Pt nanoparticles breathe and reversibly detach from Al2O3 in hydrogen

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Pt nanoparticles are particularly susceptible to structural relaxation and disordering induced by adsorbed CO and H 2 . In a hydrogenated state, theoretical models have predicted not only the reshaping of Pt nanoparticles, but also their shift away from the surface of their metal oxide support. In this work we examined the dynamic behavior of well-dispersed 1–3 nm diameter Pt nanoparticles under hydrogenation conditions. Using time-resolved X-ray diffraction and pair distribution function analysis allied to a modulated-excitation approach, we provide direct experimental evidence of the simultaneous “breathing” of the Pt nanoparticles and their detachment from the Al 2 O 3 support under H 2 atmosphere. These dynamic structural changes are shown to be size-dependent, to occur in both gas phase (150°C) and liquid phase (cyclohexane, 70°C), and to be reversible, thus ensuring the stability of the catalyst under hydrogenation conditions. Gaining direct structural evidence of the ductile behavior of supported metal nanoparticles in reactive chemical environments is a groundbreaking step towards precise structural control of catalysts under reaction conditions. Physical sciences/Chemistry/Catalysis/Heterogeneous catalysis Physical sciences/Materials science/Nanoscale materials/Nanoparticles Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Introduction Supported metal nanoparticles (NPs) are pivotal as heterogeneous catalysts in numerous industrial and environmental processes. 1 – 6 Early research established structure-activity correlations 7 and rationalized the impact of NPs size on catalytic activity and selectivity. 8 , 9 Metal NPs are also active entities with their own dynamic behavior in the presence of adsorbates and/or under reaction conditions. 10 – 13 Understanding the structural evolution of metal NPs in various reaction environments is crucial for precise control over their size and reactivity, both of which are essential for catalyst design, as well as for the regeneration of deactivated catalysts. 14 , 15 Platinum NPs are among the most studied catalytic systems. The CO-induced reconstruction of Pt surfaces and of Pt NPs is a classic example of adsorbate-induced surface reconstruction. 11 , 16 – 21 Similarly, H 2 can induce electronic and morphological restructuring of supported Pt clusters. 22 – 26 At room temperature and sub-ambient pressure, H 2 splits on Pt surfaces, forming various Pt hydrides. In nanoscale Pt particles, hydride formation is accompanied by structural reconstruction, as demonstrated by Mager-Maury et al. 27 using density functional theory (DFT) calculations on a model Pt 13 cluster supported on γ-Al 2 O 3 . Their findings revealed that, as the H/Pt ratio increases, the Pt 13 cluster transitions from a biplanar morphology, strongly interacting with the support, to a more symmetric cuboctahedral structure, which almost detaches from the support. Similar behavior was observed for Pt 37 clusters on graphene, 23 suggesting a universal nature of this process across diverse NP sizes and supports of very different nature. The available theoretical calculations for Pt clusters on γ-Al 2 O 3 27 propose three primary descriptors for this restructuring phenomenon as a function of the hydrogen partial pressure: i) changes in the relative amounts of linear and bridged Pt hydrides, ii) elongation of the average Pt-Pt distance (i.e. the "breathing" of the Pt NPs), and iii) increased Pt-support distance (i.e. the detachment of the Pt NPs). To date, only limited experimental evidence supports these theoretical predictions. As regards the amount of Pt hydrides, titration experiments found values of the H/Pt surf ratio greater than 1 for ultra-dispersed Pt NPs, 28 , 29 in good agreement with models where the Pt NPs are completely hydrogenated. Recently, we provided experimental evidence of the conversion of linear Pt hydrides into bridged species on 5 wt% Pt/Al 2 O 3 using Fourier transform infrared (FT-IR) spectroscopy and inelastic neutron scattering (INS) spectroscopy, 30 – 32 in excellent agreement with the theoretical prediction. 27 With respect to structural descriptors, only the breathing of Pt NPs in the presence of H 2 was confirmed experimentally. X-ray absorption spectroscopy (XAS) showed a contracted fcc lattice 33 and higher structural disorder in naked Pt NPs compared to bulk Pt, 30 , 34 – 37 while hydrogen adsorption induces lattice relaxation and more structural order (e.g. restoring of the fcc symmetry). In contrast, apart from the mobility of Pt clusters detected by environmental STEM under H 2 , 38 the direct observation of the H 2 -induced detachment of Pt NPs from the support remains elusive. This is due to the minute structural effects associated with NP detachment from the support, which to date have not been observed by either XAS or synchrotron X-ray pair distribution function (PDF) analysis, 39 – 41 despite the latter is able to describe the structural changes in 1–3 nm sized Pt NPs on Al 2 O 3 induced by adsorbates from the gas phase. 42 Finally, the reversibility of the H 2 -induced restructuring and its dependence on the reaction environment are also unexplored yet critical areas, with practical implications for catalyst stability and performance under hydrogenation conditions. To capture experimentally all these dynamic aspects of NPs restructuring, we combined high-energy x-ray diffraction (XRD) and PDF analysis, in a modulated excitation experimental approach, to study two industrial Pt/Al 2 O 3 catalysts characterized by different particle size distributions, previously investigated by IR spectroscopy and INS. 30 – 32 , 43 The experiments were designed to recreate the conditions in which NPs are expected to either be completely hydrogenated and (partially) detached from the support or, conversely, to strongly interact with the support. The combination of structure-sensitive techniques, experiment design and advanced data analysis allowed us to present conclusive evidence of the simultaneous H 2 -induced breathing and reversible (partial) detachment of Pt NPs in both gas and liquid environments. These findings provide experimental proof of the ductility of supported NPs in the presence of adsorbates in terms of particle reconstruction, opening up fascinating new perspectives on their catalytic behavior in various reaction environments. Experimental details and data analysis Catalyst synthesis and preliminary characterization The two 5 wt% Pt/Al 2 O 3 catalysts investigated in this work were prepared by Chimet S.p.A. (Viciomaggio, Italy), following a deposition-precipitation method 44 using a high-surface-area transitional alumina as a support (SSA = 116 m 2 g − 1 ; pore volume = 0.41 cm 3 g − 1 ; mixed phase). These two catalysts differ in whether or not a reduction step was performed after Pt deposition: one catalyst (hereafter called PtAl) was not pre-reduced and so the Pt phase is fully oxidized in the pristine sample; the other (hereafter PtAl(R)) was reduced using sodium formate as reducing agent, hence, the Pt phase is metallic, but passivated by a thin oxide layer. In both cases, after the synthesis the catalysts were thoroughly washed with water and then dried at 120°C overnight. The nominal Pt dispersion was determined by H 2 /O 2 titration 45 on samples reduced at 120°C, and was D = 63%, and D = 21% for PtAl and PtAl(R), respectively. Transmission Electron Microscopy (STEM) imaging was performed using a probe-corrected JEOL JEM ARM-200 F (NeoARM) microscope equipped with a cold FEG gun operated at 200 keV. Scanning transmission electron microscopy (STEM) high-angle annular dark-field (HAADF) images were collected at 68 mrad < α < 280 mrad. Approximately 800 particles were counted in the HAADF-STEM images of each sample in order to estimate the particle size distribution using the approach by Alxneit. 46 In-situ XRD measurements In situ X-ray diffraction measurements were performed at beamline ID15A 47 at the ESRF synchrotron (Grenoble, France) using an X-ray beam energy of 98 keV (λ = 0.1265 Å) and a photon-counting Pilatus3X 2M CdTe detector (Dectris, Switzerland) positioned at a 330 mm sample-to-detector distance. Beam size was 100×100 µm 2 (vertical×horizontal) and the average flux on the sample was 10 12 photons s − 1 . A stainless-steel cell designed to feed the gas/liquid bottom-up through a 9 mm 3 catalyst bed provided leak-tight operation, minimal dead volume upon switching flows, low scattering background, and a wide exit angle for measurements enabling PDF analysis (see Supporting Information for details). The sample (approximately 30 mg) was placed in the cell between two quartz wool plugs used to both diffuse the gas/liquid feed and suppress sample movement. Throughout the following protocol, we collected scattering data continuously with a time resolution of 1 s/pattern. The sample was kept 1 min at ambient temperature under Ar (gas phase experiment) or Ar-saturated cyclohexane (liquid phase experiment). Then the temperature was increased at a rate of 10°C/min to 150°C (gas phase) or 70°C (liquid phase), under Ar (flow of 100 ml/min, gas phase) or Ar-saturated cyclohexane (1 ml/min, liquid phase). At this point, the gas flowing through the cell was changed to 5 vol% H 2 /Ar (gas phase) or to H 2 -saturated cyclohexane (liquid phase) to perform an isothermal reduction for 30 min. Lastly, the sample was washed in Ar (gas phase) or Ar-saturated cyclohexane (liquid phase) at the same temperature for 30 min. Modulated excitation experiments were started at this point by exposing the sample to repeated cycles of 5 vol% H 2 /Ar (10 min) and Ar (10 min) or H 2 -saturated cyclohexane (5 min) and Ar-saturated cyclohexane (5 min). Reference data such as blank Al 2 O 3 in different phases were collected in the same conditions. The use of a stainless steel valve and a ceramic valve (VICI AG, Switzerland) enabled repeated, no-dead time switching between the two different gas/liquid flows. Gas feeds were delivered through calibrated mass flow meters (Bronkhorst, Netherlands) and stainless steel tubing (1/16’’) while liquid feeds were circulated by a calibrated peristaltic pump (Spetec, Germany) installed upstream of the cell and Teflon and stainless steel tubing. Two glass bottles were used as reservoirs for cyclohexane solvent (HPLC purity, Sigma Aldrich) and were fitted with a frit to allow for saturation with pure gases (Ar or H 2 , both 99.999 vol%). Cyclohexane was selected as model solvent because it can be considered non-interacting with the catalyst and also in order to remain consistent with the previous study using IR spectroscopy to analyse Pt hydrides on these catalysts. 32 A quadrupole mass spectrometer (Hiden Analytical, UK) connected to the outlet of the cell was used to monitor gas feed and its evolution in the gas phase experiments. Data reduction and PDF calculation Two-dimensional X-ray scattering data were azimuthally integrated using pyFAI. 48 Data were corrected for the flat-field response and spatial distortion of the detector, 49 X-ray beam polarization, and variations in the incident photon flux. Azimuthally integrated data were converted to PDF using PDFgetx3, 50 using a range of momentum transfer 0.8 ≤ Q ≤ 22 Å −1 and the scattering patterns of the empty cell and/or blank Al 2 O 3 support collected under identical conditions as background. This enabled isolating Pt-Pt correlations related to the NPs from interatomic correlations involving the support. Data fitting and simulation Structural models were fitted to XRD powder patterns and PDF data using Topas v7. 51 Crystallite size was estimated either from fits to PDF data using a spherical-particle dampening model or from fitting high-resolution XRD data, collected at the ID22 beamline at the ESRF (see Supporting Information for details). 52 With the exception of the pristine PtAl sample (see below), the PDF data were fitted by Gaussian peaks corresponding to Pt-Pt distances in the Pt fcc structure, using lmfit. 53 Additionally, they were compared to a set of calculated PDFs corresponding to a series of Pt x H y /γ-Al 2 O 3 models, consisting of Pt x H y nanoparticles of various sizes (x = 13, 34, 55) and hydrogen coverages supported on a slab of dehydroxylated γ-Al 2 O 3 (100) surface. Notably, the local structure of γ-Al 2 O 3 is indistinguishable from that of the other alumina phases (Figure S2c). The most stable structures of the Pt 13 H y /γ-Al 2 O 3 models were obtained previously by using DFT calculations based on velocity scale molecular dynamics followed by a quenching procedure, 27 while the larger models (x = 34 and x = 55) were obtained by static optimization because of computational cost. The Pt 34 H 54 /γ-Al 2 O 3 , Pt 55 H 44 /γ-Al 2 O 3 and Pt 55 H 91 /γ-Al 2 O 3 structures were adopted previously to explain the behavior of supported Pt NPs in the same PtAl sample in different hydrogenation conditions, 31 while the naked Pt 34 /γ-Al 2 O 3 and Pt 55 /γ-Al 2 O 3 systems were constructed as detailed in Supporting information. The selected sizes of the Pt clusters, which correspond to about 1 nm (Pt 13 ) to 1.5 nm (Pt 55 ), represent the best compromise between the range of STEM sizes and the limitations imposed by computational costs. Total and partial PDFs of the Pt x H y /γ-Al 2 O 3 models were calculated over the same range of Q used for the experimental PDF data using DebyeCalculator. 54 Results and discussion Characterization of the pristine catalysts The two Pt/Al 2 O 3 catalysts show similar homogeneous distribution of Pt NPs but different average NP size (Fig. 1 ). The pre-reduced sample, PtAl(R), displays a log-normal distribution with a mode around 3.0 nm (Fig. 1 a-c), while PtAl has smaller particles, with a bimodal distribution peaking at about 1.0 nm and 2.2 nm (Fig. 1 b-d). Both distributions are narrow enough to ensure reliable XRD and PDF analysis. The XRD patterns of the catalysts (Fig. 2 a and Fig. 2 c) are dominated by the peaks of the Al 2 O 3 support, which consists of a mixture of the ™- and θ-phases with a minor contribution from γ-Al 2 O 3 (see Figure S2 in Supporting Information for details). To isolate the contribution of Pt in the patterns of PtAl and PtAl(R), the data of the same Al 2 O 3 support used to prepare the two catalysts was subtracted from those of the two catalysts. The difference pattern of PtAl(R) (Fig. 2 a) exhibits clear diffraction peaks of face-centered cubic ( fcc ) Pt. An average crystallite size of 2.8 nm was estimated based on the XRD peak widths (Table S1 ). In contrast, the difference pattern of PtAl (c) shows broader, weaker peaks (ca. 2.6 and 4.0 Å −1 ), which can be attributed to an oxidized phase, 39 , 55 in line with previous measurements on the same sample 30 and with observations of well-dispersed metal hydroxide in catalysts prepared by deposition-precipitation reported in the literature. 56 – 59 Figure 2 b and Fig. 2 d compare the PDF curves of both catalysts to that of the Al 2 O 3 support. Figure S3 shows the same data in a wider R range, along with the fit used to estimate the NPs size. After background subtraction, the difference PDF reflects only interatomic distances within the Pt NPs. For PtAl(R) (Fig. 2 b), the most intense peaks appear at ca. 2.76, 4.79 and 7.32 Å, corresponding to the 1st, 3rd and 7th shell Pt-Pt distances in the fcc Pt phase (i.e. those with the highest multiplicity). The intensity falloff as a function of R can be modeled using a spherical particle diameter of 3.3 nm (Table S1 ), in agreement with the estimate from XRD and consistent with the particle size estimated from STEM. The difference PDF of PtAl contains only a few clearly discernible peaks up to 6 Å (Fig. 2 d), among which the peak at about 2.0 Å is typical of Pt-O distances in Pt oxide/hydroxide. Isothermal reduction in gas and liquid phase The reduction of the catalysts was performed in H 2 under isothermal conditions in both gas phase (H 2 /Ar, 150°C) and liquid phase (H 2 -saturated cyclohexane, 70°C). No changes were observed for PtAl(R) (Figure S4-S5 and Table S1 ), confirming that the Pt phase was already reduced and a possible oxide passivation layer was undetectable. In contrast, the reduction of the Pt-oxide phase was clearly observed for PtAl, in both gas (Fig. 3 ) and liquid phases (Figure S6). Difference patterns (Fig. 3 c and Fig. 3 d) highlight the relatively small changes to the XRD patterns during reduction in H 2 /Ar at 150°C. Both XRD and PDF data show that the Pt-oxide phase is gradually reduced to metallic fcc Pt by H 2 . Difference XRD (c) shows broad negative peaks at the positions assigned to PtO 2 (around 2.6 and 4.0 Å −1 ), which pinpoint its disappearance. Positive peaks appear at positions characteristic for metallic Pt (2.8, 3.2, 4.5, 5.3 and 7.0 Å −1 ). In the PDF (Fig. 3 d), the sharp peaks corresponding to the 1st, 3rd, and 7th shell Pt-Pt distances emerged clearly during reduction. From the temporal evolution of their normalized intensity, we obtained kinetic information on the Pt oxide reduction (Fig. 4 a): reduction by H 2 in the gas phase was completed within 10 s, while it was almost ten times slower in the liquid phase. We attribute this difference to a combination of factors: the higher reduction temperature in the gas phase experiment (150°C vs. 70°C, the latter imposed by the boiling point of the solvent), the poor solubility and the lower diffusivity of H 2 in cyclohexane, resulting in lower H 2 concentration in the liquid-phase experiment. At the end of the reduction process, and in excess of H 2 , the Pt phases in PtAl were identical regardless of the reaction environment and temperature (dotted lines in Fig. 4 b). Fits to the background-subtracted PDFs (solid lines in Fig. 4 b) returned very similar lattice parameters and a NP size of 2.3 ± 0.1 nm after both liquid and gas-phase reductions (Table S1 ). This provides compelling evidence that the Pt oxide phase in PtAl is completely reduced in cyclohexane also at 70°C, and that the reaction environment does not affect Pt particle size, which remains very close to the center of the distribution evaluated by STEM on the pristine (unreduced) PtAl catalyst (Fig. 1 ). The same applies also to PtAl(R) (Figure S7), although the average NP size remains far larger than in the reduced PtAl (Table S1 ). The PDF patterns of the reduced catalysts (Fig. 4 b), where the short-range order is largely dictated by bulk fcc Pt, are well reproduced by the highly symmetric Pt x H y /Al 2 O 3 cuboctahedral models from DFT calculations, 27 in which the Pt NPs are surrounded by hydrogen and detached from the alumina support (Pt 55 H 91 /Al 2 O 3 in Fig. 4 ). The choice of hydrogenated Pt NPs models is justified by the experimental evidence from IR spectroscopy in both the gas and the liquid phase 30 , 32 and INS in gas phase 31 that, under very similar experimental conditions, various surface Pt hydride species exist on these catalysts. Pt NPs breathe and detach from the support in the presence of H 2 : direct structural evidence Hydrides are unstable in the absence of H 2 and are decomposed once the surrounding is changed to Ar after reduction; as a consequence, the Pt NPs undergo surface relaxation accompanied by disordering. Figure 5 a compares the simulated PDF for a supported Pt 55 NP dehydrogenated and in two different hydrogenation states. Supported Pt 34 and Pt 13 NPs behave very similarly (Figure S8). In the high H-coverage regime (Pt 55 H 91 /Al 2 O 3 , Fig. 5 b), the simulated PDF peaks are sharp and largely determined by the Pt fcc structure. In the naked state (Pt 55 /Al 2 O 3 , Fig. 5 c), the Pt NP adopts an irregular morphology, strongly interacting with the alumina support. Correspondingly, the simulated PDF shows a more contracted first shell Pt-Pt peak compared to the hydrogenated counterpart, and completely smeared-out higher-shell Pt-Pt peaks. In an intermediate hydrogenation state (Pt 55 H 44 /Al 2 O 3 ) the simulated PDF is intermediate. This effect is more pronounced upon decreasing the Pt particle size (Figure S8). The experimental PDF patterns of PtAl in the fully hydrogenated (i.e. under H 2 /Ar at 150°C) and dehydrogenated (i.e. under Ar at 150°C) states (Fig. 5 c) suggest that analogue changes indeed occur to the Pt NPs during dehydrogenation. The difference PDF (diff in Fig. 5 c) reveals a contraction of the first Pt-Pt distance of about 0.9% and a higher dispersion of the 3rd and 5th shell Pt-Pt peaks, closely resembling the simulated difference pattern for a Pt 55 NP (diff in Fig. 5 a). The contraction of the first shell Pt-Pt distance upon removal of H 2 can be interpreted as the breathing of the Pt NP induced by removal of hydride species, as well as the more irregular morphology responsible for the disappearance of the higher-shell Pt-Pt peaks. To provide also kinetic information and to emphasize structural changes with increased sensitivity, we performed a series of experiments after the isothermal reduction adopting the modulated excitation (ME) approach. 60 , 61 The raw (i.e. not Al 2 O 3 background subtracted) PDF data calculated from the XRD patterns collected during the ME experiment were analyzed to track the breathing of the Pt NPs in the presence/absence of H 2 , and their interaction with the support. In this latter case, difficulties arise because only very small changes can be expected to affect the Pt-support distances (less than 0.2 Å). 27 We focused on the region 2.5–3.75 Å range of the PDF (Fig. 5 d), which consists mostly of two peaks: the peak at 2.76 Å is dominated by the 1st shell Pt-Pt correlation, while that at 3.33 Å is mainly represented by Al-Al correlations from the Al 2 O 3 support (Figure S9). It is worth noticing that the intensity of the latter is negligible in the simulated PDF patterns of Pt 55 H x /Al 2 O 3 (Fig. 5 a) because the models comprise only a thin slab of Al 2 O 3 . Both peaks also contain information on Pt-support correlations: short and very heterogeneous Pt-support contributions, (Pt-supp) short , predominate for Pt NPs in strong interaction with the support (Figure S10a), while longer Pt-support distances are found above 3.2 Å for hydrogenated NPs, (Pt-supp) long (Figure S10b). Attempts to fit the data in the 2.5–3.75 Å range with four components (Pt-Pt + Al 2 O 3 +(Pt-supp) short + (Pt-supp) long ) were unstable, especially due to the strong parameter correlation between the Pt-Pt and (Pt-supp) short contributions. Therefore, we used three gaussian contributions (Fig. 5 e). The position of the first peak (blue) accounts for the first shell Pt-Pt distance; its full width at half maximum (FWHM) indicates the relative importance of the (Pt-supp) short contribution, i.e. the larger the FWHM, the larger the (Pt-supp) short contribution. The second gaussian contribution (grey) accounts for the Al 2 O 3 support and its parameters were fixed during the fit to the values obtained fitting the pattern of blank Al 2 O 3 . The amplitude of the third contribution (violet) estimates the relative weight of the (Pt-supp) long contribution, i.e. the different degree of interaction between the Pt NP and the Al 2 O 3 support. In the gas phase experiment at 150°C, the first shell Pt-Pt distance of PtAl equals that of bulk Pt (2.774 Å) at the end of the reduction step (Fig. 6 a). This distance contracts in the absence of hydrogen by ca. 0.7 ± 0.1% with respect to the hydrogenated situation and expands in its presence by the same amount, in a reproducible and reversible way over the ten modulation cycles. It is worth noticing that during the half cycles without H 2 the Pt-Pt distance does not decrease to its H 2 -equilibrated value, indicating that the 10-min Ar flushing phase is insufficient to completely remove the Pt hydride species. For PtAl(R) in H 2 (Fig. 6 c), the Pt-Pt distance is slightly expanded with respect to the bulk. It behaves similarly to PtAl during dehydrogenation, but with a smaller perturbation of the Pt-Pt bond (0.2 ± 0.1%), as expected from its larger, less ductile NPs. The NP breathing in both catalysts is not very pronounced but can be followed very precisely by these PDF data. Variations of the FWHM of the first gaussian contribution and of the amplitude of the (Pt-supp) long contribution are smaller than those of the Pt-Pt distance. To increase the signal-to-noise ratio, we report the variations of these two parameters after averaging data over ten cycles for PtAl in Fig. 6 b and for PtAl(R) in Fig. 6 d. For PtAl, the FWHM of the first peak increases by ca. 7 ± 1% of its original value upon H 2 removal, revealing that the (Pt-supp) short contribution becomes relevant in the inert (Ar) environment when hydrides are removed. Simultaneously, the amplitude of the (Pt-supp) long contribution decreases by 23 ± 1%. Therefore, the inert atmosphere promotes the decomposition of hydride species and the interaction of the NP with the support. While statistically relevant, the smaller variations of all three parameters for PtAl(R) are attributed to the larger particles in this sample, which are less prone to detachment from the support. Taken together, these two observations provide experimental evidence that upon variation of hydrogen coverage, Pt NPs not only breathe but also move relative to the support. The distance from the support increases in the presence of H 2 and hydride species, and decreases when hydrides are removed. Similar behavior is observed in the liquid environment (Fig. 7 ), but both breathing and movement relative to the support are less pronounced and kinetically slower than in the gas phase. The low H 2 concentration in the liquid phase and competition between H 2 and the solvent for adsorption sites at the Pt surface may both contribute to this. However, the behavior can be still captured precisely by the ME experiment: the Pt-Pt distance of NPs in PtAl changes by 0.3 ± 0.1% and the amplitude of (Pt-supp) long by 3 ± 1%. Observation of similar phenomena in the presence of a solvent and in the gas phase indicates that the structural / morphological reconstruction is a general feature of Pt NPs. Our data demonstrate that supported Pt NPs subjected to a reversible hydrogenation change their structure and distance from the support. As hydrogenated Pt NPs interact less strongly with the Al 2 O 3 support, they might become more available for interaction with adsorbates, including substrates to be hydrogenated. This has implications for a better understanding and control of the sustained stability of hydrogenation catalysts, since the detachment of the Pt NPs from the Al 2 O 3 support seems to be facilitated by hydrogen adsorption and could be a first step towards their mobility and leaching from the support, especially in liquid phase. The reproducibility of the modulation cycles in both gas and liquid phase, however, indicates that this must be a slow process under these experimental conditions and compared to the time scale of the ME experiments. Conclusions In this study, we provide experimental evidence of the simultaneous H 2 -induced breathing and movement of well-dispersed Pt nanoparticles (NPs) relative to their alumina support. Both phenomena, previously predicted only by theoretical models, were captured directly with unprecedented accuracy using high-energy XRD and total scattering PDF techniques, combined with a concentration modulation experimental approach and an experimental design aimed at reproducing conditions where Pt NPs are either completely hydrogenated or bare. Our findings reveal that both phenomena occur in both gas- and liquid-phase environments and with a magnitude highly correlated with the size of the NPs. Remarkably, the process is fully reversible over the time scale of our experiment, demonstrating the stability of the catalyst towards further mobility or even leaching. A better understanding of the dynamic behavior of metal NPs in the presence of adsorbates may open exciting opportunities for their rational control under reaction conditions. In this respect, our work not only validates the possibilities suggested by theoretical predictions, but also sets a new benchmark for experimental studies in the field of heterogeneous catalysis with supported metal NPs. It introduces a methodological approach to accurately track modifications at the metal-support interface in gas and liquid environments, where catalysis often occurs. Declarations Acknowledgments D.B., S.C., E.G. and D.F. acknowledge financial support from ESRF and PSI. All authors acknowledge the ESRF for providing beamtime through proposals CH-6371 and IH-CH-1722 ( https://doi.org/10.15151/ESRF-ES-1025993103 ; https://doi.org/10.15151/ESRF-ES-1267577360 ). D.B. and S.C. thank the Partnership for Soft Condensed Matter (Grenoble, France) for supporting preparation of the experiments. 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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-5912049","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":410301973,"identity":"ff391d1f-c21b-4917-8d34-748b5a2dc52c","order_by":0,"name":"Stefano Checchia","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAABAElEQVRIiWNgGAWjYJCCD2BSAogZGyQY+EGcCgY53OrZGBhnoGiRbAAyzjAYE62FgcHgAAEt8vObDzb83GHDwD+7+eCHnzss5I2Ptz/7cIDBIB+XFoNjbImNvWfSGCTuHEuW7D0jYbjtzBnjGUAtlg24tLDxmD/gbTvMYCCRY8bM2CbBuO1GDjPzB4Y/Bjgd1sb/sfEvWEv+N5AW+83znz9mANqCUwvDMR7GZqgtbCAtiRskgF7Hp8XgWJphs2xbGo/EjTRjyd42ieQZZ3KAWgxwa5FvPvyw8W2bjRz/jOSHH3621dn2tx8HOqwCj8OggAfddkIaRsEoGAWjYBTgAwCrCVSPLfooxwAAAABJRU5ErkJggg==","orcid":"https://orcid.org/0000-0003-0499-4885","institution":"ESRF - The European Synchrotron","correspondingAuthor":true,"prefix":"","firstName":"Stefano","middleName":"","lastName":"Checchia","suffix":""},{"id":410301974,"identity":"28adbcd7-1208-4d8a-a8a0-33c01fda5c2e","order_by":1,"name":"Daniele Bonavia","email":"","orcid":"","institution":"Paul Scherrer Institut","correspondingAuthor":false,"prefix":"","firstName":"Daniele","middleName":"","lastName":"Bonavia","suffix":""},{"id":410301975,"identity":"12e74c14-acf2-41f6-9f07-db9683eb5bd0","order_by":2,"name":"Davide Ferri","email":"","orcid":"https://orcid.org/0000-0002-9354-5231","institution":"Paul Scherrer Institut","correspondingAuthor":false,"prefix":"","firstName":"Davide","middleName":"","lastName":"Ferri","suffix":""},{"id":410301976,"identity":"fa06d5ef-023f-44d7-b83c-2839ed5ca6b9","order_by":3,"name":"Ivo Alxneit","email":"","orcid":"https://orcid.org/0000-0002-9389-9849","institution":"Paul Scherrer Institut","correspondingAuthor":false,"prefix":"","firstName":"Ivo","middleName":"","lastName":"Alxneit","suffix":""},{"id":410301977,"identity":"f2af2461-7984-4cb0-b3df-748458543a9e","order_by":4,"name":"Elena Groppo","email":"","orcid":"https://orcid.org/0000-0003-4153-5709","institution":"","correspondingAuthor":false,"prefix":"","firstName":"Elena","middleName":"","lastName":"Groppo","suffix":""},{"id":410301978,"identity":"9cfcc9a2-8697-4081-9dd4-def770cf3855","order_by":5,"name":"Alberto Ricchebuono","email":"","orcid":"","institution":"University of Turin","correspondingAuthor":false,"prefix":"","firstName":"Alberto","middleName":"","lastName":"Ricchebuono","suffix":""},{"id":410301979,"identity":"f9bb8343-4750-4927-a331-7b6b9cc139fc","order_by":6,"name":"Paolo Lazzarini","email":"","orcid":"","institution":"University of Turin","correspondingAuthor":false,"prefix":"","firstName":"Paolo","middleName":"","lastName":"Lazzarini","suffix":""},{"id":410301980,"identity":"1ba53e1a-dd68-4473-ba01-686e2515575c","order_by":7,"name":"Eleonora Vottero","email":"","orcid":"","institution":"University of Turin","correspondingAuthor":false,"prefix":"","firstName":"Eleonora","middleName":"","lastName":"Vottero","suffix":""},{"id":410301981,"identity":"b7ffedb7-3742-41cf-917a-7911a09bca14","order_by":8,"name":"Riccardo Pellegrini","email":"","orcid":"https://orcid.org/0000-0001-8989-7616","institution":"Chimet S.p.A.","correspondingAuthor":false,"prefix":"","firstName":"Riccardo","middleName":"","lastName":"Pellegrini","suffix":""},{"id":410301982,"identity":"58363663-68a7-470f-b076-4b032a66c3d1","order_by":9,"name":"Andrea Piovano","email":"","orcid":"https://orcid.org/0000-0002-5005-6307","institution":"Institut Laue-Langewin (ILL)","correspondingAuthor":false,"prefix":"","firstName":"Andrea","middleName":"","lastName":"Piovano","suffix":""},{"id":410301983,"identity":"83b3941e-b1e0-4376-a038-4d83794bdadd","order_by":10,"name":"Catherine Dejoie","email":"","orcid":"https://orcid.org/0000-0003-3313-3515","institution":"Structure of Materials Group, ESRF-The European Synchrotron","correspondingAuthor":false,"prefix":"","firstName":"Catherine","middleName":"","lastName":"Dejoie","suffix":""},{"id":410301984,"identity":"0b76db7f-9272-428a-8ed9-64435b3309d9","order_by":11,"name":"Céline Chizallet","email":"","orcid":"https://orcid.org/0000-0001-5140-8397","institution":"IFP Energies nouvelles","correspondingAuthor":false,"prefix":"","firstName":"Céline","middleName":"","lastName":"Chizallet","suffix":""},{"id":410301985,"identity":"d3dc6db2-eecd-4c0a-8399-02c4925f8fd2","order_by":12,"name":"Pascal Raybaud","email":"","orcid":"","institution":"IFP-Lyon","correspondingAuthor":false,"prefix":"","firstName":"Pascal","middleName":"","lastName":"Raybaud","suffix":""}],"badges":[],"createdAt":"2025-01-27 12:00:15","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-5912049/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-5912049/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1038/s41467-025-63708-4","type":"published","date":"2025-10-30T04:00:00+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":75405556,"identity":"1d27791a-6aa6-44a2-90a8-63435a1fabc8","added_by":"auto","created_at":"2025-02-04 08:47:36","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":209992,"visible":true,"origin":"","legend":"\u003cp\u003eSelected bright-field STEM images of pristine (a) PtAl(R) and (b) PtAl. Corresponding particle size distributions (c, d) using the Rice estimator for bin widths.\u003c/p\u003e","description":"","filename":"image1.png","url":"https://assets-eu.researchsquare.com/files/rs-5912049/v1/2bfb0e47c028481e81d396e0.png"},{"id":75405554,"identity":"4db09ae1-f982-423c-998c-26b371e99069","added_by":"auto","created_at":"2025-02-04 08:47:36","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":881311,"visible":true,"origin":"","legend":"\u003cp\u003e(a) XRD and (b) PDF patterns of PtAl(R) and of the Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e support and their difference. (c) XRD and (d) PDF patterns of PtAl and of the Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e support and their difference. Difference in (c) is magnified by a factor 3 for clarity. The main diffraction peaks and Pt-Pt correlations for fcc Pt are labeled in a) and b), respectively. Difference patterns are offset for clarity.\u003c/p\u003e","description":"","filename":"image2.png","url":"https://assets-eu.researchsquare.com/files/rs-5912049/v1/35645d2baa119779c4d3b708.png"},{"id":75405557,"identity":"f338cc22-e682-4a48-8856-73975d5e6396","added_by":"auto","created_at":"2025-02-04 08:47:36","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":877373,"visible":true,"origin":"","legend":"\u003cp\u003eTime-evolution of (a) XRD and (b) PDF patterns of PtAl during the isothermal reduction in H\u003csub\u003e2\u003c/sub\u003e/Ar flow at 150°C. Time evolution (yellow to blue) of difference (c) XRD and (d) PDF patterns obtained by subtracting the last pattern before H\u003csub\u003e2\u003c/sub\u003e was admitted. The entire process takes place in 40 seconds.\u003c/p\u003e","description":"","filename":"image3.png","url":"https://assets-eu.researchsquare.com/files/rs-5912049/v1/553ff6853df761f52ec0ba7f.png"},{"id":75405567,"identity":"c3e31945-aec5-4498-9221-815e56972109","added_by":"auto","created_at":"2025-02-04 08:47:36","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":214300,"visible":true,"origin":"","legend":"\u003cp\u003e(a) Kinetics of PtAl reduction in gas and liquid phase, determined from normalized intensity of the nearest-neighbor Pt-Pt peak at about R= 2.77 Å in the PDF patterns. (b) Difference PDF patterns (dots) of PtAl at the end of the isothermal reduction in H\u003csub\u003e2\u003c/sub\u003e/Ar flow at 150 °C (gas) and in H\u003csub\u003e2\u003c/sub\u003e-saturated cyclohexane at 70°C (liquid) and their fit (solid lines), compared to simulated PDF patterns of the Pt NPs in the Pt\u003csub\u003e55\u003c/sub\u003eH\u003csub\u003e91\u003c/sub\u003e/γ-Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e model reported in (a). Only the contribution from the Pt phase has been simulated. Patterns are offset for clarity.\u003c/p\u003e","description":"","filename":"image4.png","url":"https://assets-eu.researchsquare.com/files/rs-5912049/v1/40999e9eb74f5e4a7236bafa.png"},{"id":75405572,"identity":"3d10fa5d-08c2-46f5-aca4-009ca20b27c8","added_by":"auto","created_at":"2025-02-04 08:47:36","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":367445,"visible":true,"origin":"","legend":"\u003cp\u003e(a) Simulated PDF patterns of Pt\u003csub\u003e55\u003c/sub\u003eH\u003csub\u003e91\u003c/sub\u003e/Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e, Pt\u003csub\u003e55\u003c/sub\u003eH\u003csub\u003e44\u003c/sub\u003e/Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e and Pt\u003csub\u003e55\u003c/sub\u003e/Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e models and the difference with respect to Pt\u003csub\u003e55\u003c/sub\u003e/Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e (diff). (b) Pt\u003csub\u003e55\u003c/sub\u003eH\u003csub\u003e91\u003c/sub\u003e/Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e, Pt\u003csub\u003e55\u003c/sub\u003eH\u003csub\u003e44\u003c/sub\u003e/Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e and Pt\u003csub\u003e55\u003c/sub\u003e/Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e models. (c) Experimental PDF patterns of PtAl immediately after the isothermal reduction in H\u003csub\u003e2\u003c/sub\u003e/Ar at 150°C and after purging in Ar for 10 min and their difference. The box indicates the region fitted as described in panel (d). (d) Fitting procedure applied to a PDF pattern, corrected by a linear background subtraction, of PdAl collected during one ME cycle at 150°C. The experimental pattern is fit with three gaussian components.\u003c/p\u003e","description":"","filename":"image5.png","url":"https://assets-eu.researchsquare.com/files/rs-5912049/v1/d4587533dc68711dfd7409c7.png"},{"id":75407791,"identity":"3421b916-4cb6-498e-a730-95f3afa145cc","added_by":"auto","created_at":"2025-02-04 08:55:36","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":534245,"visible":true,"origin":"","legend":"\u003cp\u003eFit of the experimental PDF data of (a, b) PtAl and (c, d) PtAl(R) during 10 modulation cycles of H\u003csub\u003e2\u003c/sub\u003e/Ar at 150 °C. (a, c) Variation of the Pt-Pt distance in the first five cycles; (b, d) variation of FWHM of the Pt-Pt peak and of the amplitude of the (Pt-supp)\u003csub\u003elong\u003c/sub\u003e peak, averaged over the ten cycles. Fit results are reported as dots, while lines are obtained upon averaging 5 neighboring points.\u003c/p\u003e","description":"","filename":"image6.png","url":"https://assets-eu.researchsquare.com/files/rs-5912049/v1/a2815124f78569380411f3be.png"},{"id":75405564,"identity":"d81222e1-52b6-45c1-afd7-c942048f8f8d","added_by":"auto","created_at":"2025-02-04 08:47:36","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":996407,"visible":true,"origin":"","legend":"\u003cp\u003eFit of the experimental PDF data of (a, b) PtAl and (c, d) PtAl(R) during modulation 10 cycles of H\u003csub\u003e2\u003c/sub\u003e-saturated cyclohexane/Ar-saturated cyclohexane at 70 °C. (a, c) Variation of the Pt-Pt distance in the first five cycles; (b, d) variation of FWHM of the Pt-Pt peak and of the amplitude of the (Pt-supp)\u003csub\u003elong\u003c/sub\u003e peak, averaged over the ten cycles. Fit results are reported as dots, while lines are obtained upon averaging 5 neighboring points.\u003c/p\u003e","description":"","filename":"image7.png","url":"https://assets-eu.researchsquare.com/files/rs-5912049/v1/20621ce3abb191c85a5f085f.png"},{"id":94829185,"identity":"791a25a6-697f-4cb6-9cfc-c76006ebdf5e","added_by":"auto","created_at":"2025-10-31 07:06:32","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":3865328,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-5912049/v1/008c4fe4-e9da-41a1-9ce7-40e8514e99ef.pdf"},{"id":75405555,"identity":"978aec11-ab6f-4baa-819c-1acd54b1713e","added_by":"auto","created_at":"2025-02-04 08:47:36","extension":"docx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":3980703,"visible":true,"origin":"","legend":"Supporting Information","description":"","filename":"BonaviaESI250127.docx","url":"https://assets-eu.researchsquare.com/files/rs-5912049/v1/d277c47e565e33784a269cb5.docx"}],"financialInterests":"There is \u003cb\u003eNO\u003c/b\u003e Competing Interest.","formattedTitle":"Pt nanoparticles breathe and reversibly detach from Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e in hydrogen","fulltext":[{"header":"Introduction","content":"\u003cp\u003eSupported metal nanoparticles (NPs) are pivotal as heterogeneous catalysts in numerous industrial and environmental processes.\u003csup\u003e\u003cspan additionalcitationids=\"CR2 CR3 CR4 CR5\" citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e\u003c/sup\u003e Early research established structure-activity correlations\u003csup\u003e\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e\u003c/sup\u003e and rationalized the impact of NPs size on catalytic activity and selectivity.\u003csup\u003e\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e, \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e\u003c/sup\u003e Metal NPs are also active entities with their own dynamic behavior in the presence of adsorbates and/or under reaction conditions.\u003csup\u003e\u003cspan additionalcitationids=\"CR11 CR12\" citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e\u003c/sup\u003e Understanding the structural evolution of metal NPs in various reaction environments is crucial for precise control over their size and reactivity, both of which are essential for catalyst design, as well as for the regeneration of deactivated catalysts.\u003csup\u003e\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e, \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e\u003c/sup\u003e\u003c/p\u003e \u003cp\u003ePlatinum NPs are among the most studied catalytic systems. The CO-induced reconstruction of Pt surfaces and of Pt NPs is a classic example of adsorbate-induced surface reconstruction.\u003csup\u003e\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e, \u003cspan additionalcitationids=\"CR17 CR18 CR19 CR20\" citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e\u003c/sup\u003e Similarly, H\u003csub\u003e2\u003c/sub\u003e can induce electronic and morphological restructuring of supported Pt clusters.\u003csup\u003e\u003cspan additionalcitationids=\"CR23 CR24 CR25\" citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e\u003c/sup\u003e At room temperature and sub-ambient pressure, H\u003csub\u003e2\u003c/sub\u003e splits on Pt surfaces, forming various Pt hydrides. In nanoscale Pt particles, hydride formation is accompanied by structural reconstruction, as demonstrated by Mager-Maury et al.\u003csup\u003e\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e\u003c/sup\u003e using density functional theory (DFT) calculations on a model Pt\u003csub\u003e13\u003c/sub\u003e cluster supported on γ-Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e. Their findings revealed that, as the H/Pt ratio increases, the Pt\u003csub\u003e13\u003c/sub\u003e cluster transitions from a biplanar morphology, strongly interacting with the support, to a more symmetric cuboctahedral structure, which almost detaches from the support. Similar behavior was observed for Pt\u003csub\u003e37\u003c/sub\u003e clusters on graphene,\u003csup\u003e\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e\u003c/sup\u003e suggesting a universal nature of this process across diverse NP sizes and supports of very different nature.\u003c/p\u003e \u003cp\u003eThe available theoretical calculations for Pt clusters on γ-Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e27\u003c/sup\u003e propose three primary descriptors for this restructuring phenomenon as a function of the hydrogen partial pressure: i) changes in the relative amounts of linear and bridged Pt hydrides, ii) elongation of the average Pt-Pt distance (i.e. the \"breathing\" of the Pt NPs), and iii) increased Pt-support distance (i.e. the detachment of the Pt NPs). To date, only limited experimental evidence supports these theoretical predictions. As regards the amount of Pt hydrides, titration experiments found values of the H/Pt\u003csub\u003esurf\u003c/sub\u003e ratio greater than 1 for ultra-dispersed Pt NPs,\u003csup\u003e\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e, \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e\u003c/sup\u003e in good agreement with models where the Pt NPs are completely hydrogenated. Recently, we provided experimental evidence of the conversion of linear Pt hydrides into bridged species on 5 wt% Pt/Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e using Fourier transform infrared (FT-IR) spectroscopy and inelastic neutron scattering (INS) spectroscopy,\u003csup\u003e\u003cspan additionalcitationids=\"CR31\" citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e\u003c/sup\u003e in excellent agreement with the theoretical prediction.\u003csup\u003e\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e\u003c/sup\u003e With respect to structural descriptors, only the breathing of Pt NPs in the presence of H\u003csub\u003e2\u003c/sub\u003e was confirmed experimentally. X-ray absorption spectroscopy (XAS) showed a contracted \u003cem\u003efcc\u003c/em\u003e lattice\u003csup\u003e\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e\u003c/sup\u003e and higher structural disorder in naked Pt NPs compared to bulk Pt,\u003csup\u003e\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e, \u003cspan additionalcitationids=\"CR35 CR36\" citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e\u003c/sup\u003e while hydrogen adsorption induces lattice relaxation and more structural order (e.g. restoring of the \u003cem\u003efcc\u003c/em\u003e symmetry). In contrast, apart from the mobility of Pt clusters detected by environmental STEM under H\u003csub\u003e2\u003c/sub\u003e,\u003csup\u003e\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e\u003c/sup\u003e the direct observation of the H\u003csub\u003e2\u003c/sub\u003e-induced detachment of Pt NPs from the support remains elusive. This is due to the minute structural effects associated with NP detachment from the support, which to date have not been observed by either XAS or synchrotron X-ray pair distribution function (PDF) analysis,\u003csup\u003e\u003cspan additionalcitationids=\"CR40\" citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e41\u003c/span\u003e\u003c/sup\u003e despite the latter is able to describe the structural changes in 1\u0026ndash;3 nm sized Pt NPs on Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e induced by adsorbates from the gas phase.\u003csup\u003e\u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e42\u003c/span\u003e\u003c/sup\u003e Finally, the reversibility of the H\u003csub\u003e2\u003c/sub\u003e-induced restructuring and its dependence on the reaction environment are also unexplored yet critical areas, with practical implications for catalyst stability and performance under hydrogenation conditions.\u003c/p\u003e \u003cp\u003eTo capture experimentally all these dynamic aspects of NPs restructuring, we combined high-energy x-ray diffraction (XRD) and PDF analysis, in a modulated excitation experimental approach, to study two industrial Pt/Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e catalysts characterized by different particle size distributions, previously investigated by IR spectroscopy and INS.\u003csup\u003e\u003cspan additionalcitationids=\"CR31\" citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e, \u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e43\u003c/span\u003e\u003c/sup\u003e The experiments were designed to recreate the conditions in which NPs are expected to either be completely hydrogenated and (partially) detached from the support or, conversely, to strongly interact with the support. The combination of structure-sensitive techniques, experiment design and advanced data analysis allowed us to present conclusive evidence of the simultaneous H\u003csub\u003e2\u003c/sub\u003e-induced breathing and reversible (partial) detachment of Pt NPs in both gas and liquid environments. These findings provide experimental proof of the ductility of supported NPs in the presence of adsorbates in terms of particle reconstruction, opening up fascinating new perspectives on their catalytic behavior in various reaction environments.\u003c/p\u003e"},{"header":"Experimental details and data analysis","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003eCatalyst synthesis and preliminary characterization\u003c/h2\u003e \u003cp\u003eThe two 5 wt% Pt/Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e catalysts investigated in this work were prepared by Chimet S.p.A. (Viciomaggio, Italy), following a deposition-precipitation method\u003csup\u003e\u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e44\u003c/span\u003e\u003c/sup\u003e using a high-surface-area transitional alumina as a support (SSA\u0026thinsp;=\u0026thinsp;116 m\u003csup\u003e\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e\u003c/sup\u003e g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e; pore volume\u0026thinsp;=\u0026thinsp;0.41 cm\u003csup\u003e\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e\u003c/sup\u003e g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e; mixed phase). These two catalysts differ in whether or not a reduction step was performed after Pt deposition: one catalyst (hereafter called PtAl) was not pre-reduced and so the Pt phase is fully oxidized in the pristine sample; the other (hereafter PtAl(R)) was reduced using sodium formate as reducing agent, hence, the Pt phase is metallic, but passivated by a thin oxide layer. In both cases, after the synthesis the catalysts were thoroughly washed with water and then dried at 120\u0026deg;C overnight. The nominal Pt dispersion was determined by H\u003csub\u003e2\u003c/sub\u003e/O\u003csub\u003e2\u003c/sub\u003e titration\u003csup\u003e\u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e45\u003c/span\u003e\u003c/sup\u003e on samples reduced at 120\u0026deg;C, and was D\u0026thinsp;=\u0026thinsp;63%, and D\u0026thinsp;=\u0026thinsp;21% for PtAl and PtAl(R), respectively.\u003c/p\u003e \u003cp\u003eTransmission Electron Microscopy (STEM) imaging was performed using a probe-corrected JEOL JEM ARM-200 F (NeoARM) microscope equipped with a cold FEG gun operated at 200 keV. Scanning transmission electron microscopy (STEM) high-angle annular dark-field (HAADF) images were collected at 68 mrad\u0026thinsp;\u0026lt;\u0026thinsp;α\u0026thinsp;\u0026lt;\u0026thinsp;280 mrad. Approximately 800 particles were counted in the HAADF-STEM images of each sample in order to estimate the particle size distribution using the approach by Alxneit.\u003csup\u003e\u003cspan citationid=\"CR46\" class=\"CitationRef\"\u003e46\u003c/span\u003e\u003c/sup\u003e\u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003eIn-situ XRD measurements\u003c/h3\u003e\n\u003cp\u003eIn situ X-ray diffraction measurements were performed at beamline ID15A\u003csup\u003e\u003cspan citationid=\"CR47\" class=\"CitationRef\"\u003e47\u003c/span\u003e\u003c/sup\u003e at the ESRF synchrotron (Grenoble, France) using an X-ray beam energy of 98 keV (λ\u0026thinsp;=\u0026thinsp;0.1265 \u0026Aring;) and a photon-counting Pilatus3X 2M CdTe detector (Dectris, Switzerland) positioned at a 330 mm sample-to-detector distance. Beam size was 100\u0026times;100 \u0026micro;m\u003csup\u003e\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e\u003c/sup\u003e (vertical\u0026times;horizontal) and the average flux on the sample was 10\u003csup\u003e12\u003c/sup\u003e photons s\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e. A stainless-steel cell designed to feed the gas/liquid bottom-up through a 9 mm\u003csup\u003e\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e\u003c/sup\u003e catalyst bed provided leak-tight operation, minimal dead volume upon switching flows, low scattering background, and a wide exit angle for measurements enabling PDF analysis (see Supporting Information for details).\u003c/p\u003e \u003cp\u003eThe sample (approximately 30 mg) was placed in the cell between two quartz wool plugs used to both diffuse the gas/liquid feed and suppress sample movement. Throughout the following protocol, we collected scattering data continuously with a time resolution of 1 s/pattern. The sample was kept 1 min at ambient temperature under Ar (gas phase experiment) or Ar-saturated cyclohexane (liquid phase experiment). Then the temperature was increased at a rate of 10\u0026deg;C/min to 150\u0026deg;C (gas phase) or 70\u0026deg;C (liquid phase), under Ar (flow of 100 ml/min, gas phase) or Ar-saturated cyclohexane (1 ml/min, liquid phase). At this point, the gas flowing through the cell was changed to 5 vol% H\u003csub\u003e2\u003c/sub\u003e/Ar (gas phase) or to H\u003csub\u003e2\u003c/sub\u003e-saturated cyclohexane (liquid phase) to perform an isothermal reduction for 30 min. Lastly, the sample was washed in Ar (gas phase) or Ar-saturated cyclohexane (liquid phase) at the same temperature for 30 min. Modulated excitation experiments were started at this point by exposing the sample to repeated cycles of 5 vol% H\u003csub\u003e2\u003c/sub\u003e/Ar (10 min) and Ar (10 min) or H\u003csub\u003e2\u003c/sub\u003e-saturated cyclohexane (5 min) and Ar-saturated cyclohexane (5 min). Reference data such as blank Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e in different phases were collected in the same conditions.\u003c/p\u003e \u003cp\u003eThe use of a stainless steel valve and a ceramic valve (VICI AG, Switzerland) enabled repeated, no-dead time switching between the two different gas/liquid flows. Gas feeds were delivered through calibrated mass flow meters (Bronkhorst, Netherlands) and stainless steel tubing (1/16\u0026rsquo;\u0026rsquo;) while liquid feeds were circulated by a calibrated peristaltic pump (Spetec, Germany) installed upstream of the cell and Teflon and stainless steel tubing. Two glass bottles were used as reservoirs for cyclohexane solvent (HPLC purity, Sigma Aldrich) and were fitted with a frit to allow for saturation with pure gases (Ar or H\u003csub\u003e2\u003c/sub\u003e, both 99.999 vol%). Cyclohexane was selected as model solvent because it can be considered non-interacting with the catalyst and also in order to remain consistent with the previous study using IR spectroscopy to analyse Pt hydrides on these catalysts.\u003csup\u003e\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e\u003c/sup\u003e A quadrupole mass spectrometer (Hiden Analytical, UK) connected to the outlet of the cell was used to monitor gas feed and its evolution in the gas phase experiments.\u003c/p\u003e\n\u003ch3\u003eData reduction and PDF calculation\u003c/h3\u003e\n\u003cp\u003eTwo-dimensional X-ray scattering data were azimuthally integrated using pyFAI.\u003csup\u003e\u003cspan citationid=\"CR48\" class=\"CitationRef\"\u003e48\u003c/span\u003e\u003c/sup\u003e Data were corrected for the flat-field response and spatial distortion of the detector,\u003csup\u003e\u003cspan citationid=\"CR49\" class=\"CitationRef\"\u003e49\u003c/span\u003e\u003c/sup\u003e X-ray beam polarization, and variations in the incident photon flux. Azimuthally integrated data were converted to PDF using PDFgetx3,\u003csup\u003e\u003cspan citationid=\"CR50\" class=\"CitationRef\"\u003e50\u003c/span\u003e\u003c/sup\u003e using a range of momentum transfer 0.8\u0026thinsp;\u0026le;\u0026thinsp;Q\u0026thinsp;\u0026le;\u0026thinsp;22 \u0026Aring;\u003csup\u003e\u0026minus;1\u003c/sup\u003e and the scattering patterns of the empty cell and/or blank Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e support collected under identical conditions as background. This enabled isolating Pt-Pt correlations related to the NPs from interatomic correlations involving the support.\u003c/p\u003e\n\u003ch3\u003eData fitting and simulation\u003c/h3\u003e\n\u003cp\u003eStructural models were fitted to XRD powder patterns and PDF data using Topas v7.\u003csup\u003e\u003cspan citationid=\"CR51\" class=\"CitationRef\"\u003e51\u003c/span\u003e\u003c/sup\u003e Crystallite size was estimated either from fits to PDF data using a spherical-particle dampening model or from fitting high-resolution XRD data, collected at the ID22 beamline at the ESRF (see Supporting Information for details).\u003csup\u003e\u003cspan citationid=\"CR52\" class=\"CitationRef\"\u003e52\u003c/span\u003e\u003c/sup\u003e\u003c/p\u003e \u003cp\u003eWith the exception of the pristine PtAl sample (see below), the PDF data were fitted by Gaussian peaks corresponding to Pt-Pt distances in the Pt \u003cem\u003efcc\u003c/em\u003e structure, using lmfit.\u003csup\u003e\u003cspan citationid=\"CR53\" class=\"CitationRef\"\u003e53\u003c/span\u003e\u003c/sup\u003e Additionally, they were compared to a set of calculated PDFs corresponding to a series of Pt\u003csub\u003ex\u003c/sub\u003eH\u003csub\u003ey\u003c/sub\u003e/γ-Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e models, consisting of Pt\u003csub\u003ex\u003c/sub\u003eH\u003csub\u003ey\u003c/sub\u003e nanoparticles of various sizes (x\u0026thinsp;=\u0026thinsp;13, 34, 55) and hydrogen coverages supported on a slab of dehydroxylated γ-Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e(100) surface. Notably, the local structure of γ-Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e is indistinguishable from that of the other alumina phases (Figure S2c). The most stable structures of the Pt\u003csub\u003e13\u003c/sub\u003eH\u003csub\u003ey\u003c/sub\u003e/γ-Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e models were obtained previously by using DFT calculations based on velocity scale molecular dynamics followed by a quenching procedure,\u003csup\u003e\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e\u003c/sup\u003e while the larger models (x\u0026thinsp;=\u0026thinsp;34 and x\u0026thinsp;=\u0026thinsp;55) were obtained by static optimization because of computational cost. The Pt\u003csub\u003e34\u003c/sub\u003eH\u003csub\u003e54\u003c/sub\u003e/γ-Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e, Pt\u003csub\u003e55\u003c/sub\u003eH\u003csub\u003e44\u003c/sub\u003e/γ-Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e and Pt\u003csub\u003e55\u003c/sub\u003eH\u003csub\u003e91\u003c/sub\u003e/γ-Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e structures were adopted previously to explain the behavior of supported Pt NPs in the same PtAl sample in different hydrogenation conditions,\u003csup\u003e\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e\u003c/sup\u003e while the naked Pt\u003csub\u003e34\u003c/sub\u003e/γ-Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e and Pt\u003csub\u003e55\u003c/sub\u003e/γ-Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e systems were constructed as detailed in Supporting information. The selected sizes of the Pt clusters, which correspond to about 1 nm (Pt\u003csub\u003e13\u003c/sub\u003e) to 1.5 nm (Pt\u003csub\u003e55\u003c/sub\u003e), represent the best compromise between the range of STEM sizes and the limitations imposed by computational costs. Total and partial PDFs of the Pt\u003csub\u003ex\u003c/sub\u003eH\u003csub\u003ey\u003c/sub\u003e/γ-Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e models were calculated over the same range of Q used for the experimental PDF data using DebyeCalculator.\u003csup\u003e\u003cspan citationid=\"CR54\" class=\"CitationRef\"\u003e54\u003c/span\u003e\u003c/sup\u003e\u003c/p\u003e"},{"header":"Results and discussion","content":"\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003eCharacterization of the pristine catalysts\u003c/h2\u003e \u003cp\u003eThe two Pt/Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e catalysts show similar homogeneous distribution of Pt NPs but different average NP size (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). The pre-reduced sample, PtAl(R), displays a log-normal distribution with a mode around 3.0 nm (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ea-c), while PtAl has smaller particles, with a bimodal distribution peaking at about 1.0 nm and 2.2 nm (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eb-d). Both distributions are narrow enough to ensure reliable XRD and PDF analysis.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe XRD patterns of the catalysts (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ea and Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ec) are dominated by the peaks of the Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e support, which consists of a mixture of the \u0026trade;- and θ-phases with a minor contribution from γ-Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e (see Figure S2 in Supporting Information for details). To isolate the contribution of Pt in the patterns of PtAl and PtAl(R), the data of the same Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e support used to prepare the two catalysts was subtracted from those of the two catalysts. The difference pattern of PtAl(R) (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ea) exhibits clear diffraction peaks of face-centered cubic (\u003cem\u003efcc\u003c/em\u003e) Pt. An average crystallite size of 2.8 nm was estimated based on the XRD peak widths (Table \u003cspan refid=\"MOESM1\" class=\"InternalRef\"\u003eS1\u003c/span\u003e). In contrast, the difference pattern of PtAl (c) shows broader, weaker peaks (ca. 2.6 and 4.0 \u0026Aring;\u003csup\u003e\u0026minus;1\u003c/sup\u003e), which can be attributed to an oxidized phase,\u003csup\u003e\u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e, \u003cspan citationid=\"CR55\" class=\"CitationRef\"\u003e55\u003c/span\u003e\u003c/sup\u003e in line with previous measurements on the same sample\u003csup\u003e\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e\u003c/sup\u003e and with observations of well-dispersed metal hydroxide in catalysts prepared by deposition-precipitation reported in the literature.\u003csup\u003e\u003cspan additionalcitationids=\"CR57 CR58\" citationid=\"CR56\" class=\"CitationRef\"\u003e56\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR59\" class=\"CitationRef\"\u003e59\u003c/span\u003e\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eFigure \u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eb and Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ed compare the PDF curves of both catalysts to that of the Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e support. Figure S3 shows the same data in a wider R range, along with the fit used to estimate the NPs size. After background subtraction, the difference PDF reflects only interatomic distances within the Pt NPs. For PtAl(R) (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eb), the most intense peaks appear at ca. 2.76, 4.79 and 7.32 \u0026Aring;, corresponding to the 1st, 3rd and 7th shell Pt-Pt distances in the \u003cem\u003efcc\u003c/em\u003e Pt phase (i.e. those with the highest multiplicity). The intensity falloff as a function of R can be modeled using a spherical particle diameter of 3.3 nm (Table \u003cspan refid=\"MOESM1\" class=\"InternalRef\"\u003eS1\u003c/span\u003e), in agreement with the estimate from XRD and consistent with the particle size estimated from STEM. The difference PDF of PtAl contains only a few clearly discernible peaks up to 6 \u0026Aring; (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ed), among which the peak at about 2.0 \u0026Aring; is typical of Pt-O distances in Pt oxide/hydroxide.\u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003eIsothermal reduction in gas and liquid phase\u003c/h3\u003e\n\u003cp\u003eThe reduction of the catalysts was performed in H\u003csub\u003e2\u003c/sub\u003e under isothermal conditions in both gas phase (H\u003csub\u003e2\u003c/sub\u003e/Ar, 150\u0026deg;C) and liquid phase (H\u003csub\u003e2\u003c/sub\u003e-saturated cyclohexane, 70\u0026deg;C). No changes were observed for PtAl(R) (Figure S4-S5 and Table \u003cspan refid=\"MOESM1\" class=\"InternalRef\"\u003eS1\u003c/span\u003e), confirming that the Pt phase was already reduced and a possible oxide passivation layer was undetectable. In contrast, the reduction of the Pt-oxide phase was clearly observed for PtAl, in both gas (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e) and liquid phases (Figure S6). Difference patterns (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ec and Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ed) highlight the relatively small changes to the XRD patterns during reduction in H\u003csub\u003e2\u003c/sub\u003e/Ar at 150\u0026deg;C.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eBoth XRD and PDF data show that the Pt-oxide phase is gradually reduced to metallic \u003cem\u003efcc\u003c/em\u003e Pt by H\u003csub\u003e2\u003c/sub\u003e. Difference XRD (c) shows broad negative peaks at the positions assigned to PtO\u003csub\u003e2\u003c/sub\u003e (around 2.6 and 4.0 \u0026Aring;\u003csup\u003e\u0026minus;1\u003c/sup\u003e), which pinpoint its disappearance. Positive peaks appear at positions characteristic for metallic Pt (2.8, 3.2, 4.5, 5.3 and 7.0 \u0026Aring;\u003csup\u003e\u0026minus;1\u003c/sup\u003e). In the PDF (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ed), the sharp peaks corresponding to the 1st, 3rd, and 7th shell Pt-Pt distances emerged clearly during reduction. From the temporal evolution of their normalized intensity, we obtained kinetic information on the Pt oxide reduction (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ea): reduction by H\u003csub\u003e2\u003c/sub\u003e in the gas phase was completed within 10 s, while it was almost ten times slower in the liquid phase. We attribute this difference to a combination of factors: the higher reduction temperature in the gas phase experiment (150\u0026deg;C vs. 70\u0026deg;C, the latter imposed by the boiling point of the solvent), the poor solubility and the lower diffusivity of H\u003csub\u003e2\u003c/sub\u003e in cyclohexane, resulting in lower H\u003csub\u003e2\u003c/sub\u003e concentration in the liquid-phase experiment.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eAt the end of the reduction process, and in excess of H\u003csub\u003e2\u003c/sub\u003e, the Pt phases in PtAl were identical regardless of the reaction environment and temperature (dotted lines in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eb). Fits to the background-subtracted PDFs (solid lines in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eb) returned very similar lattice parameters and a NP size of 2.3\u0026thinsp;\u0026plusmn;\u0026thinsp;0.1 nm after both liquid and gas-phase reductions (Table \u003cspan refid=\"MOESM1\" class=\"InternalRef\"\u003eS1\u003c/span\u003e). This provides compelling evidence that the Pt oxide phase in PtAl is completely reduced in cyclohexane also at 70\u0026deg;C, and that the reaction environment does not affect Pt particle size, which remains very close to the center of the distribution evaluated by STEM on the pristine (unreduced) PtAl catalyst (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). The same applies also to PtAl(R) (Figure S7), although the average NP size remains far larger than in the reduced PtAl (Table \u003cspan refid=\"MOESM1\" class=\"InternalRef\"\u003eS1\u003c/span\u003e). The PDF patterns of the reduced catalysts (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eb), where the short-range order is largely dictated by bulk \u003cem\u003efcc\u003c/em\u003e Pt, are well reproduced by the highly symmetric Pt\u003csub\u003ex\u003c/sub\u003eH\u003csub\u003ey\u003c/sub\u003e/Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e cuboctahedral models from DFT calculations,\u003csup\u003e\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e\u003c/sup\u003e in which the Pt NPs are surrounded by hydrogen and detached from the alumina support (Pt\u003csub\u003e55\u003c/sub\u003eH\u003csub\u003e91\u003c/sub\u003e/Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e). The choice of hydrogenated Pt NPs models is justified by the experimental evidence from IR spectroscopy in both the gas and the liquid phase\u003csup\u003e\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e, \u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e\u003c/sup\u003e and INS in gas phase\u003csup\u003e\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e\u003c/sup\u003e that, under very similar experimental conditions, various surface Pt hydride species exist on these catalysts.\u003c/p\u003e \u003cp\u003e \u003cb\u003ePt NPs breathe and detach from the support in the presence of H\u003c/b\u003e \u003csub\u003e \u003cb\u003e2\u003c/b\u003e \u003c/sub\u003e: \u003cb\u003edirect structural evidence\u003c/b\u003e\u003c/p\u003e \u003cp\u003eHydrides are unstable in the absence of H\u003csub\u003e2\u003c/sub\u003e and are decomposed once the surrounding is changed to Ar after reduction; as a consequence, the Pt NPs undergo surface relaxation accompanied by disordering. Figure\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ea compares the simulated PDF for a supported Pt\u003csub\u003e55\u003c/sub\u003e NP dehydrogenated and in two different hydrogenation states. Supported Pt\u003csub\u003e34\u003c/sub\u003e and Pt\u003csub\u003e13\u003c/sub\u003e NPs behave very similarly (Figure S8). In the high H-coverage regime (Pt\u003csub\u003e55\u003c/sub\u003eH\u003csub\u003e91\u003c/sub\u003e/Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e, Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003eb), the simulated PDF peaks are sharp and largely determined by the Pt fcc structure. In the naked state (Pt\u003csub\u003e55\u003c/sub\u003e/Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e, Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ec), the Pt NP adopts an irregular morphology, strongly interacting with the alumina support. Correspondingly, the simulated PDF shows a more contracted first shell Pt-Pt peak compared to the hydrogenated counterpart, and completely smeared-out higher-shell Pt-Pt peaks. In an intermediate hydrogenation state (Pt\u003csub\u003e55\u003c/sub\u003eH\u003csub\u003e44\u003c/sub\u003e/Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e) the simulated PDF is intermediate. This effect is more pronounced upon decreasing the Pt particle size (Figure S8).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe experimental PDF patterns of PtAl in the fully hydrogenated (i.e. under H\u003csub\u003e2\u003c/sub\u003e/Ar at 150\u0026deg;C) and dehydrogenated (i.e. under Ar at 150\u0026deg;C) states (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ec) suggest that analogue changes indeed occur to the Pt NPs during dehydrogenation. The difference PDF (diff in Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ec) reveals a contraction of the first Pt-Pt distance of about 0.9% and a higher dispersion of the 3rd and 5th shell Pt-Pt peaks, closely resembling the simulated difference pattern for a Pt\u003csub\u003e55\u003c/sub\u003e NP (diff in Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ea). The contraction of the first shell Pt-Pt distance upon removal of H\u003csub\u003e2\u003c/sub\u003e can be interpreted as the breathing of the Pt NP induced by removal of hydride species, as well as the more irregular morphology responsible for the disappearance of the higher-shell Pt-Pt peaks.\u003c/p\u003e \u003cp\u003eTo provide also kinetic information and to emphasize structural changes with increased sensitivity, we performed a series of experiments after the isothermal reduction adopting the modulated excitation (ME) approach.\u003csup\u003e\u003cspan citationid=\"CR60\" class=\"CitationRef\"\u003e60\u003c/span\u003e, \u003cspan citationid=\"CR61\" class=\"CitationRef\"\u003e61\u003c/span\u003e\u003c/sup\u003e The raw (i.e. not Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e background subtracted) PDF data calculated from the XRD patterns collected during the ME experiment were analyzed to track the breathing of the Pt NPs in the presence/absence of H\u003csub\u003e2\u003c/sub\u003e, and their interaction with the support. In this latter case, difficulties arise because only very small changes can be expected to affect the Pt-support distances (less than 0.2 \u0026Aring;).\u003csup\u003e\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e\u003c/sup\u003e\u003c/p\u003e \u003cp\u003eWe focused on the region 2.5\u0026ndash;3.75 \u0026Aring; range of the PDF (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ed), which consists mostly of two peaks: the peak at 2.76 \u0026Aring; is dominated by the 1st shell Pt-Pt correlation, while that at 3.33 \u0026Aring; is mainly represented by Al-Al correlations from the Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e support (Figure S9). It is worth noticing that the intensity of the latter is negligible in the simulated PDF patterns of Pt\u003csub\u003e55\u003c/sub\u003eH\u003csub\u003ex\u003c/sub\u003e/Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ea) because the models comprise only a thin slab of Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e. Both peaks also contain information on Pt-support correlations: short and very heterogeneous Pt-support contributions, (Pt-supp)\u003csub\u003eshort\u003c/sub\u003e, predominate for Pt NPs in strong interaction with the support (Figure S10a), while longer Pt-support distances are found above 3.2 \u0026Aring; for hydrogenated NPs, (Pt-supp)\u003csub\u003elong\u003c/sub\u003e (Figure S10b). Attempts to fit the data in the 2.5\u0026ndash;3.75 \u0026Aring; range with four components (Pt-Pt\u0026thinsp;+\u0026thinsp;Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e +(Pt-supp)\u003csub\u003eshort\u003c/sub\u003e + (Pt-supp)\u003csub\u003elong\u003c/sub\u003e) were unstable, especially due to the strong parameter correlation between the Pt-Pt and (Pt-supp)\u003csub\u003eshort\u003c/sub\u003e contributions. Therefore, we used three gaussian contributions (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ee). The position of the first peak (blue) accounts for the first shell Pt-Pt distance; its full width at half maximum (FWHM) indicates the relative importance of the (Pt-supp)\u003csub\u003eshort\u003c/sub\u003e contribution, i.e. the larger the FWHM, the larger the (Pt-supp)\u003csub\u003eshort\u003c/sub\u003e contribution. The second gaussian contribution (grey) accounts for the Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e support and its parameters were fixed during the fit to the values obtained fitting the pattern of blank Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e. The amplitude of the third contribution (violet) estimates the relative weight of the (Pt-supp)\u003csub\u003elong\u003c/sub\u003e contribution, i.e. the different degree of interaction between the Pt NP and the Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e support.\u003c/p\u003e \u003cp\u003eIn the gas phase experiment at 150\u0026deg;C, the first shell Pt-Pt distance of PtAl equals that of bulk Pt (2.774 \u0026Aring;) at the end of the reduction step (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003ea). This distance contracts in the absence of hydrogen by ca. 0.7\u0026thinsp;\u0026plusmn;\u0026thinsp;0.1% with respect to the hydrogenated situation and expands in its presence by the same amount, in a reproducible and reversible way over the ten modulation cycles. It is worth noticing that during the half cycles without H\u003csub\u003e2\u003c/sub\u003e the Pt-Pt distance does not decrease to its H\u003csub\u003e2\u003c/sub\u003e-equilibrated value, indicating that the 10-min Ar flushing phase is insufficient to completely remove the Pt hydride species. For PtAl(R) in H\u003csub\u003e2\u003c/sub\u003e (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003ec), the Pt-Pt distance is slightly expanded with respect to the bulk. It behaves similarly to PtAl during dehydrogenation, but with a smaller perturbation of the Pt-Pt bond (0.2\u0026thinsp;\u0026plusmn;\u0026thinsp;0.1%), as expected from its larger, less ductile NPs. The NP breathing in both catalysts is not very pronounced but can be followed very precisely by these PDF data.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eVariations of the FWHM of the first gaussian contribution and of the amplitude of the (Pt-supp)\u003csub\u003elong\u003c/sub\u003e contribution are smaller than those of the Pt-Pt distance. To increase the signal-to-noise ratio, we report the variations of these two parameters after averaging data over ten cycles for PtAl in Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003eb and for PtAl(R) in Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003ed. For PtAl, the FWHM of the first peak increases by ca. 7\u0026thinsp;\u0026plusmn;\u0026thinsp;1% of its original value upon H\u003csub\u003e2\u003c/sub\u003e removal, revealing that the (Pt-supp)\u003csub\u003eshort\u003c/sub\u003e contribution becomes relevant in the inert (Ar) environment when hydrides are removed. Simultaneously, the amplitude of the (Pt-supp)\u003csub\u003elong\u003c/sub\u003e contribution decreases by 23\u0026thinsp;\u0026plusmn;\u0026thinsp;1%. Therefore, the inert atmosphere promotes the decomposition of hydride species and the interaction of the NP with the support. While statistically relevant, the smaller variations of all three parameters for PtAl(R) are attributed to the larger particles in this sample, which are less prone to detachment from the support. Taken together, these two observations provide experimental evidence that upon variation of hydrogen coverage, Pt NPs not only breathe but also move relative to the support. The distance from the support increases in the presence of H\u003csub\u003e2\u003c/sub\u003e and hydride species, and decreases when hydrides are removed.\u003c/p\u003e \u003cp\u003eSimilar behavior is observed in the liquid environment (Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e), but both breathing and movement relative to the support are less pronounced and kinetically slower than in the gas phase. The low H\u003csub\u003e2\u003c/sub\u003e concentration in the liquid phase and competition between H\u003csub\u003e2\u003c/sub\u003e and the solvent for adsorption sites at the Pt surface may both contribute to this. However, the behavior can be still captured precisely by the ME experiment: the Pt-Pt distance of NPs in PtAl changes by 0.3\u0026thinsp;\u0026plusmn;\u0026thinsp;0.1% and the amplitude of (Pt-supp)\u003csub\u003elong\u003c/sub\u003e by 3\u0026thinsp;\u0026plusmn;\u0026thinsp;1%. Observation of similar phenomena in the presence of a solvent and in the gas phase indicates that the structural / morphological reconstruction is a general feature of Pt NPs.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eOur data demonstrate that supported Pt NPs subjected to a reversible hydrogenation change their structure and distance from the support. As hydrogenated Pt NPs interact less strongly with the Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e support, they might become more available for interaction with adsorbates, including substrates to be hydrogenated. This has implications for a better understanding and control of the sustained stability of hydrogenation catalysts, since the detachment of the Pt NPs from the Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e support seems to be facilitated by hydrogen adsorption and could be a first step towards their mobility and leaching from the support, especially in liquid phase. The reproducibility of the modulation cycles in both gas and liquid phase, however, indicates that this must be a slow process under these experimental conditions and compared to the time scale of the ME experiments.\u003c/p\u003e"},{"header":"Conclusions","content":"\u003cp\u003eIn this study, we provide experimental evidence of the simultaneous H\u003csub\u003e2\u003c/sub\u003e-induced breathing and movement of well-dispersed Pt nanoparticles (NPs) relative to their alumina support. Both phenomena, previously predicted only by theoretical models, were captured directly with unprecedented accuracy using high-energy XRD and total scattering PDF techniques, combined with a concentration modulation experimental approach and an experimental design aimed at reproducing conditions where Pt NPs are either completely hydrogenated or bare. Our findings reveal that both phenomena occur in both gas- and liquid-phase environments and with a magnitude highly correlated with the size of the NPs. Remarkably, the process is fully reversible over the time scale of our experiment, demonstrating the stability of the catalyst towards further mobility or even leaching.\u003c/p\u003e \u003cp\u003eA better understanding of the dynamic behavior of metal NPs in the presence of adsorbates may open exciting opportunities for their rational control under reaction conditions. In this respect, our work not only validates the possibilities suggested by theoretical predictions, but also sets a new benchmark for experimental studies in the field of heterogeneous catalysis with supported metal NPs. It introduces a methodological approach to accurately track modifications at the metal-support interface in gas and liquid environments, where catalysis often occurs.\u003c/p\u003e"},{"header":"Declarations","content":"\u003ch2\u003eAcknowledgments\u003c/h2\u003e \u003cp\u003eD.B., S.C., E.G. and D.F. acknowledge financial support from ESRF and PSI. All authors acknowledge the ESRF for providing beamtime through proposals CH-6371 and IH-CH-1722 (\u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.15151/ESRF-ES-1025993103\u003c/span\u003e\u003cspan address=\"10.15151/ESRF-ES-1025993103\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e; \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.15151/ESRF-ES-1267577360\u003c/span\u003e\u003cspan address=\"10.15151/ESRF-ES-1267577360\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e). D.B. and S.C. thank the Partnership for Soft Condensed Matter (Grenoble, France) for supporting preparation of the experiments. S.C. acknowledges the technical assistance of D. Duran, E. Papillon, Y. Watier (ESRF) and A.R. Quirk (ILL, Grenoble, France). A.R., P.L. and E.G. acknowledge support from Project CH4.0 under the MUR program \u0026ldquo;Dipartimenti di Eccellenza 2023\u0026ndash;2027\u0026Prime; (CUP D13C22003520001).\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eBoudart M (1969) Catalysis by Supported Metals. In: Eley DD, Pines H, Weisz PB (eds) Advances in Catalysis. Academic\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBoudart M (1985) Heterogeneous catalysis by metals. J Mol Catal 30:27\u0026ndash;38\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eFarrauto RJ, Heck RM (1999) Catalytic converters: state of the art and perspectives. Catal Today 51:351\u0026ndash;360\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eChen A, Holt-Hindle P (2010) Platinum-Based Nanostructured Materials: Synthesis, Properties, and Applications. 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Angew Chem Int Ed 53:8890\u0026ndash;8894\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":true,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"nature-portfolio","isNatureJournal":true,"hasQc":false,"allowDirectSubmit":false,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"","title":"Nature Portfolio","twitterHandle":"","acdcEnabled":false,"dfaEnabled":false,"editorialSystem":"ejp","reportingPortfolio":"","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"","lastPublishedDoi":"10.21203/rs.3.rs-5912049/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-5912049/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThe dynamic behavior of supported metal nanoparticles under reaction conditions is a key factor in their catalytic performance. Pt nanoparticles are particularly susceptible to structural relaxation and disordering induced by adsorbed CO and H\u003csub\u003e2\u003c/sub\u003e. In a hydrogenated state, theoretical models have predicted not only the reshaping of Pt nanoparticles, but also their shift away from the surface of their metal oxide support. In this work we examined the dynamic behavior of well-dispersed 1\u0026ndash;3 nm diameter Pt nanoparticles under hydrogenation conditions. Using time-resolved X-ray diffraction and pair distribution function analysis allied to a modulated-excitation approach, we provide direct experimental evidence of the simultaneous \u0026ldquo;breathing\u0026rdquo; of the Pt nanoparticles and their detachment from the Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e support under H\u003csub\u003e2\u003c/sub\u003e atmosphere. These dynamic structural changes are shown to be size-dependent, to occur in both gas phase (150\u0026deg;C) and liquid phase (cyclohexane, 70\u0026deg;C), and to be reversible, thus ensuring the stability of the catalyst under hydrogenation conditions. Gaining direct structural evidence of the ductile behavior of supported metal nanoparticles in reactive chemical environments is a groundbreaking step towards precise structural control of catalysts under reaction conditions.\u003c/p\u003e","manuscriptTitle":"Pt nanoparticles breathe and reversibly detach from Al2O3 in hydrogen","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-02-04 08:47:31","doi":"10.21203/rs.3.rs-5912049/v1","editorialEvents":[],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"nature-communications","isNatureJournal":true,"hasQc":false,"allowDirectSubmit":false,"externalIdentity":"NCOMMS","sideBox":"Learn more about [Nature Communications](http://www.nature.com/ncomms/)","snPcode":"","submissionUrl":"https://mts-ncomms.nature.com/","title":"Nature Communications","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"ejp","reportingPortfolio":"Nature Communications","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"30bb7f29-255b-4660-8f70-eca3dda7f168","owner":[],"postedDate":"February 4th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[{"id":43742207,"name":"Physical sciences/Chemistry/Catalysis/Heterogeneous catalysis"},{"id":43742208,"name":"Physical sciences/Materials science/Nanoscale materials/Nanoparticles"}],"tags":[],"updatedAt":"2025-10-31T07:06:24+00:00","versionOfRecord":{"articleIdentity":"rs-5912049","link":"https://doi.org/10.1038/s41467-025-63708-4","journal":{"identity":"nature-communications","isVorOnly":false,"title":"Nature Communications"},"publishedOn":"2025-10-30 04:00:00","publishedOnDateReadable":"October 30th, 2025"},"versionCreatedAt":"2025-02-04 08:47:31","video":"","vorDoi":"10.1038/s41467-025-63708-4","vorDoiUrl":"https://doi.org/10.1038/s41467-025-63708-4","workflowStages":[]},"version":"v1","identity":"rs-5912049","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-5912049","identity":"rs-5912049","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}