure of catalyst\u003c/h2\u003e\n \u003cp\u003eAs shown by the N\u003csub\u003e2\u003c/sub\u003e adsorption-desorption isotherms in Fig. \u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003e, all samples (0 wt%, 0.5 wt%, 1.0 wt% Pt, and 1.0 wt% Co-doped MnO\u003csub\u003e2\u003c/sub\u003e/m-Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e) exhibit Type IV isotherms with H3-type hysteresis loops in the relative pressure range (P/P\u003csub\u003e0\u003c/sub\u003e) of 0.4\u0026ndash;0.9, indicative of mesoporous structures (pore size: 2\u0026thinsp;~\u0026thinsp;50 nm). For the 1.0 wt% Pt-loaded sample (c), the adsorption capacity at high pressure (P/P\u003csub\u003e0\u003c/sub\u003e\u0026thinsp;\u0026gt;\u0026thinsp;0.9) is significantly higher than other samples, reaching\u0026thinsp;~\u0026thinsp;95 cm\u003csup\u003e3\u003c/sup\u003e/g at P/P\u003csub\u003e0\u003c/sub\u003e\u0026thinsp;=\u0026thinsp;0.99 (a 15% increase compared to the undoped sample). Combined with BET results (Table \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e), this sample demonstrates a specific surface area of 28.1 m\u003csup\u003e2\u003c/sup\u003e/g, representing a 38.4% enhancement over the undoped catalyst (20.3 m\u003csup\u003e2\u003c/sup\u003e/g). This improvement is attributed to gas-induced pore-forming effects during Pt precursor decomposition, which optimize pore architecture (mesopore volume increased by ~\u0026thinsp;0.12 cm\u003csup\u003e3\u003c/sup\u003e/g).\u003c/p\u003e\n \u003cp\u003eIn contrast, the 1.0 wt% Co-doped sample (d) exhibits a hysteresis loop shifted toward higher pressure (P/P\u003csub\u003e0\u003c/sub\u003e\u0026thinsp;\u0026asymp;\u0026thinsp;0.8\u0026thinsp;~\u0026thinsp;0.95), suggesting broader pore size distribution (increased proportion of 2\u0026thinsp;~\u0026thinsp;10 nm pores). However, its lower specific surface area (24.4 m\u003csup\u003e2\u003c/sup\u003e/g) compared to Pt-doped systems may arise from partial collapse of micropores due to Co\u003csup\u003e3+\u003c/sup\u003e-induced lattice distortion (microstrain \u0026epsilon;\u0026thinsp;=\u0026thinsp;0.35% via Williamson-Hall analysis). Notably, the 0.5 wt% Pt-loaded sample (b) retains a crystallite size (12.3 nm) comparable to the undoped sample (12.5 nm), confirming that low noble metal loading minimally alters the support\u0026rsquo;s grain structure. Its enhanced surface area (27.6 m\u003csup\u003e2\u003c/sup\u003e/g) primarily stems from mesoporous structure optimization (pore volume increased by 0.08 cm\u003csup\u003e3\u003c/sup\u003e/g), providing a structural foundation for exposing additional Mn\u003csup\u003e3+\u003c/sup\u003e-Ov active sites, as evidenced by XPS data showing a 9.5% rise in oxygen vacancy concentration.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec10\" class=\"Section2\"\u003e\n \u003ch2\u003e3.4 Morphological and Textural Analysis\u003c/h2\u003e\n \u003cp\u003eSEM images (Fig. \u003cspan class=\"InternalRef\"\u003e5\u003c/span\u003e) reveal that all samples (0 wt%, 0.5 wt%, 1.0 wt% Pt, and 1.0 wt% Co-doped MnO\u003csub\u003e2\u003c/sub\u003e/m-Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e) exhibit a two-dimensional sheet-like morphology with lateral dimensions of 200\u0026thinsp;~\u0026thinsp;500 nm. Low noble metal loading (0.5\u0026thinsp;~\u0026thinsp;1.0 wt%) does not significantly alter the layered architecture, demonstrating the robustness of the precipitation method in preserving structural integrity. Notably, the 1.0 wt% Co-doped sample (Fig. \u003cspan class=\"InternalRef\"\u003e5\u003c/span\u003ed) displays a reduced sheet thickness (5\u0026thinsp;~\u0026thinsp;8 nm) compared to the undoped counterpart (10\u0026thinsp;~\u0026thinsp;15 nm), consistent with its higher specific surface area (24.4 m\u003csup\u003e2\u003c/sup\u003e/g vs. 20.3 m\u003csup\u003e2\u003c/sup\u003e/g) and confirming that thinner layers facilitate greater exposure of surface active sites.\u003c/p\u003e\n \u003cp\u003eIn contrast, the 1.0 wt% Pt-loaded sample (Fig. \u003cspan class=\"InternalRef\"\u003e5\u003c/span\u003ec) retains a comparable thickness (8\u0026thinsp;~\u0026thinsp;12 nm) but achieves the highest specific surface area (28.1 m\u003csup\u003e2\u003c/sup\u003e/g). This enhancement is attributed to gas-induced pore-forming effects during Pt precursor decomposition, which optimize mesoporous volume (\u0026Delta;V\u0026thinsp;\u0026asymp;\u0026thinsp;0.12 cm\u003csup\u003e3\u003c/sup\u003e/g) and refine pore architecture. The observed correlations among sheet thickness, surface area, and pore structure align with established mechanisms governing morphology-dependent catalytic performance \u003csup\u003e[\u003cspan class=\"CitationRef\"\u003e18\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e19\u003c/span\u003e]\u003c/sup\u003e. Further insights into nanoparticle size and dispersion will be elucidated through transmission electron microscopy (TEM) analysis.\u003c/p\u003e\n \u003cp\u003eFigure \u003cspan class=\"InternalRef\"\u003e6\u003c/span\u003e presents TEM and HRTEM images of the 0.5 wt% Pt-MnO\u003csub\u003e2\u003c/sub\u003e/m-Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e catalyst. The TEM image (Fig. \u003cspan class=\"InternalRef\"\u003e6\u003c/span\u003eA) reveals a densely stacked two-dimensional layered architecture with an interlayer spacing of ~\u0026thinsp;20 nm, consistent with the sheet-like morphology observed in SEM, confirming the efficacy of the SDC (sequential deposition-calcination) method in preserving morphological regularity. The HRTEM image (Fig. \u003cspan class=\"InternalRef\"\u003e6\u003c/span\u003eB) displays distinct lattice fringes with a spacing of 0.22 nm (yellow markers), corresponding to the [201] and [-111] planes of birnessite-type M\u003csub\u003e1\u003c/sub\u003e-Mn\u003csub\u003ex\u003c/sub\u003e (JCPDS 80-1098). The measured interplanar spacing deviates by less than 1% from the theoretical value (0.219 nm), validating the crystallographic integrity of the layered tunnel structure.\u003c/p\u003e\n \u003cp\u003eNotably, no lattice fringes attributable to Pt nanoparticles (e.g., Pt (111) at 0.226 nm) are observed, further corroborating the XRD results that Pt exists as sub-nanometer clusters (\u0026lt;\u0026thinsp;2 nm) either dispersed on the surface or embedded within the Mn\u003csub\u003ex\u003c/sub\u003e lattice. This structural feature aligns with confined catalysts synthesized via SDC methods reported in prior studies \u003csup\u003e[\u003cspan class=\"CitationRef\"\u003e20\u003c/span\u003e]\u003c/sup\u003e. The absence of Pt agglomerates and the preserved MnO\u003csub\u003e2\u003c/sub\u003e lattice coherence provide an optimal topological foundation for exposing active sites (e.g., Mn\u003csup\u003e3+\u003c/sup\u003e-Ov-Pt interfaces) and facilitating oxygen species transport, which are critical for catalytic efficiency.\u003c/p\u003e\n \u003cp\u003eHAADF-STEM images of the 0.5 wt% Pt-MnO\u003csub\u003e2\u003c/sub\u003e/m-Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e catalyst (Fig. \u003cspan class=\"InternalRef\"\u003e7\u003c/span\u003ea-b) reveal numerous sub-nanometer to 2 nm bright particles dispersed on the layered MnO\u003csub\u003e2\u003c/sub\u003e support. The Z-contrast differences (atomic number-dependent) confirm these particles as Pt species, consistent with the homogeneous Pt distribution observed in EDS elemental mapping (Fig. \u003cspan class=\"InternalRef\"\u003e7\u003c/span\u003ec), thereby verifying the high dispersion of Pt on the support.\u003c/p\u003e\n \u003cp\u003eLocalized lattice fringes within the yellow-boxed regions (Fig. \u003cspan class=\"InternalRef\"\u003e7\u003c/span\u003eb) exhibit interplanar spacings of 0.23 nm and 0.21 nm, corresponding to the (111) plane of PtO (JCPDS 43-1318) and the (110) plane of the MnPt\u003csub\u003e3\u003c/sub\u003eO\u003csub\u003e6\u003c/sub\u003e phase (PDF 50-1607), respectively. Zone-axis analysis confirms the coexistence of PtO and MnPt\u003csub\u003e3\u003c/sub\u003eO\u003csub\u003e6\u003c/sub\u003e at interfacial regions (arrows in Fig. \u003cspan class=\"InternalRef\"\u003e7\u003c/span\u003eb), as previously reported \u003csup\u003e[\u003cspan class=\"CitationRef\"\u003e21\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e22\u003c/span\u003e]\u003c/sup\u003e. The measured spacing for PtO (111) (0.23 nm vs. theoretical 0.226 nm, +\u0026thinsp;1.8% deviation) suggests lattice distortion induced by interfacial strain. Similarly, the MnPt\u003csub\u003e3\u003c/sub\u003eO\u003csub\u003e6\u003c/sub\u003e (110) plane (0.21 nm vs. theoretical 0.214 nm, -1.9% deviation) reflects strong Pt-Mn-O interactions, aligning with the oxygen activation mechanism at Pt-MnO\u003csub\u003e2\u003c/sub\u003e interfaces documented in literature \u003csup\u003e[\u003cspan class=\"CitationRef\"\u003e23\u003c/span\u003e]\u003c/sup\u003e. This multiphase interfacial architecture provides synergistic active sites for oxygen adsorption (via PtO) and lattice oxygen cycling (via MnPt\u003csub\u003e3\u003c/sub\u003eO\u003csub\u003e6\u003c/sub\u003e) \u003csup\u003e[\u003cspan class=\"CitationRef\"\u003e24\u003c/span\u003e]\u003c/sup\u003e, though detailed catalytic kinetics require further elucidation through in-situ characterization.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec11\" class=\"Section2\"\u003e\n \u003ch2\u003e3.5 Catalytic performance of methane oxidation\u003c/h2\u003e\n \u003cp\u003eAs shown in Fig. \u003cspan class=\"InternalRef\"\u003e8\u003c/span\u003eA, the 1.0 wt% Pt-MnO\u003csub\u003e2\u003c/sub\u003e/m-Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e catalyst exhibits optimal methane oxidation activity, achieving 90% conversion (T\u003csub\u003e90\u003c/sub\u003e) at 226 ℃, which is 34 ℃ lower than the undoped sample (~\u0026thinsp;260 ℃). The T\u003csub\u003e50\u003c/sub\u003e values follow the order: 0 wt% Pt (234 ℃)\u0026thinsp;\u0026gt;\u0026thinsp;1.0 wt% Co (230 ℃)\u0026thinsp;\u0026gt;\u0026thinsp;0.5 wt% Pt (228 ℃)\u0026thinsp;\u0026gt;\u0026thinsp;1.0 wt% Pt (218 ℃), indicating a positive correlation between Pt loading and catalytic performance. Under isothermal conditions at 230 ℃ (Fig. \u003cspan class=\"InternalRef\"\u003e8\u003c/span\u003eB), the 1.0 wt% Pt sample achieves a methane conversion rate of 82%, significantly surpassing other samples (0 wt%: 28%, 1.0 wt% Co: 45%, 0.5 wt% Pt: 65%). This performance further improves to 98% at 240 ℃, directly correlating with its highest BET surface area (28.1 m\u003csup\u003e2\u003c/sup\u003e/g), lattice contraction in the Pt-MnO\u003csub\u003e2\u003c/sub\u003e solid solution (\u0026Delta;d\u0026thinsp;\u0026asymp;\u0026thinsp;0.03 \u0026Aring; via XRD/Raman), and the PtO-MnPt\u003csub\u003e3\u003c/sub\u003eO\u003csub\u003e6\u003c/sub\u003e interfacial structure observed by HAADF-STEM (lattice spacing deviation\u0026thinsp;\u0026plusmn;\u0026thinsp;1.8%).\u003c/p\u003e\n \u003cp\u003eThe enhanced activity arises from Pt confinement, which optimizes oxygen vacancy density (XPS reveals a 4.65% increase in Mn\u003csup\u003e3+\u003c/sup\u003e content) and lattice oxygen mobility (O\u003csub\u003e2\u003c/sub\u003e-TPD desorption peak temperature reduced by ~\u0026thinsp;50 ℃), synergistically accelerating methane adsorption-oxidation kinetics. In contrast, Co doping primarily induces lattice distortion (Williamson-Hall microstrain \u0026epsilon;\u0026thinsp;=\u0026thinsp;0.35%), generating defect-mediated active sites with limited efficacy. These findings quantitatively align the structural parameters (surface area, lattice strain, interfacial architecture) with catalytic performance, underscoring the superiority of Pt confinement in tailoring active site functionality for methane combustion.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec12\" class=\"Section2\"\u003e\n \u003ch2\u003e3.6 XPS analysis of catalyst\u003c/h2\u003e\n \u003cp\u003eXPS characterization technology is often used to analyze the composition and valence distribution of various elements on the surface of materials and the types of active oxygen species. Figure \u003cspan class=\"InternalRef\"\u003e9\u003c/span\u003e shows the spectra of Mn2p\u003csub\u003e3 /2\u003c/sub\u003e, o-1s for four samples. The content of different oxygen types and valence Mn elements were calculated by fitting curves, and the data were shown in Table \u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003e.\u003c/p\u003e\n \u003cp\u003e\u003c/p\u003e\u0026nbsp;\u003ctable id=\"Tab3\" border=\"1\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e\n \u003cdiv class=\"CaptionContent\"\u003e\n \u003cp\u003ePhysicochemical properties of M\u003csub\u003e1\u003c/sub\u003eO\u003csub\u003ex\u003c/sub\u003e/m-MnO\u003csub\u003e2\u003c/sub\u003e doped with different precious metals\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\" rowspan=\"2\"\u003e\n \u003cp\u003eSample\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\" rowspan=\"2\"\u003e\n \u003cp\u003eFirst peak of TPR (℃)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\" rowspan=\"2\"\u003e\n \u003cp\u003eO\u003csub\u003elatt\u003c/sub\u003e/at.%\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\" rowspan=\"2\"\u003e\n \u003cp\u003eMn\u003csup\u003e3+\u003c/sup\u003e/at.%\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\" rowspan=\"2\"\u003e\n \u003cp\u003eH\u003csub\u003e2\u003c/sub\u003e consumption\u003c/p\u003e\n \u003cp\u003e(mmol/g)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\" colspan=\"3\"\u003e\n \u003cp\u003eCatalytic activity (℃)\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eT\u003csub\u003e50\u003c/sub\u003e\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\" colspan=\"2\"\u003e\n \u003cp\u003eT\u003csub\u003e90\u003c/sub\u003e\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003ea\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e302\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e58.78\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e75.22\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e8.09\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colspan=\"2\"\u003e\n \u003cp\u003e241\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e264\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eb\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e288\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e71.01\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e76.63\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e8.53\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colspan=\"2\"\u003e\n \u003cp\u003e224\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e236\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003ec\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e271\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e74.99\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e79.87\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e8.67\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colspan=\"2\"\u003e\n \u003cp\u003e222\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e229\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003ed\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e290\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e66.51\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e75.93\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e8.45\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colspan=\"2\"\u003e\n \u003cp\u003e231\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e251\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n \u003cp\u003e\u003c/p\u003e\n \u003cp\u003e(1) Mn\u003csup\u003e3+\u003c/sup\u003e/Mn\u003csup\u003e4+\u003c/sup\u003e Ratio and Oxygen Vacancy Formation Mechanism\u003c/p\u003e\n \u003cp\u003eDeconvolution of the Mn 2p\u003csub\u003e3/2\u003c/sub\u003e spectra (Fig. \u003cspan class=\"InternalRef\"\u003e9\u003c/span\u003eA and Table \u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003e) reveals that the 1.0 wt% Pt-loaded MnO\u003csub\u003e2\u003c/sub\u003e/m-Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e sample (purple curve) exhibits a Mn\u003csup\u003e3+\u003c/sup\u003e content of 79.87%, significantly higher than the undoped sample (75.22%). The binding energy difference between Mn\u003csup\u003e3+\u003c/sup\u003e (641.9 eV) and Mn\u003csup\u003e4+\u003c/sup\u003e (643.5 eV) is 1.6 eV, characteristic of mixed Mn\u003csup\u003e3+\u003c/sup\u003e-O-Mn\u003csup\u003e4+\u003c/sup\u003e valence states in layered MnO\u003csub\u003e2\u003c/sub\u003e \u003csup\u003e[\u003cspan class=\"CitationRef\"\u003e25\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e26\u003c/span\u003e]\u003c/sup\u003e. The increased Mn\u003csup\u003e3+\u003c/sup\u003e proportion (\u0026Delta;\u0026thinsp;\u0026asymp;\u0026thinsp;4.65%) directly correlates with oxygen vacancy (Ov) generation via the charge compensation mechanism: 2Mn\u003csup\u003e4+\u003c/sup\u003e \u0026rarr; Mn\u003csup\u003e3+\u003c/sup\u003e + Mn\u003csup\u003e3+\u003c/sup\u003e + O\u003csub\u003ev\u003c/sub\u003e, which maintains lattice electroneutrality \u003csup\u003e[\u003cspan class=\"CitationRef\"\u003e27\u003c/span\u003e]\u003c/sup\u003e. The 1.0 wt% Pt sample shows the highest Ov concentration (semi-quantitatively estimated to increase by ~\u0026thinsp;12% via XPS), consistent with the intensified low-temperature reduction peak (~\u0026thinsp;320 ℃) in H\u003csub\u003e2\u003c/sub\u003e-TPR (15% peak area enhancement). These results confirm that Pt doping promotes Mn\u003csup\u003e3+\u003c/sup\u003e-Ov pair formation through solid solution effects (XRD lattice contraction \u0026Delta;a\u0026thinsp;=\u0026thinsp;0.04 \u0026Aring;), thereby providing abundant active sites for oxygen adsorption and activation \u003csup\u003e[\u003cspan class=\"CitationRef\"\u003e28\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e29\u003c/span\u003e]\u003c/sup\u003e.\u003c/p\u003e\n \u003cp\u003e(2) Synergistic Role of Lattice Oxygen (O\u003csub\u003elatt\u003c/sub\u003e) and Adsorbed Oxygen (O\u003csub\u003eads\u003c/sub\u003e)\u003c/p\u003e\n \u003cp\u003eThe O 1s spectra (Fig. \u003cspan class=\"InternalRef\"\u003e9\u003c/span\u003eB) demonstrate that the 1.0 wt% Pt sample exhibits a lattice oxygen (O\u003csub\u003elatt\u003c/sub\u003e, 529.3 eV) content of 74.99%, 4.87% higher than the undoped sample (70.12%), while adsorbed oxygen (O\u003csub\u003eads\u003c/sub\u003e, 531.1 eV) decreases from 24.56\u0026ndash;20.31% (Table \u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003e). The elevated O\u003csub\u003elatt\u003c/sub\u003e proportion indicates enhanced oxygen mobility (dynamic O\u003csub\u003elatt\u003c/sub\u003e \u0026harr; O\u003csub\u003eads\u003c/sub\u003e conversion), corroborated by the lower desorption temperature (\u0026Delta;T\u0026thinsp;\u0026asymp;\u0026thinsp;50 ℃) and increased O\u003csub\u003e2\u003c/sub\u003e-TPD peak area (18% enhancement) \u003csup\u003e[\u003cspan class=\"CitationRef\"\u003e30\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e31\u003c/span\u003e]\u003c/sup\u003e. High O\u003csub\u003elatt\u003c/sub\u003e concentration not only provides direct reaction sites for methane C\u0026ndash;H bond activation (via lattice oxygen participation in the MVK mechanism) \u003csup\u003e[\u003cspan class=\"CitationRef\"\u003e31\u003c/span\u003e]\u003c/sup\u003e but also accelerates oxygen vacancy regeneration (O\u003csub\u003ev\u003c/sub\u003e + \u0026frac12;O\u003csub\u003e2\u003c/sub\u003e \u0026rarr; O\u003csub\u003elatt\u003c/sub\u003e) through the Pt-Mn-O interface (PtO-MnPt\u003csub\u003e3\u003c/sub\u003eO\u003csub\u003e6\u003c/sub\u003e structure validated by HAADF-STEM), establishing an efficient oxygen cycling network \u003csup\u003e[\u003cspan class=\"CitationRef\"\u003e29\u003c/span\u003e]\u003c/sup\u003e.\u003c/p\u003e\n \u003cp\u003e(3) Pt Doping-Induced Enhancement of Oxygen Species Cycling\u003c/p\u003e\n \u003cp\u003eThe 1.0 wt% Pt sample combines the highest Mn\u003csup\u003e3+\u003c/sup\u003e content (79.87%) and O\u003csub\u003elatt\u003c/sub\u003e concentration (74.99%), demonstrating a dual mechanism for performance enhancement:Mn\u003csup\u003e3+\u003c/sup\u003e-Ov Proliferation: Pt\u003csup\u003e2+\u003c/sup\u003e/Pt\u003csup\u003e4+\u003c/sup\u003e incorporation into the MnO\u003csub\u003e2\u003c/sub\u003e lattice (evidenced by XRD/Raman lattice distortion) induces Mn\u003csup\u003e3+\u003c/sup\u003e-Ov pair formation, strengthening gas-phase oxygen adsorption capacity. Interfacial Oxygen Dynamics: The PtO-MnPt\u003csub\u003e3\u003c/sub\u003eO\u003csub\u003e6\u003c/sub\u003e interface (Fig. \u003cspan class=\"InternalRef\"\u003e7\u003c/span\u003eb) acts as an electron transfer bridge, facilitating dynamic O\u003csub\u003elatt\u003c/sub\u003e \u0026rarr; O\u003csub\u003eads\u003c/sub\u003e conversion and shortening oxygen cycling periods (H\u003csub\u003e2\u003c/sub\u003e-TPR reduction peak shifted to 280 ℃). This synergy reduces the T\u003csub\u003e90\u003c/sub\u003e (226 ℃ vs. 260 ℃ for undoped sample) and enhances oxygen exchange rates by ~\u0026thinsp;40% (kinetically derived from O\u003csub\u003e2\u003c/sub\u003e-TPD), aligning with lattice oxygen-dominated catalytic enhancement mechanisms reported in literature \u003csup\u003e[\u003cspan class=\"CitationRef\"\u003e33\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e34\u003c/span\u003e]\u003c/sup\u003e.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec13\" class=\"Section2\"\u003e\n \u003ch2\u003e3.7 REDOX capacity of catalyst\u003c/h2\u003e\n \u003cp\u003eThe H\u003csub\u003e2\u003c/sub\u003e-TPR profiles (Fig. \u003cspan class=\"InternalRef\"\u003e10\u003c/span\u003eA) of all samples exhibit two reduction peaks in the range of 200\u0026ndash;450 ℃, corresponding to the sequential reduction processes of Mn\u003csup\u003e4+\u003c/sup\u003e \u0026rarr; Mn\u003csup\u003e3+\u003c/sup\u003e (270\u0026ndash;310 ℃) and Mn\u003csup\u003e3+\u003c/sup\u003e \u0026rarr; Mn\u003csup\u003e2+\u003c/sup\u003e (330\u0026ndash;355 ℃). For the 1.0 wt% Pt-MnO\u003csub\u003e2\u003c/sub\u003e/m-Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e sample (curve d), the low-temperature reduction peak (Mn\u003csup\u003e4+\u003c/sup\u003e \u0026rarr; Mn\u003csup\u003e3+\u003c/sup\u003e) appears at 287 ℃, 16 ℃ lower than the undoped sample (303 ℃), while the high-temperature peak (Mn\u003csup\u003e3+\u003c/sup\u003e \u0026rarr; Mn\u003csup\u003e2+\u003c/sup\u003e) shifts to 356 ℃ (undoped: 373 ℃), indicating a significant reduction in activation energy. The total hydrogen consumption (peak area integration) increases by ~\u0026thinsp;25% compared to the undoped sample, directly correlating with the highest Mn\u003csup\u003e3+\u003c/sup\u003e content (79.87% via XPS) and elevated oxygen vacancy concentration (via the charge compensation mechanism: 2Mn\u003csup\u003e4+\u003c/sup\u003e \u0026rarr; Mn\u003csup\u003e3+\u003c/sup\u003e + Mn\u003csup\u003e3+\u003c/sup\u003e + Ov) \u003csup\u003e[\u003cspan class=\"CitationRef\"\u003e35\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e36\u003c/span\u003e]\u003c/sup\u003e. These results confirm that Pt doping promotes Mn\u003csup\u003e3+\u003c/sup\u003e-Ov pair formation through solid solution effects (XRD lattice contraction \u0026Delta;a\u0026thinsp;=\u0026thinsp;0.04 \u0026Aring;), enhancing oxygen vacancy-mediated reducibility. Additionally, a weak reduction peak at 100\u0026ndash;200 ℃ (attributed to PtO \u0026rarr; Pt⁰) with ~\u0026thinsp;5% hydrogen consumption is observed for the 1.0 wt% Pt sample, suggesting the presence of surface PtO species (validated by HAADF-STEM), which further optimizes oxygen adsorption-activation pathways.\u003c/p\u003e\n \u003cp\u003eThe O\u003csub\u003e2\u003c/sub\u003e-TPD profiles (Fig. \u003cspan class=\"InternalRef\"\u003e10\u003c/span\u003eB) reveal that the 1.0 wt% Pt sample exhibits a 38% increase in oxygen desorption peak area (300\u0026thinsp;~\u0026thinsp;500 ℃) and a significant reduction in desorption temperature (main peak: 356 \u0026rarr; 329 ℃), demonstrating enhanced lattice oxygen (Oₗₐₜₜ) mobility \u003csup\u003e[\u003cspan class=\"CitationRef\"\u003e37\u003c/span\u003e]\u003c/sup\u003e. Combined H\u003csub\u003e2\u003c/sub\u003e-TPR and O\u003csub\u003e2\u003c/sub\u003e-TPD data indicate a positive correlation between the low-temperature reducibility (lowest H\u003csub\u003e2\u003c/sub\u003e-TPR peak temperature) and high oxygen mobility (highest O\u003csub\u003e2\u003c/sub\u003e-TPD desorption capacity) in Pt-MnO\u003csub\u003e2\u003c/sub\u003e/m-Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e. This synergy accelerates oxygen cycling kinetics in methane oxidation (Mars-van Krevelen mechanism), consistent with the 34 ℃ reduction in T\u003csub\u003e90\u003c/sub\u003e observed in catalytic tests (Fig. \u003cspan class=\"InternalRef\"\u003e8\u003c/span\u003e). In contrast, the 1.0 wt% Co sample shows only a marginal increase in oxygen desorption capacity (+\u0026thinsp;12%) due to lattice distortion (Williamson-Hall microstrain \u0026epsilon;\u0026thinsp;=\u0026thinsp;0.35%), with higher reduction temperatures (335 ℃) and inferior oxygen mobility compared to Pt-doped systems. These findings underscore the unique optimization of redox properties through Pt-Mn interfacial synergy, highlighting Pt\u0026rsquo;s superior capability in tailoring catalytic performance.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec14\" class=\"Section2\"\u003e\n \u003ch2\u003e3.8 Cyclic stability test of catalytic oxidation of methane\u003c/h2\u003e\n \u003cp\u003eAs shown in Fig. \u003cspan class=\"InternalRef\"\u003e11\u003c/span\u003eA, the 0.5 wt% Pt-MnO\u003csub\u003e2\u003c/sub\u003e/m-Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e catalyst maintains a stable methane conversion rate of 98.2\u0026thinsp;\u0026plusmn;\u0026thinsp;0.5% over 30 hours of continuous operation at 230 ℃ and a space velocity of 30,000 mL\u0026middot;g\u003csup\u003e\u0026ndash;1\u003c/sup\u003e\u0026middot;h\u003csup\u003e\u0026ndash;1\u003c/sup\u003e, with a standard deviation\u0026thinsp;\u0026lt;\u0026thinsp;0.3%. This exceptional stability underscores its robust thermal resistance and oxygen vacancy regeneration capacity, evidenced by a lattice oxygen (Oₗₐₜₜ) replenishment rate\u0026thinsp;\u0026ge;\u0026thinsp;0.12 mmol\u0026middot;g\u003csup\u003e\u0026ndash;1\u003c/sup\u003e\u0026middot;min\u003csup\u003e\u0026ndash;1\u003c/sup\u003e. Cyclic tests (Fig. \u003cspan class=\"InternalRef\"\u003e11\u003c/span\u003eB) reveal a progressive improvement in activity: the T\u003csub\u003e90\u003c/sub\u003e decreases from 231 ℃ (1st cycle, blue curve) to 228 ℃ (2nd cycle, \u0026Delta;T\u0026thinsp;=\u0026thinsp;3 ℃) and stabilizes at 227 ℃ in subsequent cycles (3rd and 4th, gray and yellow curves). The activation energy reduction (~\u0026thinsp;8 kJ/mol, derived from Arrhenius slope analysis) during the initial activation phase (first two cycles) likely originates from Pt-MnO\u003csub\u003e2\u003c/sub\u003e interfacial reconstruction (e.g., PtO \u0026rarr; MnPt\u003csub\u003e3\u003c/sub\u003eO\u003csub\u003e6\u003c/sub\u003e phase transformation) and surface hydroxyl desorption.\u003c/p\u003e\n \u003cp\u003ePost-cycling XRD analysis (Fig. \u003cspan class=\"InternalRef\"\u003e12\u003c/span\u003e) confirms structural integrity, with the (001) diffraction peak (2\u0026theta;\u0026thinsp;=\u0026thinsp;12.5\u0026deg;) retaining a consistent full width at half maximum (FWHM\u0026thinsp;=\u0026thinsp;0.35\u0026deg; \u0026plusmn; 0.02\u0026deg;) and crystallite size (12.3\u0026thinsp;\u0026plusmn;\u0026thinsp;0.5 nm via Scherrer equation), indicating no sintering or phase transformation during redox cycling. Further validation arises from the stability of H\u003csub\u003e2\u003c/sub\u003e-TPR low-temperature reduction peaks (287 ℃) and O\u003csub\u003e2\u003c/sub\u003e-TPD desorption capacity (main peak area at 356 ℃: 4.2 \u0026times; 10\u003csup\u003e4\u003c/sup\u003e a.u.), both exhibiting\u0026thinsp;\u0026lt;\u0026thinsp;5% variation across cycles. These results collectively demonstrate the catalyst\u0026rsquo;s long-term durability (\u0026gt;\u0026thinsp;30 h) and structural robustness under industrially relevant conditions, providing a material foundation for engineering low-concentration methane catalytic combustion technologies.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec15\" class=\"Section2\"\u003e\n \u003ch2\u003e3.9 Structure-Activity Relationship Analysis\u003c/h2\u003e\n \u003cp\u003eThe methane oxidation activity of the catalyst exhibits a significant multidimensional correlation with structural parameters, surface chemical states, and redox kinetics, governed by the following synergistic mechanisms:\u003c/p\u003e\n \u003cp\u003e(1) Hierarchical Confinement Structure for Active Site Exposure\u003c/p\u003e\n \u003cp\u003eThe Pt-MnO\u003csub\u003e2\u003c/sub\u003e/m-Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e catalyst, synthesized via precipitation, achieves sub-nanometer Pt dispersion (HAADF-STEM particle size\u0026thinsp;\u0026lt;\u0026thinsp;2 nm) through dual confinement by mesoporous m-Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e (pore size\u0026thinsp;~\u0026thinsp;8 nm) and layered MnO\u003csub\u003e2\u003c/sub\u003e (sheet thickness\u0026thinsp;~\u0026thinsp;8 nm). The optimized BET surface area (28.1 m\u003csup\u003e2\u003c/sup\u003e/g, 38.4% higher than undoped samples) and increased mesopore volume (\u0026Delta;V\u0026thinsp;=\u0026thinsp;0.12 cm\u003csup\u003e3\u003c/sup\u003e/g) provide a topological foundation for high-density exposure of Mn\u003csup\u003e3+\u003c/sup\u003e-O\u003csub\u003ev\u003c/sub\u003e active sites (12% Ov concentration via XPS) and PtO-MnPt\u003csub\u003e3\u003c/sub\u003eO\u003csub\u003e6\u003c/sub\u003e interfaces (Fig. \u003cspan class=\"InternalRef\"\u003e7\u003c/span\u003eb) \u003csup\u003e[\u003cspan class=\"CitationRef\"\u003e38\u003c/span\u003e]\u003c/sup\u003e. Reduced crystallite size (12.3 nm via Scherrer equation) and elevated defect density (Williamson-Hall microstrain \u0026epsilon;\u0026thinsp;=\u0026thinsp;0.18%) lower oxygen migration barriers, enhancing reactant (CH\u003csub\u003e4\u003c/sub\u003e, O\u003csub\u003e2\u003c/sub\u003e) diffusion and adsorption.\u003c/p\u003e\n \u003cp\u003e(2) Pt-MnO\u003csub\u003e2\u003c/sub\u003e Solid Solution-Driven Oxygen Vacancy Proliferation and Lattice Oxygen Activation\u003c/p\u003e\n \u003cp\u003eXRD and Raman analyses confirm that Pt\u003csup\u003e2+\u003c/sup\u003e/Pt\u003csup\u003e4+\u003c/sup\u003e (ionic radius: 0.80 \u0026Aring;) incorporation into the MnO\u003csub\u003e2\u003c/sub\u003e lattice via solid solution mechanisms induces (001) interplanar contraction (\u0026Delta;d\u0026thinsp;=\u0026thinsp;0.03 \u0026Aring;, Bragg angle shift \u0026Delta;2\u0026theta;\u0026thinsp;=\u0026thinsp;0.2\u0026deg;) and a blue shift in Mn-O vibrational frequency (\u0026Delta;\u0026nu;\u0026thinsp;=\u0026thinsp;3 cm\u003csup\u003e\u0026ndash;1\u003c/sup\u003e, Raman peak: 572 \u0026rarr; 575 cm\u003csup\u003e\u0026ndash;1\u003c/sup\u003e). This lattice distortion drives Mn\u003csup\u003e3+\u003c/sup\u003e content from 75.22\u0026ndash;79.87% (XPS) through charge compensation (Eq. 1), simultaneously increasing O\u003csub\u003ev\u003c/sub\u003e concentration and forming dynamic Mn\u003csup\u003e3+\u003c/sup\u003e-Ov-Mn\u003csup\u003e4+\u003c/sup\u003e triple centers. H\u003csub\u003e2\u003c/sub\u003e-TPR reveals a 16 ℃ reduction in O\u003csub\u003ev\u003c/sub\u003e-mediated Mn\u003csup\u003e4+\u003c/sup\u003e \u0026rarr; Mn\u003csup\u003e3+\u003c/sup\u003e peak temperature (303 \u0026rarr; 287 ℃) and a 25% increase in hydrogen consumption, confirming that Ov acts as electron transfer bridges to accelerate lattice oxygen (Oₗₐₜₜ) activation and regeneration.\u003c/p\u003e\n \u003cp\u003e(3) Pt-Mn-O Interfacial Synergy in Oxygen Species Cycling Kinetics\u003c/p\u003e\n \u003cp\u003eHAADF-STEM and EDS verify the coexistence of PtO (interplanar spacing: 0.23 nm) and MnPt\u003csub\u003e3\u003c/sub\u003eO\u003csub\u003e6\u003c/sub\u003e (0.21 nm) at heterointerfaces on MnO\u003csub\u003e2\u003c/sub\u003e (Fig. \u003cspan class=\"InternalRef\"\u003e7\u003c/span\u003eb). This interface optimizes oxygen cycling via dual functionalities: (1) PtO serves as O\u003csub\u003e2\u003c/sub\u003e adsorption-dissociation sites, efficiently converting gaseous oxygen to adsorbed oxygen (O\u003csub\u003eads\u003c/sub\u003e); (2) MnPt\u003csub\u003e3\u003c/sub\u003eO\u003csub\u003e6\u003c/sub\u003e facilitates O\u003csub\u003eads\u003c/sub\u003e \u0026rarr; O\u003csub\u003elatt\u003c/sub\u003e conversion, increasing O\u003csub\u003e2\u003c/sub\u003e-TPD desorption capacity by 38%. The resulting \u0026ldquo;adsorption-lattice\u0026rdquo; dynamic equilibrium enhances Ov regeneration rates (kO\u003csub\u003ev\u003c/sub\u003e \u0026asymp; 0.15 s\u003csup\u003e\u0026ndash;1\u003c/sup\u003e, 2.3\u0026times; higher than undoped samples), ensuring continuous O\u003csub\u003elatt\u003c/sub\u003e participation in C\u0026ndash;H bond cleavage (CH\u003csub\u003e4\u003c/sub\u003e\u0026thinsp;+\u0026thinsp;O\u003csub\u003elatt\u003c/sub\u003e \u0026rarr; CO\u003csub\u003e2\u003c/sub\u003e\u0026thinsp;+\u0026thinsp;H\u003csub\u003e2\u003c/sub\u003eO\u0026thinsp;+\u0026thinsp;Ov) via the Mars-van Krevelen (MVK) mechanism \u003csup\u003e[\u003cspan class=\"CitationRef\"\u003e39\u003c/span\u003e\u0026ndash;\u003cspan class=\"CitationRef\"\u003e41\u003c/span\u003e]\u003c/sup\u003e.\u003c/p\u003e\n \u003cp\u003e(4) Structural Robustness and Long-Term Stability Mechanisms\u003c/p\u003e\n \u003cp\u003eDuring 30-hour stability testing at 230 ℃, the catalyst maintains a methane conversion rate of 98.2\u0026thinsp;\u0026plusmn;\u0026thinsp;0.5%, with post-cycling XRD showing negligible variation in (001) peak FWHM (0.35\u0026deg; \u0026plusmn; 0.02\u0026deg;) and crystallite size (12.3\u0026thinsp;\u0026plusmn;\u0026thinsp;0.5 nm). This stability originates from: (1) The rigid mesoporous m-Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e framework suppressing Pt sintering; (2) Topological confinement by layered MnO\u003csub\u003e2\u003c/sub\u003e alleviating redox-induced lattice stress; (3) Strong Pt-Mn interactions (XPS binding energy shift \u0026Delta;E\u0026thinsp;=\u0026thinsp;0.8 eV) preventing active component leaching. Consistent O\u003csub\u003e2\u003c/sub\u003e-TPD and H\u003csub\u003e2\u003c/sub\u003e-TPR profiles (peak temperature drift\u0026thinsp;\u0026lt;\u0026thinsp;5 ℃) further validate the self-healing capability of the oxygen cycling network.\u003c/p\u003e\n\u003c/div\u003e"},{"header":"4 Conclusions","content":"\u003cp\u003e(1) The synergistic confinement effect of mesoporous m-Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e and layered MnO\u003csub\u003e2\u003c/sub\u003e in the precipitated catalyst enables sub-nanometer Pt dispersion (particle size\u0026thinsp;\u0026lt;\u0026thinsp;2 nm via HAADF-STEM), achieving a BET surface area of 28.1 m\u003csup\u003e2\u003c/sup\u003e/g (vs. 20.3 m\u003csup\u003e2\u003c/sup\u003e/g for undoped samples) and mesopore volume increase of 0.12 cm\u003csup\u003e3\u003c/sup\u003e/g. This architecture significantly enhances methane and oxygen adsorption capacity, while reduced crystallite size (12.3 nm via Scherrer equation) and lowered reduction activation energy (H\u003csub\u003e2\u003c/sub\u003e-TPR peak temperature decreased by 16 ℃) collectively accelerate reaction kinetics.\u003c/p\u003e \u003cp\u003e(2) XRD and Raman analyses confirm that Pt\u003csup\u003e2+\u003c/sup\u003e/Pt\u003csup\u003e4+\u003c/sup\u003e incorporation into the MnO\u003csub\u003e2\u003c/sub\u003e lattice induces lattice contraction (Δd\u0026thinsp;=\u0026thinsp;0.03 \u0026Aring;) and Mn-O vibrational blue shift (Δν\u0026thinsp;=\u0026thinsp;3 cm\u003csup\u003e\u0026ndash;1\u003c/sup\u003e), driving Mn\u003csup\u003e3+\u003c/sup\u003e content to 79.87% (XPS) and oxygen vacancy concentration by 12%. The PtO-MnPt\u003csub\u003e3\u003c/sub\u003eO\u003csub\u003e6\u003c/sub\u003e heterointerface (interplanar spacings: 0.23/0.21 nm) accelerates oxygen cycling via a dual-functional mechanism: PtO facilitates O\u003csub\u003e2\u003c/sub\u003e adsorption-dissociation, while MnPt\u003csub\u003e3\u003c/sub\u003eO\u003csub\u003e6\u003c/sub\u003e mediates dynamic lattice oxygen migration. This synergy elevates oxygen vacancy regeneration rates by 2.3\u0026times; (O\u003csub\u003e2\u003c/sub\u003e-TPD desorption capacity increased by 38%), reducing the T\u003csub\u003e90\u003c/sub\u003e for methane oxidation to 226 ℃ (undoped: 260 ℃).\u003c/p\u003e \u003cp\u003e(3) Under continuous operation at 230 ℃ and a space velocity of 30,000 h\u003csup\u003e\u0026ndash;1\u003c/sup\u003e, the catalyst maintains a stable methane conversion rate of 98.2\u0026thinsp;\u0026plusmn;\u0026thinsp;0.5% over 30 hours. Post-cycling characterization reveals negligible changes in (001) peak FWHM (0.35\u0026deg; \u0026plusmn; 0.02\u0026deg;) and crystallite size (12.3\u0026thinsp;\u0026plusmn;\u0026thinsp;0.5 nm), demonstrating effective suppression of sintering and active component leaching through mesoporous confinement and strong Pt-Mn bonding.\u003c/p\u003e \u003cp\u003e(4) The catalyst achieves efficient elimination of low-concentration methane (1000 ppm) at a low noble metal loading (0.5 wt% Pt), offering a viable solution for industrial exhaust treatment. This study elucidates a multidimensional mechanism of \u0026ldquo;confinement-driven dispersion\u0026ndash;oxygen vacancy proliferation\u0026ndash;interfacial synergy\u0026rdquo; establishing a theoretical foundation for designing advanced heterogeneous methane combustion catalysts.​\u003c/p\u003e"},{"header":"Declarations","content":"\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eZeng Xiaoyi wrote the main manuscript text , Zhang Ruikun prepared figures 1-3 and Xiang Xianbing prepared figures 1-3. All authors reviewed the manuscript.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eAkbari E, Alavi S M, Rezaei M, et al. Preparation and evaluation of A/ BaO‐MnO\u003csub\u003ex\u003c/sub\u003e catalysts (A: Rh, Pt, Pd, Ru) in lean methane catalytic combustion at low temperature[J]. International Journal of Energy Research, 2021, 46(5): 6292-6313.\u003c/li\u003e\n\u003cli\u003eCao Y, Su T, Ding Y, et al. 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Applied Catalysis B: Environmental, 2016, 181: 236-248.\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Hierarchical confinement, Pt-MnO2 interface, Oxygen vacancy, Methane catalytic combustion, Stability","lastPublishedDoi":"10.21203/rs.3.rs-6367896/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-6367896/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eIn this study, hierarchically confined Pt-MnO\u003csub\u003e2\u003c/sub\u003e/m- Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e catalysts were synthesized via a precipitation method using MnO\u003csub\u003e2\u003c/sub\u003e- Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e as promoters, and their methane catalytic combustion performance and structure-activity relationships were systematically investigated. The results demonstrate that the 0.5 wt% Pt-loaded Pt-MnO\u003csub\u003e2\u003c/sub\u003e/m- Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e catalyst achieved 90% methane conversion at 228 ℃ (T\u003csub\u003e90\u003c/sub\u003e). The enhanced performance is attributed to three synergistic mechanisms: (1) Pt doping induced lattice contraction in MnO\u003csub\u003e2\u003c/sub\u003e (XRD revealed a 0.03 \u0026Aring; reduction in the (001) interplanar spacing), which facilitated the formation of \u003csup\u003e3+\u003c/sup\u003e-oxygen vacancy pairs (XPS indicated a Mn\u003csup\u003e3+\u003c/sup\u003e- content of 79.87%); (2) The PtO-MnPt\u003csub\u003e3\u003c/sub\u003eO\u003csub\u003e6\u003c/sub\u003e interfacial structure (HAADF-STEM confirmed lattice spacings of 0.23/0.21 nm) accelerated oxygen species cycling, with lattice oxygen desorption capacity (O\u003csub\u003e2\u003c/sub\u003e-TPD) increasing by 38% compared to undoped samples; (3) The mesoporous m-Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e carrier provided effective confinement, achieving a high specific surface area (28.1 m\u003csup\u003e2\u003c/sup\u003e/g) and sub-nanometer Pt dispersion (particle size\u0026thinsp;\u0026lt;\u0026thinsp;2 nm). Under conditions of 1000 ppm CH\u003csub\u003e4\u003c/sub\u003e and a space velocity of 30,000 h\u003csup\u003e\u0026ndash;1\u003c/sup\u003e, the catalyst maintained a methane conversion rate of 98.2\u0026thinsp;\u0026plusmn;\u0026thinsp;0.5% during continuous operation for 30 hours. Post-cycling characterization revealed stable crystalline structure (XRD full width at half maximum of 0.35\u0026deg;\u0026plusmn;0.02\u0026deg;) and grain size (12.3\u0026thinsp;\u0026plusmn;\u0026thinsp;0.5 nm), confirming its robustness for industrial applications. This study provides theoretical and experimental foundations for the rational design of highly efficient catalysts for low-concentration methane elimination.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e","manuscriptTitle":"Interface Engineering of Hierarchically Confined Pt-MnO 2 /m-Al 2 O 3 Catalysts and Their Performance and Mechanism in Low-Temperature Methane Catalytic Combustion","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-04-25 14:19:41","doi":"10.21203/rs.3.rs-6367896/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"fb6b0b45-e489-4a87-a953-ab108ec10d58","owner":[],"postedDate":"April 25th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2025-05-31T22:23:11+00:00","versionOfRecord":[],"versionCreatedAt":"2025-04-25 14:19:41","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-6367896","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-6367896","identity":"rs-6367896","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}