Efficient Ammonia Production from Nitric Oxide under Real Condition Using Photo-Modulated Cu Single-Atom Catalysts

Efficient Ammonia Production from Nitric Oxide under Real Condition Using Photo-Modulated Cu Single-Atom Catalysts | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Article Efficient Ammonia Production from Nitric Oxide under Real Condition Using Photo-Modulated Cu Single-Atom Catalysts Jun Lu, Xiaoyan Liu, Zhuyu Luo, Shan Hu, Wanqi Tang, He Linfeng, and 8 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-8346707/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Efficient electrochemical reduction of nitric oxide (NORR) under practical low-concentration conditions remains challenging due to insufficient NO adsorption, sluggish proton-coupled electron transfer, and severe competition from hydrogen evolution. In this work, a photo-modulated electrocatalysis system was fabricated for driving the reduction of low concentration NO pollutant to NH 3 , based on Cu single atoms (Cu SAs) decorated MoS 2 . The light irradiation induces the Cu SAs active sites switched to a lower valence state with prolonged Cu−S bonds instantaneously, facilitating the adsorption and activation towards NO molecules even at low concentration. As anticipated, a high NH 3 yield up to 3228 µmol h − 1 mg − 1 with a Faradaic efficiency (FE) of 86.53% were achieved in a flow cell at a current density of 100 mA cm − 2 . Such NH 3 yield value and FE are much higher than that obtained by the electrocatalysis of NO reduction reaction (NORR) so far. This work demonstrates that rational modulation of the localized coordination structure of single-atom centers can unlock previously inaccessible activity for disposing low-concentration nitrogen-containing pollutants. Physical sciences/Chemistry/Environmental chemistry Physical sciences/Chemistry/Catalysis/Electrocatalysis Cu single atoms photo modulated electrocatalysis NO removal NO reduction NH3 synthesis Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Introduction Excessive anthropogenic emissions of nitric oxide (NO) as a major pollutant urgently demand an economical removal strategy 1 , 2 due to its environmental hazards (e.g., photochemical smog, ozone layer depletion, and acid rain). 3 , 4 Traditional selective catalytic reduction (SCR) technology for NO removal operating at high temperature with external reductant (NH 3 ) and thus requiring invest substantial capital investment and utilization of pressure-equipment, which is not cost-efficient 5 , 6 . Thus, renewable clean-energy-driven electro catalysis (EC) of NO reduction (NORR) to ammonia (NH 3 ) has attracted great interest as one of alternative approaches. This process utilizes electric derived from clean energy and the reaction occurs in aqueous solution, making it safe and environmentally friendly 7 . Notably, the actual NO concentration in exhaust gases is quite low, and its solubility in aqueous solution is also limited 8 – 10 . This makes direct electro-reduction and meantime achieving high-yield performance in continues flow cell a great challenge 11 , 12 . Moreover, the NORR process involves multiple proton-coupled electron transfer process, suffering from complex intermediates and byproducts, which often leads to low yield and uncontrollable selectivity 13 – 15 . Critical challenge lies in efficiently adsorbing and activating NO molecules at low concentrations, where enhanced NO affinity and effective suppression of the competing hydrogen evolution reaction (HER) are required. At higher current densities, overpotential-induced losses and mass-transport limitations further reduce the Faradaic efficiency (FE), complicating practical applications 16 . Efforts at early years have been devoted for selecting electrocatalysts at concentrated NO 17 . Among them, inexpensive Cu is proved to be one of the effective candidates owing to its apex location on NORR catalytic volcano plot by theoretical calculation 18 , 19 . A high NH 3 yield and FE were achieved by Cu foam at high NO concentration of 99.5% with overpotential up to -0.9 V (versus reversible hydrogen electrode, vs. RHE). With excellent intrinsic catalytic behavior of Cu, including crystal engineering (Cu(111) nanosheets) 20 , metal alloying (CuNi@BCN) 21 , construction of nanocomposites (S-Cu@Co/C) 22 and Cu single atoms (Cu SAs) 23 , various studies have been conducted for pursuing high NH 3 yield and FE 18 . However, when the concentration moved to real condition, the FE of Cu are dropping to below 10% 24 . Intuitively, lowering the NO concentration reduces the frequency of reactant-catalyst encounters. Strategies such as carbon-supported Cu nanoparticles and Co-Ru dual-site catalysts have been proposed to accelerate three-phase mass transport and reaction kinetics, thereby partially mitigating this limitation 25 – 27 . While these approaches enhance accessibility to active sites, they primarily address structural or transport-related bottlenecks. Besides structure evolution by exposing more active sites, focusing on modification on the intrinsic electronic characteristics of Cu, determine the adsorption energy and kinetics and directly affect FE and current density 28 , 29 . Nevertheless, these geometric modifications fail to rectify the intrinsic inertness of the catalytic center towards trace-level reactants. Merely increasing the number of sites is insufficient; the fundamental electronic propensity of the active site to capture and activate low-abundance NO must be radically enhanced. In this work, we focus on dynamic orbital engineering via a photo-modulated electrocatalysis (PMEC) system to surmount these intrinsic limitations in trade-offs of NORR. The catalyst, consisting of atomically dispersed Cu single atoms anchored on MoS 2 nanosheets (Cu SAs@MoS 2 ), demonstrates markedly enhanced NORR activity. Under illumination, light acts as a remote “switch” to manipulate the local coordination environment, and the redesigned Cu−S bonds undergo electronic and geometric perturbations that strengthen NO adsorption and substantially facilitate the protonation of the *NO intermediate, thereby accelerating the overall reaction kinetics. When orchestrated in a continuous-flow reactor, the Cu SAs@MoS₂ catalyst delivers an NH 3 production rate of 3228 µmol cm − 2 h − 1 and FE of 86.53% at 100 mA cm − 2 under 10 vol% NO, representing the highest performance reported for NORR and setting a new benchmark for NORR under dilute conditions. This work demonstrates dynamic modulation on Cu−S bonds and interactions between reactants can be harnessed to overcome fundamental limitations of low-concentration small-molecule adsorption, suggesting that dynamic modulation of the coordination sphere is a potent avenue for catalyzing low-concentration reactions. Results Synthesis and characterizations As illustrated in Fig. 1 a, Cu SAs@MoS 2 material was synthesized by a microwave-assisted hydrothermal method using uniformly dispersed copper nanowires (Cu NWs), Mo 2 O 24 6− , and thiourea as copper, molybdenum and sulfide sources, respectively. In the initial stage, MoS 2 grew on the surface of Cu NWs, forming a one dimensional wormlike morphology. During the continuous microwave heating process, copper nanowires gradually dissolve and re-precipitate on the preformed MoS 2 substrate at single atom states in the later stage. The scanning electron microscope (SEM) image clearly demonstrates that the wormlike Cu SAs@MoS 2 is assembled by MoS 2 nanosheets (Supplementary Fig. S1 a). Without the addition of Cu NWs, pure MoS 2 with a spherical morphology was also synthesized by the same hydrothermal synthesis method as a reference sample (Supplementary Figs. S2 and S3). The difference in morphology between these two materials indicate that the copper nanowires served as morphology regulating template in the early stage. The transmission electron microscope (TEM) images reveals that the Cu SAs@MoS 2 is formed by the stacking of lamellar MoS 2 crystal structures (Supplementary Figs. S1b and S4). Two different lattice spacing of 0.73 and 0.62 nm are both observed, which can be indexed to the interlayer spacing of 1T and 2H MoS 2 , respectively (Supplementary Fig. S1 c) 30 . Moreover, a uniform Mosaic-like structure of MoS 2 is observed with mixed 1T and 2H phases in its HRTEM image (Supplementary Figs. S1d and e). Corresponding Energy-dispersive X-ray spectroscopy (EDS) and corresponding mapping measurement showed that Cu, Mo, and S were homogenously distributed (Supplementary Figs. S1f-i). The Cu content in Cu SAs@MoS 2 is estimated to be 0.64 wt% by Inductively coupled plasma-optical emission spectroscopy (ICP-OES, Supplementary Table S1 ). The X-ray diffraction (XRD) patterns (Supplementary Fig. S1 j) show the characteristic peaks of (002) plane of 1T phase MoS 2 and (002) plane of 2H phase MoS 2 at 2θ = 10° and 14°, respectively 31 . In the Raman spectra (Supplementary Fig. S1 k), the peaks at 147 cm − 1 and 195 cm − 1 correspond to the J 1 and J 2 interlayer vibrational modes of 1T MoS 2 32 , and the peak at 281 cm − 1 corresponds to the E 1g in-plane vibrational mode of 1T MoS 2 . The two distinct peaks at 334 and 374 cm − 1 correspond to the E 1 2g and A 1 g vibrational modes of 2H MoS 2 , respectively 33 . All these results clearly demonstrated that the crystalline MoS 2 matrix fabricated in this work possess a mixed crystal phase of 1T and 2H MoS 2 . Since the good electronic conductivity of 1T phase and the excellent visible light sensitivity of 2H phase 34 , this heterogeneous structure may provide enhanced PMEC performance due to the fast electron diffusion and effective light harvest. Figure 1 b presents the normalized Cu K-edge X-ray absorption near edge structure (XANES) spectra of Cu SAs@MoS 2 under dark condition for intrinsic characterization, using Cu foil, Cu 2 O and CuO as reference samples. The absorption edge of Cu SAs@MoS 2 is situated between that of Cu 2 O and CuO, indicating that the valence state of the Cu is between + 1 and + 2 35 . In its k 3 -weighted Fourier-transformed extended X-ray absorption fine structure (EXAFS) spectra collected under ex situ condition (Supplementary Fig. S5), a distinct and pronounced peak is recorded at 1.72 Å, which can be ascribed to the conventional Cu−S coordination, and no peaks corresponding to CuO or Cu 2 O were observed 35 . Moreover, the EXAFS fitting curves shows the structure of Cu SAs@MoS 2 with Cu−S 3 configuration (Fig. 1 c and Supplementary Figs. S6-9). Comparing to the normalized spectrum collected under dark condition, the normalized in situ XANES of Cu K-edge under light irradiation shows a clear negative shift to lower energy level, suggesting increased electron density and lower chemical valence state of Cu in this case (Fig. 1 d). 36 This result demonstrates the effective photo electron transfer pathway from MoS 2 to the Cu SAs, which favorable for the NORR on Cu SAs active sites. Furthermore, in situ EXAFS spectra fitted show that the position of the Cu peak also exhibits a shift of 0.06 Å under light illumination compared to that in the dark condition (Fig. 1 e and Supplementary Fig. S10). After fitting, it can be observed that the Cu−S extended from 2.27 Å to 2.34 Å with light illumination. Density functional theory (DFT) calculations of Cu SAs@MoS 2 at ground state and excited state was performed. As shown in Fig. 1 f, three Cu−S bonds lengths are 2.16, 2.16, 2.16 Å at ground state, theoretically. While under light irradiation, they extended to 2.61, 2.58, 2.61 Å at excited state, showing much longer bond length. This result agrees well with the observation from fitted in situ EXAFS spectra above. (Fig. 1 e, Supplementary Fig. S10 and Table S2). The low chemical valence and prolonged bond length indicates the modification of electron and physical properties on Cu SAs under light irradiation, which shows great potential in favoring NO discussed in following part and accelerating the NORR. Wavelet-transformed k 3 -weighted EXAFS (WT-EXAFS) analyses were conducted in both k and R spaces. The Cu SAs@MoS 2 displayed only one intensity maximum at approximately 1.50 Å −1 with and without light irradiation (Figs. 1 g and h). It further confirmed the identification of monodisperse Cu atoms, Cu−S coordination structures, and the activation state of Cu SAs under light. In addition, the Cu SAs@MoS 2 after illumination, the peak of Cu−S bond in the excited state changes toward the region of higher R-value, and the wavelet conversion of its phase information is sensitive to the change of bond length. The increase in bond length may lead to changes in the different scattering paths as well as an increase in disorder, which further induces the dispersion of the signal in R-space 37 , 38 . The increase in disorder is often accompanied by a lower intensity of the main peak in R-space, which has been shown in EAXFS (Figs. 1 g-k) 39 . It further confirmed the identification of monodisperse Cu atoms in Cu SAs@MoS 2 and the activation state of Cu SAs under light. X-ray photoelectron spectroscopy (XPS) was performed to elucidate the chemical configuration of the catalyst (Supplementary Fig. S11a). The Mo 3d 5/2 and Mo 3d 3/2 peaks at binding energies of 231.94 eV and 228.41 eV can be indexed to the 2H MoS 2 (Supplementary Fig. S11b), while the peaks at 230.65 eV and 227.39 eV were attributed to Mo 3d 5/2 and Mo 3d 3/2 of 1T MoS 2 40 . The XPS spectra at 2p signal of S shows similar results, which also clearly demonstrated the coexistence of 2H-MoS 2 and 1T-MoS 2 (Supplementary Fig. S11c). Accordingly, the contents of 1T and 2H phases can be estimated to be 57% and 43%, respectively 41 . From the 2p 2/3 spectra of Cu, Cu−S species (at 931.15 eV) can be observed (Supplementary Fig. S11d) 42 . PMEC-NORR performances in H-type cell The photocurrent response was evaluated. As displayed in Fig. 2 a, Cu SAs@MoS 2 showed 20 uA cm − 2 increased reduction current response with light on, indicating a photo-electron response at under this circumstance. The introduced light onto Cu SAs also leads to the emergence of localized energy levels on the surface of the material, 43 which affects the physical structure such as mentioned Cu−S bonds, the local electronic structure determine the catalytic Cu. A gentle peak to a sharp peak from substrate MoS 2 , the, illustrate the modified electron-transfer ability 44 . Figs. S12 a and b show the UV-Vis spectra and tauc plots of Cu SAs@MoS 2 and MoS 2 , respectively. It can be observed that Cu SAs on MoS 2 were almost exhibiting virtually unchanged bandgap width and light absorption. To verify the catalytic performances of Cu SAs@MoS 2 under synergistic photo and electric fields, NORR tests were performed in 0.5 M Na 2 SO 4 electrolyte using an air-tight H-type cell. Figure 2 b shows the linear sweep voltammetry (LSV) curves of Cu SAs@MoS 2 under various conditions. A significantly higher current density was achieved with NO saturated electrolyte than pure Ar saturated electrolyte under both dark and light conditions, implying the occurrence of NORR. Moreover, it also clearly shows that the visible light irradiation can obviously promote the catalytic reduction speed of NO. The Tafel slope of Cu SAs@MoS 2 under light conditions is estimated to be only 35.71 mV dec − 1 (Fig. 2 c), which is significantly lower than that measured under dark condition (54.03 mV dec − 1 ). These results demonstrate that the light irradiation effectively accelerated the NORR kinetics as expected. Besides, this Cu SAs@MoS 2 catalyst gives much faster reaction kinetics than pure MoS 2 (62.85 mV dec − 1 under light and 62.85 mV dec − 1 under dark, Supplementary Fig. S13). The colorimetric methods are used to quantify the liquid products (Supplementary Figs. S14 and S15), and the gas chromatography is adopted for gas products detection. The potential-dependent PMEC-NORR performances over Cu SAs@MoS 2 was investigated in Figs. 2 d and e. Considerable NH 3 yield and FE were achieved at -0.3 V vs RHE, which is significantly superior than that of EC-NORR without light. Only small amount of N 2 H 4 and N 2 were detected as byproducts (Supplementary Fig. S16), which is quite normal in NORR 45 . The alternating PMEC tests with and without NO (Supplementary Fig. S17), combination optimum-potential PMEC for 1 h in Ar-saturated electrolyte (Supplementary Fig. S18) and open-circuit voltage (OCP) in NO-saturated electrolyte (Supplementary Fig. S19) are sufficient to confirm that the PMEC-NORR products (NH 3 ) are all derived from the reduction of NO. The best NH 3 yield and FE were obtained at -0.3 V due to the synergistic catalytic effect under light and electro fields. Subsequent long-term test was also carried out at optimal − 0.3 V vs. RHE (Fig. 2 f). It demonstrated that Cu SAs@MoS 2 has excellent stability up to 10 h with no noticeable decline in its performance with this H-type cell (average yield of 62.76 µmol h − 1 mg − 1 and FE of 90%). As shown in Figs. 2 g and h, in case of Cu SAs@MoS 2 is used as catalyst, the NH 3 yield is 60.55 µmol h − 1 mg − 1 and FE is estimated to be 90.66% at -0.3 V vs RHE in the PMEC-NORR. As comparison, MoS 2 and Cu NWs samples were also tested under the same condition, delivering much lower NH 3 yields (17.11 and 25.63 µmol h − 1 mg − 1 ) and inferior FE (36.24% and 32.65%). This result demonstrated that Cu SAs loaded on MoS 2 provided enhanced catalytic activity of NORR compared to metal Cu NWs and pure MoS 2 samples. To further demonstrate the effectiveness of the light assistance in catalyzing the NORR, subsequent EC-NORR and PC-NORR tests were also performed. For EC-NORR, Cu SAs@MoS 2 exhibited an obvious decreased NH 3 yield of 35.61 µmol h − 1 mg − 1 and a lower FE of 80.26% without the light coupled. MoS 2 also displayed a similar decrease in NH 3 yield and FE in the absence of light irradiation. While Cu NWs showed similar performances in EC-NORR to its PMEC condition, because it is insensitive to light irradiation. A negligible NH 3 yield was detected under PC condition for all these samples, indicating that pure light irradiation cannot drive the NORR under this condition. Only with negative potential or current, process could be activated and further enhanced by introducing light-modulation. Clarification of the catalytic mechanisms To further investigate the role of Cu SAs and the effect of light irritation for the PMEC reaction, subsequent density functional theory (DFT) was performed. As shown in Fig. 3 a, the projected density of states of the Cu 3d orbitals at ground state is rarely available above the Fermi level in the energy range from 0 to 4 eV, whereas under light illumination a clear peak between 0 and 4 eV occurs, suggesting that a reduced state into the Cu 3d manifold. Figure 3 b complementary charge-density difference plots in the panels show that under light illumination, the integrated electron population in the Cu site increases from 0.14 e − in dark to 0.19 e − , suggesting that Cu SAs transitions into a localized electron trap. It is confirmed that this a electron accumulation at the Cu SAs site will enhance the activation of adsorbed NO by providing more electron for driving the whole NORR reaction from adsorbing NO and weakening N-O bond to the successive hydrogenation steps, thus facilitating the NORR process 46 – 49 . The theoretical optimized adsorption configurations of Cu SAs@MoS 2 and MoS 2 towards NO molecules and corresponding intermediates (Supplementary Figs. S20-23), as well as the corresponding Gibbs free energy (ΔG) are calculated using DFT. We proposed a possible reaction pathway for PMEC-NORR on Cu SAs@MoS 2 catalyst: *NO → *NHO → *NHOH → *NH 2 OH → *NH 2 → *NH 3 (Fig. 3 c). The hydrogenation of *NO to *NHO intermediates is considered as the RDS in this reaction. The ΔG for the production of *NHO intermediates on Cu SAs@MoS 2 catalyst is -1.3 eV, which is much more negative than that on MoS 2 catalyst, which is -0.15 eV (Fig. 3 d), which explains the significantly enhanced catalytic performance of the Cu SAs@MoS 2 material. To gain more insight of this PMEC-NORR, the operando photo-electrochemical attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) was utilized to monitor the absorbed intermediates produced during the reaction. In the time-dependent operando photo-electrochemical ATR-FTIR spectra, NO molecules are primarily adsorbed on the surface of Cu SAs@MoS 2 in a vertical vibrational mode with peaks at 1710 cm − 1 (Fig. 4 a) under light illumination 50 , 51 . The signal intensity is evidently higher than that recorded on MoS 2 material (Fig. 4 b), indicating that Cu SAs facilitates the alteration of the NO dipole moment, making it more favorable for activation into *NO. The hydrogenated intermediate *NHO appears at 1524 cm − 1 , suggesting that the first hydrogenation step occurs at the nitrogen end of NO molecule 50 . As the reaction goes on, the *NH 2 hydrogenated intermediate is observed at 1336 cm − 1 and 1506 cm − 1 , and a strong *NH x peak emerges at 1457 cm − 1 . The increasing intensity of these peaks along with reaction time indicates the accumulation of hydrogenated species on the surface of this catalyst. The potential-dependent operando photo-electrochemical ATR-FTIR spectra are also measured. Supplementary Fig. S24 shows that *NO, *NHO and *NH x intermediates on Cu SAs@MoS 2 become evident at a quite positive potential of + 0.1 V vs RHE, while MoS 2 requires a more negative potential of -0.1 V vs. RHE. This result indicates that Cu SAs@MoS 2 has lower overpotential than MoS 2 during the PMEC-NORR due to the active Cu SAs sites, which is in agreement with the PMEC performances. In Supplementary Fig. S25, we further explored the adsorption of *H on the surfaces of the catalysts by operando photo-electrochemical ATR-FTIR spectra depending on time and potential. It can be observed that Cu SAs@MoS 2 has strong *H adsorption peaks at 1965–1967 cm − 1 (Supplementary Figs. S25 a and b), which is more favorable for the hydrogenation of NO molecules to produce NH 3 product other than the combination of *H to produce H 2 52,53 . As comparison, MoS 2 shows much lower adsorption towards *H even at negative potential, which may lead to competitive H 2 evolution (Supplementary Figs. S25 c and d) 54 . As shown in Fig. 4 c, operando ATR-FTIR measurements under a constant current of 0.5 mA revealed that the characteristic bands at 1168 cm − 1 and 1140 cm − 1 , assignable to NO⁻ and *NOH intermediates, respectively, reproducibly exhibited higher intensities upon PMEC compared to the EC (repeated four times). This observation indicates that light irritation promotes hydrogenation at the O-terminus of NO, thereby facilitating the formation of *NOH species. To further probe the hydrogen radical dynamics, DMPO-trapped EPR experiments were performed. As shown in Figs. 4 d and e, Cu SAs@MoS 2 displayed a significantly stronger *H - related signal than MoS 2 , and the *H signal was further enhanced under light irradiation, evidencing the light-driven generation of reactive hydrogen species. Moreover, operando EPR under continuous NO flow (Figs. 4 f and g) revealed distinct time-dependent behaviors, for MoS 2 , the *H signal persisted even after 5 min, whereas for Cu SAs@MoS 2 , the *H species were completely consumed by this time. These results demonstrate that Cu SAs@MoS 2 not only increases the availability of *H but also accelerates its consumption in NO hydrogenation, thus providing direct evidence that light assists the electrocatalytic process by modulating both the hydrogenation pathway and *H dynamics. PMEC-NORR performances in flow cell Since the low solubility of diluted NO in aqueous electrolyte, gas-liquid-solid three-phase flow cell is considered as potential candidates for the practical NORR. It directly overcomes the NO's low solubility by enabling intense interaction between all reactant phases at the catalyst surface while ensuring stable, continuous operation. Thus, an PMEC-flow cell was designed in this work to evaluate the continuous NORR performances for the first time. As shown in Fig. 5 a, the cathode chamber is equipped with a quartz light window of 1×1 cm − 2 area for light illumination, and the NO gas and electrolyte flow into the chamber from the two separated inlets. Ag/AgCl and Pt electrodes were used as reference and counter electrode, respectively. Linear sweep voltammetry (LSV) curves of the PMEC-flow cell can be clearly observed that the introduction of photo field provides additional current density (Supplementary Fig. S26). The PMEC-flow cell performances were evaluated at different potentials as shown in Figs. 5 b, c and Supplementary Fig. S27a. The NH 3 yield of 254.8 µmol h − 1 mg − 1 at -0.4 V vs RHE with FE of 81.86% was achieved. The gas flow rate was optimized, showing best activity with 30 sccm due to the equilibrium adsorption on the surface of catalysts (Supplementary Figs. S28a and b). Subsequent constant-current PMEC-NORR was performed at gas flow rate of 30 sccm with current density in the range of 25–200 mA cm − 2 . An ultra-high NH 3 yield of 3228 µmol h − 1 mg − 1 as well as an excellent FE of 86.53% were achieved at a current density of 100 mA cm − 2 (Fig. 5 d and e, Supplementary Fig. S27b, Figs. S28c and d). Compared with the previously reported low concentration EC-NORR performances, this Cu SAs@MoS 2 with PMEC-NORR system showed highest NH 3 yield and FE (Fig. 5 f and Supplementary Table S3). Moreover, the long-term durability up to 45 h was achieved at current density of 100 mA cm − 2 , showing excellent stability, which is also promising for the industrial PMEC-NORR to produce NH 3 by flow cells (Fig. 5 g). Discussion Intuitively, obtaining high yield and high Faradaic efficiency simultaneously is difficult under low-concentration conditions. They are often considered as a trade-off relationship. However, by simply focusing on the design of the Cu coordination environment, this trade-off was seemly broken. We developed an advanced Cu single-atom catalyst to promote the electrochemical conversion of NO to NH 3 . The efficient NORR catalyst, Cu SAs@MoS 2 , was synthesized via a microwave-assisted method that enables the atomic dispersion of Cu sites on a mixed-phase MoS 2 substrate. Combined experimental characterizations and DFT calculations reveal that light irradiation modulates the local Cu–S coordination environment, thereby accelerating NORR kinetics through enhanced NO activation and a significantly reduced energy barrier for the rate-determining hydrogenation step. Benefiting from this photo-modulated electronic reconstruction, the PMEC flow cell achieves an ultra-high NH 3 yield of 3228 µmol h − 1 mg − 1 and FE of 86.53% at 100 mA cm − 2 . Such a high conversion rate in a low-concentration environment has not been reported before. This work demonstrates the strong potential of photo-modulated electrocatalysis for efficient NO valorization under practical conditions. The process mirrors the logic of natural photosynthesis—using light as a precise tool to activate and convert abundant but inert molecules (N 2 in nature) into valuable fertilizers. This photo-modulated electrocatalysis strategy presents a compelling pathway for the sustainable upcycling of low-concentration pollutants, including NO x , CO 2 and nitrates, moving us closer to smart, adaptive catalytic systems for closing anthropogenic chemical loops. Ultimately, this “artificial photo-electro nitrogen fixation” paradigm holds promise as a smart platform contributing to the realization of sustainable carbon- or nitrogen-negative chemical cycles and steering energy and environmental catalysis toward a new avenue of precision-controlled molecular transformation and circular economy. Methods Materials Carbon papers (HCP020N, thickness: 0.19 ± 0.01 mm) were purchased from Hesen company (Shanghai, China). Sodium hydroxide (NaOH AR) was purchased from Richjoint. hydrochloric acid (HCl) and sulphury acid (H 2 SO 4 ) were purchased from Sinopharm Chemical Reagent Co. Ltd., methanol (CH 3 OH), isopropanol (C 3 H 8 O), Cu(NO 3 ) 2 ·3H 2 O, N 2 H 4 , ethylenediamine (98%), thiourea (99%), ammonium chloride (NH 4 Cl), ethanol (C 2 H 5 OH), salicylic acid (C 7 H 6 O 3 ), trisodium citrate dihydrate (C 6 H 5 Na 3 O 7 ·2H 2 O, AR), p-dimethylaminobenzaldehyde (C 9 H 11 NO), sodium ferrocyanide nitrite dihydrate (C 5 FeN 6 NaO·2H 2 O), sodium hypochlorite (NaClO), ammonium molybdate ((NH) 6 Mo 2 O 24 ) (99%) were purchased from Aladdin Biochemical Technology Co., Ltd. Synthesis of Cu NWs Cu NWs were synthesized based on previous reports 55 . Specifically, 500 g of 85% aqueous NaOH solution was dissolved in 833 mL of deionized water under strong stirring, followed by the slow addition of 41.5 mL of a 0.1 M Cu(NO 3 ) 2 aqueous solution. After stirring for 40 minutes, 6.225 mL of ethylenediamine (H 2 NCH 2 CH 2 NH 2 ) solution and 1.037 mL of 35% N 2 H 4 aqueous solution were added. The mixture was transferred to a desiccator and heated at 80°C for 3 hours. Afterwards, the obtained copper nanowires were washed repeatedly with ethanol to remove the residual solvent and then sealed in ethanol. Synthesis of Cu SAs@MoS 2 Cu SAs@MoS 2 was prepared by modified microwave-assisted method 56 . Typically, 2 mmol of Cu NWs was dispersed in 20 mL of deionized water by sonication for 2 h, and then 0.5 mmol (NH) 6 Mo 2 O 24 (99%, Macklin) and 30 mmol thiourea (99%, Aladdin) were immediately added to the solution and dispersed well by sonication for 1 h. The well-mixed reactants were transferred to a quartz vessel equipped with a microwave system (Ethos TC, 1300 W). The reaction was heated for 20 min at 180 ℃ with a rising rate of 15°C min − 1 and an argon pressure of 35 bar. After cooling to room temperature, the product was thoroughly washed three times with deionized water and ethanol, respectively. Black powder was obtained after vacuum drying at 80°C for 12 h and denoted as Cu SAs@MoS 2 . Synthesis of MoS 2 Pure MoS 2 sample was synthesized by the similar method with Cu SAs@MoS 2 , except the addition of Cu NWs. XAFS and in situ XAFS experimental details The X-ray absorption data at the Cu K-edge of the samples were measured at room temperature in the fluorescent mode with the large solid angle Lytle detector at beamline BL14W1 of the Shanghai Synchrotron Radiation Facility (SSRF), China. The station was operated with a Si (111) double crystal monochromator. During the measurement, the storage ring was operated at the energy of 3.5 GeV and a current of 200 mA (top-up). In-situ XAFS test was carried out on the Cu SAs@MoS 2 under Xe lamp irradiation. The photon energy was calibrated with the first inflection point in Cu K-edge of Cu metal foil. The finely grounded sample powder was coated on the adhesive tape for XAFS measurements. Athena and Artemis codes were used to extract the data and fit the profiles. Physicochemical characterizations FESEM images were observed on field-emission scanning electron microscope (SEM, HITACHI, S-4800) and transmission electron microscopy (TEM) images were collected at an acceleration voltage of 200 kV (TEM, JEOL JEM-2100F). Powder Xray diffraction (XRD) was conducted on a Bruker D8 Advance X-ray powder diffractometer using Cu-Kα radiation (λ = 1.54 Å). The Co contents were estimated by Inductively Coupled Plasma-Optical Emission Spectrometry (ICP-OES, ICPE-9000, Shimadzu, Japan). XPS was measured by Thermo Scientific K-Alpha All the binding energy values were calibrated by using C1s = 284.6 eV as a reference. The UV-vis diffuse reflectance spectra (DRS) were obtained on a UV-vis spectrophotometer (UV-vis DRS, Shimadzu UV-2450). The Cu K-edge X-ray absorption fine structure spectroscopy (XAFS) was measured at the Shanghai Synchrotron Radiation Facility (SSRF), China. In situ attenuated total reflection Fourier transform infrared (ATR-FTIR) spectra were measured on a Thermo Scientific Nicolet 6700 spectrometer equipped with a PIKE VeeMAX III variable angle ATR sampling accessory.1H nuclear magnetic resonance (NMR) spectra were conducted on a Bruker Avance III HD 600 MHz spectrometer. Photo modulated-electrochemical measurements The photo switched electrocatalytic NO reduction reaction (PMEC-NORR) was carried out in a quartz H-type electrolytic reactor equipped with a light window. 40 mL 0.5 M Na 2 SO 4 solution was filled in each chamber as electrolyte. Nafion 117 membrane was first boiled in boiling water for 1 h, followed by treatment with H 2 O 2 (5 wt%) at 80°C for 1 h. Subsequent protonation of the membranes was carried out using 0.5 M H 2 SO 4 at 80°C for 3 h to maintain the temperature after protonation in water for a final treatment of 6 h. Then, it was used to separate cathode and anode chambers. In order to avoid unwanted formation of nitrogen dioxide (NO 2 ) due to easy oxidation of NO by O 2 , high-purity Ar (99.99%) was passed through the electrolyze for 30 min to remove residual oxygen. All photoelectrochemical tests were performed using a CHI 760E photoelectrochemical test using a three-electrode system. Pt sheet and Ag/AgCl (saturated KCl electrolyte) were used of counter and reference electrodes, respectively. A carbon paper (1×1 cm − 2 ) loaded with 1 mg catalyst was used as working electrode in the H-type cell. In the flow cell, the loading was decreased to 0.20 mg cm − 1 . Xenon lamp (150 W) equipped with a UV cut filter to cut off lights (λ < 420 nm) was used as light source. All potentials were referenced against the reversible hydrogen electrode (RHE) based on the Nernst equation (E RHE = E Ag/AgCl + 0.059 × pH + 0.197). The linear sweep voltammetry (LSV) tests were all performed at a scanning speed of 5 mV s − 1 . For evaluation of performances of PMEC-NORR over these catalysts, the chronoamperometry (CA) tests were conducted in NO-saturated 0.5 M Na 2 SO 4 electrolyte using a NO/Ar gas mixture (10% NO, 30 sccm) continuously vented to the cathode of the electrolytic cell, with continuous stirring (at 500 rpm). 4 M KOH and acidic KMnO 4 solutions were used for NO tail gas absorption. The gas flow rate was controlled by the mass flow controllers (Beijing I Know Meter Science and Technology Ltd.). Products detection Determination of NH 3 The amount of NH 3 was determined by colorimetry using the indophenol blue method. A certain amount of electrolyte was taken out from the electrolytic cell and diluted to 2 mL to the detection range. Then, 2 mL of a 1 M NaOH solution that contained salicylic acid and sodium citrate was added. Then, 1 mL of 0.05 M NaClO and 0.2 mL of 1 wt% C 5 FeN 6 Na 2 O·2H 2 O were added to the above solution. After standing for 2 h at room temperature, the UV-Vis absorption spectrum was measured. The concentration of NH 3 was determined using the absorbance at a wavelength of 660 nm. The concentration-absorbance curve was calibrated using a series of standard NH 4 Cl solutions. The fitting curve (y = 0.119x + 0.0014, R 2 = 0.999) showed good linear relation of absorbance value with NH 3 concentrations. Determination of N 2 H 4 The N 2 H 4 presented in the electrolyte was estimated by Watt and Chrisp method. Color reagent includes C 9 H 11 NO (5.99 g), HCl (concentrated, 30 mL) and ethanol (300 mL). 1 mL above color reagent and 1 mL electrolyte were mixed and stirred 15 min at room temperature. The concentration of N 2 H 4 was determined using the absorbance at a wavelength of 455 nm. The absorbance curves were calibrated using standard N 2 H 4 solution with a series of concentrations. Determination of NO 3 − Firstly, a certain amount of electrolyte was taken out from the electrolytic cell and diluted to 5 mL to the detection range. Then, 0.1 mL 1 M HCl and 0.01 mL 0.8 wt% sulfamic acid solution were added into the aforementioned solution. The absorption spectrum was measured using a UV-Vis spectrophotometer and the absorption intensities at a wavelength of 220 nm and 275 nm were recorded. The final absorbance value was calculated by this equation: A = A 220 nm – 2A 275 nm. The concentration-absorbance curve was calibrated using a series of standard NaNO 3 solutions and the NaNO 3 crystal was dried at 110 ºC for 2 h in advance. Determination of H 2 and N 2 H 2 and N 2 was monitored by gas chromatography (GC). Determining FE and NH 3 yield The FE for NH 3 photoelectrosynthesis is defined as the ratio of the charge utilized for NH 3 production to the total charge passing through the electrode during electrolysis. This can be expressed mathematically using the following formula: FE = n × F × c × V / (M × Q) (1) The NH 3 yield was calculated using the following equation: NH 3 yield = c × V / (17 × t × S) (2) Where n is the number of electrons was needed to produce one product molecule; F is Faraday constant (96485 C mol − 1 ); c is the measured mass concentration of product; V is the volume of the cathodic reaction electrolyte (40 mL); M is relative molecular mass of specific product; Q is the quantity of applied charge/electricity; t is the time for which the potential was applied (1 h); S is the geometric area of the working electrode (1 cm 2 ). In situ ATR-FTIR test The crystalline silicon substrates were covered with a gold film to increase the reflected signals. The catalyst-loaded gold film supported by crystalline silicon, Pt, and Ag/AgCl electrodes served as the working electrode, counter electrode, and reference electrode, respectively. The H-shaped electrolytic cell was made of quartz. The light sources were Xenon lamp (150 W) equipped with a UV cut filter to cut off lights (λ < 420 nm) was used as light source. Computational details The spin-polarized density functional theory (DFT) calculations have been conducted on Vienna ab-initio simulation package (VASP) 57 , 58 to study the catalytic process of prepared catalysts. The generalized gradient approximation proposed by Perdew-Burke-Ernzerhof (PBE) is selected for the exchange-correlation potential 59 , 60 . The cut-off energy for plane wave is set to 500 eV. The energy criterion is set to 10 − 5 eV in the iterative solution of the Kohn-Sham equation. To avoid interlaminar interactions, a vacuum spacing of 20 Å is applied perpendicular to the slab. The Brillouin zone integration is performed using a 3×3×1 k-mesh. All the structures are relaxed until the residual forces on the atoms have declined to less than 0.02 eV/Å. DFT-D3 method 61 was used to correct the influence of van der Waals interactions. Two layers of 1T-MoS 2 (001) facets have been cleaved with a vacuum of 15 Å to build the slab models. The adsorption energy (E ads ) has been calculated using formula 3: $$\:{E}_{ads}={E}_{total}-{E}_{substrate}-{E}_{adsorbate}\:\:\:\:\left(3\right)$$ The E total , E substrate and E adsorbate represent the energy of adsorption structure, substrate and adsorbate, respectively. The free energies have been calculated using the following formula 4: $$\:G=\:{E}_{DFT}+ZPE-TS\:\:\:\:\left(4\right)$$ The G, E DFT , ZPE and TS represent the free energy, energy from DFT calculations, zero-point energy and entropic contributions, respectively. Declarations Competing interests The authors declare no competing interests. Author contributions X.L. and Z.L. conceived the project, carried out the experiments, analyze the data and wrote the draft of manuscript. S.H. and W.T. carried out the EXAF experiments, theoretical calculation, data analysis and manuscript revision. L. H., L.H., Q.W., S.L., X.W., and T.L. contributed to the experimental synthesis, catalysts characterization and electrochemical measurements. G.L. and H.L. discussed and revised the manuscript. D.Z. and J. L. supervised the project, manuscript preparation and discussion. Acknowledgments This work was supported by the National Natural Science Foundation of China (22376142, 22305157, 22236005, 22022608, 22176127), National Key Research and Development Program of China (2020YFA0211004), the Shanghai Engineering Research Center of Green Energy Chemical Engineering (18DZ2254200), and “111” Innovation and Talent Recruitment Base on Photochemical and Energy Materials (D18020), the Shanghai Government (22010503400, 23520711100, 218014346, 18SG41, YDZX20213100003002) Shanghai Scientific and Technological Innovation Project (21DZ1206300). 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07:48:08","extension":"png","order_by":10,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":295708,"visible":true,"origin":"","legend":"","description":"","filename":"Onlinefloatimage2.png","url":"https://assets-eu.researchsquare.com/files/rs-8346707/v1/5bc4bc6756cd05f2aeafebbd.png"},{"id":99308855,"identity":"66f349ad-918a-4630-bda2-983273379b01","added_by":"auto","created_at":"2025-12-31 16:09:21","extension":"png","order_by":11,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":354419,"visible":true,"origin":"","legend":"","description":"","filename":"Onlinefloatimage3.png","url":"https://assets-eu.researchsquare.com/files/rs-8346707/v1/8140c52623ca2435e67628c8.png"},{"id":99308581,"identity":"cf99d3ad-04dc-4954-8437-b1e3685086ec","added_by":"auto","created_at":"2025-12-31 16:08:48","extension":"png","order_by":12,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":1436629,"visible":true,"origin":"","legend":"","description":"","filename":"Onlinefloatimage4.png","url":"https://assets-eu.researchsquare.com/files/rs-8346707/v1/a80938c29f75b94407e2102b.png"},{"id":99308365,"identity":"8888ee73-3034-4792-8ab4-27ac8e99fa5e","added_by":"auto","created_at":"2025-12-31 16:08:21","extension":"png","order_by":13,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":477462,"visible":true,"origin":"","legend":"","description":"","filename":"Onlinefloatimage5.png","url":"https://assets-eu.researchsquare.com/files/rs-8346707/v1/e90b573064a45391a3fd804d.png"},{"id":98855872,"identity":"d74148c5-6a7b-43fa-bb9e-9fb49532d377","added_by":"auto","created_at":"2025-12-23 07:48:08","extension":"xml","order_by":14,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":133156,"visible":true,"origin":"","legend":"","description":"","filename":"NCOMMS250989400structuring.xml","url":"https://assets-eu.researchsquare.com/files/rs-8346707/v1/b70cd23eaf2bc2a90458c961.xml"},{"id":98855880,"identity":"ad29f7a1-a21f-4d8a-b3ca-4d2b0fa259e3","added_by":"auto","created_at":"2025-12-23 07:48:08","extension":"html","order_by":15,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":142562,"visible":true,"origin":"","legend":"","description":"","filename":"earlyproof.html","url":"https://assets-eu.researchsquare.com/files/rs-8346707/v1/bbeb12b21605c96dfc48e652.html"},{"id":98855862,"identity":"8e026f82-a2a5-4fc6-9915-176a3a401c49","added_by":"auto","created_at":"2025-12-23 07:48:08","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":486015,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eSynthetic processes and characterizations of\u003c/strong\u003e \u003cstrong\u003eCu SAs@MoS\u003c/strong\u003e\u003csub\u003e\u003cstrong\u003e2\u003c/strong\u003e\u003c/sub\u003e\u003cstrong\u003e. a\u003c/strong\u003e Schematic illustration of synthetic processes for Cu SAs@MoS\u003csub\u003e2\u003c/sub\u003e. \u003cstrong\u003eb\u003c/strong\u003e Normalized Cu K-edge XANES spectra of Cu SAs@MoS\u003csub\u003e2\u003c/sub\u003e, Cu foil, Cu\u003csub\u003e2\u003c/sub\u003eO, and CuO samples under dark condition. \u003cstrong\u003ec\u003c/strong\u003e Corresponding EXAFS fitting curves and schematic configuration for Cu SAs@MoS\u003csub\u003e2\u003c/sub\u003e under dark condition (yellow sphere for S, purple sphere for Mo, orange sphere for Cu). \u003cstrong\u003ed\u003c/strong\u003e Normalized Cu K-edge\u003cem\u003e in situ \u003c/em\u003eXANES spectra for Cu SAs@MoS\u003csub\u003e2\u003c/sub\u003e.\u003cstrong\u003e e \u003c/strong\u003e\u003cem\u003eIn situ\u003c/em\u003e EXAFS spectra fitted of Cu SAs@MoS\u003csub\u003e2\u003c/sub\u003e under dark and light.\u003cstrong\u003e f \u003c/strong\u003eOptimized structural configurations of Cu SAs@MoS\u003csub\u003e2\u003c/sub\u003e at ground state and excited state.\u003cstrong\u003e g-k \u003c/strong\u003eWavelet transform k\u003csub\u003e3\u003c/sub\u003e-weighted EXAFS of Cu SAs@MoS\u003csub\u003e2 \u003c/sub\u003e(under dark or light), Cu foil, Cu\u003csub\u003e2\u003c/sub\u003eO, and CuO samples.\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-8346707/v1/96b6f2a801e4c5b9ac756b7c.png"},{"id":98855863,"identity":"fd8730f5-b98f-4e25-b2c6-6ab05ffd6d55","added_by":"auto","created_at":"2025-12-23 07:48:08","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":233031,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003ePMEC performances of catalysts in in H-type cell configuration. a\u003c/strong\u003e Transient photocurrent response of Cu SAs@MoS\u003csub\u003e2\u003c/sub\u003e under dark and light conditions. \u003cstrong\u003eb\u003c/strong\u003e LSV curves and \u003cstrong\u003ec\u003c/strong\u003e Tafel slopes of Cu SAs@MoS\u003csub\u003e2\u003c/sub\u003e in pure Ar or 10 vol% NO/Ar mixture atmosphere under light and dark conditions, respectively.\u003cstrong\u003e d\u003c/strong\u003e Yield and \u003cstrong\u003ee\u003c/strong\u003e FE of NH\u003csub\u003e3\u003c/sub\u003e product over Cu SAs@MoS\u003csub\u003e2\u003c/sub\u003e under PMEC-NORR at various potentials.\u003cstrong\u003e f\u003c/strong\u003e PMEC-NORR stability test over Cu SAs@MoS\u003csub\u003e2\u003c/sub\u003e at -0.3 V vs. RHE. \u003cstrong\u003eg \u003c/strong\u003eNH\u003csub\u003e3\u003c/sub\u003e yield and FE measured over Cu SAs@MoS\u003csub\u003e2\u003c/sub\u003e, MoS\u003csub\u003e2\u003c/sub\u003e, and Cu NWs catalysts under PMEC, EC and PC conditions (at -0.3 V vs. RHE for PMEC and EC). (0.5 M Na\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e solution was used as electrolyte. All the light irradiation was carried out by Xe lamp with λ \u0026gt; 420 nm).\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-8346707/v1/724fc2a64d71eacf23ca7b6f.png"},{"id":98855864,"identity":"34af0e7c-992d-40d7-83a3-8192f1d57cf4","added_by":"auto","created_at":"2025-12-23 07:48:08","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":322269,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eTheoretical calculations of PMEC-NORR.\u003c/strong\u003e \u003cstrong\u003ea \u003c/strong\u003ePartial density of state (PDOS) for Cu \u003cem\u003ed\u003c/em\u003e-orbitals at ground state and excited state, respectively. \u003cstrong\u003eb \u003c/strong\u003eElectron density difference for NO* adsorbed on Cu SAs@MoS\u003csub\u003e2\u003c/sub\u003e at ground state and excited state, respectively. Cyan and yellow represent electron accumulation and electron depletion, respectively.\u003cstrong\u003e c\u003c/strong\u003e Schematic illustration of the PMEC-NORR processes on Cu SAs@MoS\u003csub\u003e2 \u003c/sub\u003e(the different colored spheres represent atoms of different elements, yellow for S, purple for Mo, orange for Cu, blue for N, red for O, and pink for H). \u003cstrong\u003ed\u003c/strong\u003e Free energy diagram of PMEC-NORR processes over Cu SAs@MoS\u003csub\u003e2\u003c/sub\u003e and MoS\u003csub\u003e2\u003c/sub\u003e, respectively.\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-8346707/v1/1ca1e644f75b5c3d32b3ae9a.png"},{"id":98855869,"identity":"a4745fbe-317b-4856-9381-117e0495006b","added_by":"auto","created_at":"2025-12-23 07:48:08","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":395026,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eMechanism investigations of PMEC-NORR. \u003c/strong\u003eTime-dependent operando ATR-FTIR spectra of PMEC-NORR over \u003cstrong\u003ea\u003c/strong\u003e Cu SAs@MoS\u003csub\u003e2\u003c/sub\u003e and \u003cstrong\u003eb\u003c/strong\u003e MoS\u003csub\u003e2\u003c/sub\u003e. \u003cstrong\u003ec \u003c/strong\u003eOperando ATR-FTIR with and without light irritation under constant current (0.5 mA), repeated four times. DMPO-involved EPR spectra \u003cstrong\u003ed\u003c/strong\u003e of Cu SAs@MoS\u003csub\u003e2\u003c/sub\u003e and \u003cstrong\u003ee\u003c/strong\u003e MoS\u003csub\u003e2\u003c/sub\u003e (with and without light irritation). DMPO-involved EPR spectra of \u003cstrong\u003ef\u003c/strong\u003e Cu SAs@MoS\u003csub\u003e2\u003c/sub\u003e and \u003cstrong\u003eg\u003c/strong\u003e MoS\u003csub\u003e2\u003c/sub\u003e under continuous NO gas flow.\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-8346707/v1/d955baae63f1ddaaed835898.png"},{"id":98855877,"identity":"031044f3-a95e-495f-9960-1ebfc088c7f3","added_by":"auto","created_at":"2025-12-23 07:48:08","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":225223,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003ePMEC-NORR performances in flow cell configuration. a\u003c/strong\u003e Schematic illustration of PMEC-flow cell for NORR. \u003cstrong\u003eb\u003c/strong\u003e Products yield and \u003cstrong\u003ec \u003c/strong\u003ecorresponding FE at various potentials over Cu SAs@MoS\u003csub\u003e2\u003c/sub\u003e catalyst in PMEC-flow cells. \u003cstrong\u003ed\u003c/strong\u003e NH\u003csub\u003e3\u003c/sub\u003e yield, \u003cstrong\u003ee\u003c/strong\u003e corresponding FE at various current density. \u003cstrong\u003ef\u003c/strong\u003e Comparison of PMEC-NORR performances over Cu SAs@MoS\u003csub\u003e2\u003c/sub\u003e and previously reported EC-NORR works. \u003cstrong\u003eg\u003c/strong\u003e PMEC-flow cell voltage at current density of 100 mA cm\u003csup\u003e-2\u003c/sup\u003e over 45 h. (The other reaction conditions are as given in Fig. 2.)\u003c/p\u003e","description":"","filename":"5.png","url":"https://assets-eu.researchsquare.com/files/rs-8346707/v1/6e15ed26f7c60585fbac0353.png"},{"id":104401783,"identity":"135edca6-3d1a-439f-b36e-bfee8a221c2d","added_by":"auto","created_at":"2026-03-11 12:13:33","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":2455339,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-8346707/v1/833879b3-9757-47dc-9d30-22d0227bc965.pdf"},{"id":99308391,"identity":"9c305e75-d7ce-45f1-a840-fea8675d470c","added_by":"auto","created_at":"2025-12-31 16:08:24","extension":"docx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":3104025,"visible":true,"origin":"","legend":"Efficient Ammonia Production from Nitric Oxide under Real Condition Using Photo-Modulated Cu Single-Atom Catalysts","description":"","filename":"SupportingInformationEfficientAmmoniaProductionfromNitricOxideunderRealConditionUsingPhotoModulatedCuSingleAtomCatalysts.docx","url":"https://assets-eu.researchsquare.com/files/rs-8346707/v1/c07de4f9611816c00a8e799b.docx"}],"financialInterests":"There is \u003cb\u003eNO\u003c/b\u003e Competing Interest.","formattedTitle":"Efficient Ammonia Production from Nitric Oxide under Real Condition Using Photo-Modulated Cu Single-Atom Catalysts","fulltext":[{"header":"Introduction","content":"\u003cp\u003eExcessive anthropogenic emissions of nitric oxide (NO) as a major pollutant urgently demand an economical removal strategy\u003csup\u003e\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e,\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e\u003c/sup\u003e due to its environmental hazards (e.g., photochemical smog, ozone layer depletion, and acid rain).\u003csup\u003e\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e,\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e\u003c/sup\u003e Traditional selective catalytic reduction (SCR) technology for NO removal operating at high temperature with external reductant (NH\u003csub\u003e3\u003c/sub\u003e) and thus requiring invest substantial capital investment and utilization of pressure-equipment, which is not cost-efficient\u003csup\u003e\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e,\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e\u003c/sup\u003e. Thus, renewable clean-energy-driven electro catalysis (EC) of NO reduction (NORR) to ammonia (NH\u003csub\u003e3\u003c/sub\u003e) has attracted great interest as one of alternative approaches. This process utilizes electric derived from clean energy and the reaction occurs in aqueous solution, making it safe and environmentally friendly\u003csup\u003e\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eNotably, the actual NO concentration in exhaust gases is quite low, and its solubility in aqueous solution is also limited\u003csup\u003e\u003cspan additionalcitationids=\"CR9\" citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e\u003c/sup\u003e. This makes direct electro-reduction and meantime achieving high-yield performance in continues flow cell a great challenge\u003csup\u003e\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e,\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e\u003c/sup\u003e. Moreover, the NORR process involves multiple proton-coupled electron transfer process, suffering from complex intermediates and byproducts, which often leads to low yield and uncontrollable selectivity\u003csup\u003e\u003cspan additionalcitationids=\"CR14\" citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e\u003c/sup\u003e. Critical challenge lies in efficiently adsorbing and activating NO molecules at low concentrations, where enhanced NO affinity and effective suppression of the competing hydrogen evolution reaction (HER) are required. At higher current densities, overpotential-induced losses and mass-transport limitations further reduce the Faradaic efficiency (FE), complicating practical applications\u003csup\u003e\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eEfforts at early years have been devoted for selecting electrocatalysts at concentrated NO\u003csup\u003e17\u003c/sup\u003e. Among them, inexpensive Cu is proved to be one of the effective candidates owing to its apex location on NORR catalytic volcano plot by theoretical calculation\u003csup\u003e\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e,\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e\u003c/sup\u003e. A high NH\u003csub\u003e3\u003c/sub\u003e yield and FE were achieved by Cu foam at high NO concentration of 99.5% with overpotential up to -0.9 V (versus reversible hydrogen electrode, vs. RHE). With excellent intrinsic catalytic behavior of Cu, including crystal engineering (Cu(111) nanosheets)\u003csup\u003e\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e\u003c/sup\u003e, metal alloying (CuNi@BCN)\u003csup\u003e\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e\u003c/sup\u003e, construction of nanocomposites (S-Cu@Co/C)\u003csup\u003e22\u003c/sup\u003e and Cu single atoms (Cu SAs)\u003csup\u003e\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e\u003c/sup\u003e, various studies have been conducted for pursuing high NH\u003csub\u003e3\u003c/sub\u003e yield and FE\u003csup\u003e18\u003c/sup\u003e. However, when the concentration moved to real condition, the FE of Cu are dropping to below 10%\u003csup\u003e24\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eIntuitively, lowering the NO concentration reduces the frequency of reactant-catalyst encounters. Strategies such as carbon-supported Cu nanoparticles and Co-Ru dual-site catalysts have been proposed to accelerate three-phase mass transport and reaction kinetics, thereby partially mitigating this limitation\u003csup\u003e\u003cspan additionalcitationids=\"CR26\" citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e\u003c/sup\u003e. While these approaches enhance accessibility to active sites, they primarily address structural or transport-related bottlenecks. Besides structure evolution by exposing more active sites, focusing on modification on the intrinsic electronic characteristics of Cu, determine the adsorption energy and kinetics and directly affect FE and current density\u003csup\u003e\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e,\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e\u003c/sup\u003e. Nevertheless, these geometric modifications fail to rectify the intrinsic inertness of the catalytic center towards trace-level reactants. Merely increasing the number of sites is insufficient; the fundamental electronic propensity of the active site to capture and activate low-abundance NO must be radically enhanced.\u003c/p\u003e \u003cp\u003eIn this work, we focus on dynamic orbital engineering via a photo-modulated electrocatalysis (PMEC) system to surmount these intrinsic limitations in trade-offs of NORR. The catalyst, consisting of atomically dispersed Cu single atoms anchored on MoS\u003csub\u003e2\u003c/sub\u003e nanosheets (Cu SAs@MoS\u003csub\u003e2\u003c/sub\u003e), demonstrates markedly enhanced NORR activity. Under illumination, light acts as a remote \u0026ldquo;switch\u0026rdquo; to manipulate the local coordination environment, and the redesigned Cu\u0026minus;S bonds undergo electronic and geometric perturbations that strengthen NO adsorption and substantially facilitate the protonation of the *NO intermediate, thereby accelerating the overall reaction kinetics. When orchestrated in a continuous-flow reactor, the Cu SAs@MoS₂ catalyst delivers an NH\u003csub\u003e3\u003c/sub\u003e production rate of 3228 \u0026micro;mol cm\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e h\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e and FE of 86.53% at 100 mA cm\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e under 10 vol% NO, representing the highest performance reported for NORR and setting a new benchmark for NORR under dilute conditions. This work demonstrates dynamic modulation on Cu\u0026minus;S bonds and interactions between reactants can be harnessed to overcome fundamental limitations of low-concentration small-molecule adsorption, suggesting that dynamic modulation of the coordination sphere is a potent avenue for catalyzing low-concentration reactions.\u003c/p\u003e"},{"header":"Results","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003eSynthesis and characterizations\u003c/h2\u003e \u003cp\u003eAs illustrated in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ea, Cu SAs@MoS\u003csub\u003e2\u003c/sub\u003e material was synthesized by a microwave-assisted hydrothermal method using uniformly dispersed copper nanowires (Cu NWs), Mo\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e24\u003c/sub\u003e\u003csup\u003e6\u0026minus;\u003c/sup\u003e, and thiourea as copper, molybdenum and sulfide sources, respectively. In the initial stage, MoS\u003csub\u003e2\u003c/sub\u003e grew on the surface of Cu NWs, forming a one dimensional wormlike morphology. During the continuous microwave heating process, copper nanowires gradually dissolve and re-precipitate on the preformed MoS\u003csub\u003e2\u003c/sub\u003e substrate at single atom states in the later stage. The scanning electron microscope (SEM) image clearly demonstrates that the wormlike Cu SAs@MoS\u003csub\u003e2\u003c/sub\u003e is assembled by MoS\u003csub\u003e2\u003c/sub\u003e nanosheets (Supplementary Fig. \u003cspan refid=\"MOESM1\" class=\"InternalRef\"\u003eS1\u003c/span\u003ea). Without the addition of Cu NWs, pure MoS\u003csub\u003e2\u003c/sub\u003e with a spherical morphology was also synthesized by the same hydrothermal synthesis method as a reference sample (Supplementary Figs. S2 and S3). The difference in morphology between these two materials indicate that the copper nanowires served as morphology regulating template in the early stage.\u003c/p\u003e \u003cp\u003eThe transmission electron microscope (TEM) images reveals that the Cu SAs@MoS\u003csub\u003e2\u003c/sub\u003e is formed by the stacking of lamellar MoS\u003csub\u003e2\u003c/sub\u003e crystal structures (Supplementary Figs. S1b and S4). Two different lattice spacing of 0.73 and 0.62 nm are both observed, which can be indexed to the interlayer spacing of 1T and 2H MoS\u003csub\u003e2\u003c/sub\u003e, respectively (Supplementary Fig. \u003cspan refid=\"MOESM1\" class=\"InternalRef\"\u003eS1\u003c/span\u003ec)\u003csup\u003e\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e\u003c/sup\u003e. Moreover, a uniform Mosaic-like structure of MoS\u003csub\u003e2\u003c/sub\u003e is observed with mixed 1T and 2H phases in its HRTEM image (Supplementary Figs. S1d and e). Corresponding Energy-dispersive X-ray spectroscopy (EDS) and corresponding mapping measurement showed that Cu, Mo, and S were homogenously distributed (Supplementary Figs. S1f-i). The Cu content in Cu SAs@MoS\u003csub\u003e2\u003c/sub\u003e is estimated to be 0.64 wt% by Inductively coupled plasma-optical emission spectroscopy (ICP-OES, Supplementary Table \u003cspan refid=\"MOESM1\" class=\"InternalRef\"\u003eS1\u003c/span\u003e). The X-ray diffraction (XRD) patterns (Supplementary Fig. \u003cspan refid=\"MOESM1\" class=\"InternalRef\"\u003eS1\u003c/span\u003ej) show the characteristic peaks of (002) plane of 1T phase MoS\u003csub\u003e2\u003c/sub\u003e and (002) plane of 2H phase MoS\u003csub\u003e2\u003c/sub\u003e at 2θ\u0026thinsp;=\u0026thinsp;10\u0026deg; and 14\u0026deg;, respectively\u003csup\u003e\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e\u003c/sup\u003e. In the Raman spectra (Supplementary Fig. \u003cspan refid=\"MOESM1\" class=\"InternalRef\"\u003eS1\u003c/span\u003ek), the peaks at 147 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e and 195 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e correspond to the J\u003csub\u003e1\u003c/sub\u003e and J\u003csub\u003e2\u003c/sub\u003e interlayer vibrational modes of 1T MoS\u003csub\u003e2\u003c/sub\u003e\u003csup\u003e32\u003c/sup\u003e, and the peak at 281 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e corresponds to the E\u003csub\u003e1g\u003c/sub\u003e in-plane vibrational mode of 1T MoS\u003csub\u003e2\u003c/sub\u003e. The two distinct peaks at 334 and 374 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e correspond to the E\u003csup\u003e1\u003c/sup\u003e\u003csub\u003e2g\u003c/sub\u003e and A\u003csup\u003e1\u003c/sup\u003e\u003csub\u003eg\u003c/sub\u003e vibrational modes of 2H MoS\u003csub\u003e2\u003c/sub\u003e, respectively\u003csup\u003e\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e\u003c/sup\u003e. All these results clearly demonstrated that the crystalline MoS\u003csub\u003e2\u003c/sub\u003e matrix fabricated in this work possess a mixed crystal phase of 1T and 2H MoS\u003csub\u003e2\u003c/sub\u003e. Since the good electronic conductivity of 1T phase and the excellent visible light sensitivity of 2H phase\u003csup\u003e\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e\u003c/sup\u003e, this heterogeneous structure may provide enhanced PMEC performance due to the fast electron diffusion and effective light harvest.\u003c/p\u003e \u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eb presents the normalized Cu K-edge X-ray absorption near edge structure (XANES) spectra of Cu SAs@MoS\u003csub\u003e2\u003c/sub\u003e under dark condition for intrinsic characterization, using Cu foil, Cu\u003csub\u003e2\u003c/sub\u003eO and CuO as reference samples. The absorption edge of Cu SAs@MoS\u003csub\u003e2\u003c/sub\u003e is situated between that of Cu\u003csub\u003e2\u003c/sub\u003eO and CuO, indicating that the valence state of the Cu is between +\u0026thinsp;1 and +\u0026thinsp;2\u003csup\u003e35\u003c/sup\u003e. In its k\u003csub\u003e3\u003c/sub\u003e-weighted Fourier-transformed extended X-ray absorption fine structure (EXAFS) spectra collected under \u003cem\u003eex situ\u003c/em\u003e condition (Supplementary Fig. S5), a distinct and pronounced peak is recorded at 1.72 \u0026Aring;, which can be ascribed to the conventional Cu\u0026minus;S coordination, and no peaks corresponding to CuO or Cu\u003csub\u003e2\u003c/sub\u003eO were observed\u003csup\u003e\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e\u003c/sup\u003e. Moreover, the EXAFS fitting curves shows the structure of Cu SAs@MoS\u003csub\u003e2\u003c/sub\u003e with Cu\u0026minus;S\u003csub\u003e3\u003c/sub\u003e configuration (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ec and Supplementary Figs. S6-9). Comparing to the normalized spectrum collected under dark condition, the normalized \u003cem\u003ein situ\u003c/em\u003e XANES of Cu K-edge under light irradiation shows a clear negative shift to lower energy level, suggesting increased electron density and lower chemical valence state of Cu in this case (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ed). \u003csup\u003e36\u003c/sup\u003e This result demonstrates the effective photo electron transfer pathway from MoS\u003csub\u003e2\u003c/sub\u003e to the Cu SAs, which favorable for the NORR on Cu SAs active sites. Furthermore, \u003cem\u003ein situ\u003c/em\u003e EXAFS spectra fitted show that the position of the Cu peak also exhibits a shift of 0.06 \u0026Aring; under light illumination compared to that in the dark condition (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ee and Supplementary Fig. S10). After fitting, it can be observed that the Cu\u0026minus;S extended from 2.27 \u0026Aring; to 2.34 \u0026Aring; with light illumination. Density functional theory (DFT) calculations of Cu SAs@MoS\u003csub\u003e2\u003c/sub\u003e at ground state and excited state was performed. As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ef, three Cu\u0026minus;S bonds lengths are 2.16, 2.16, 2.16 \u0026Aring; at ground state, theoretically. While under light irradiation, they extended to 2.61, 2.58, 2.61 \u0026Aring; at excited state, showing much longer bond length. This result agrees well with the observation from fitted \u003cem\u003ein situ\u003c/em\u003e EXAFS spectra above. (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ee, Supplementary Fig. S10 and Table S2). The low chemical valence and prolonged bond length indicates the modification of electron and physical properties on Cu SAs under light irradiation, which shows great potential in favoring NO discussed in following part and accelerating the NORR. Wavelet-transformed k\u003csub\u003e3\u003c/sub\u003e-weighted EXAFS (WT-EXAFS) analyses were conducted in both \u003cem\u003ek\u003c/em\u003e and \u003cem\u003eR\u003c/em\u003e spaces. The Cu SAs@MoS\u003csub\u003e2\u003c/sub\u003e displayed only one intensity maximum at approximately 1.50 \u0026Aring;\u003csup\u003e\u0026minus;1\u003c/sup\u003e with and without light irradiation (Figs.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eg and h). It further confirmed the identification of monodisperse Cu atoms, Cu\u0026minus;S coordination structures, and the activation state of Cu SAs under light. In addition, the Cu SAs@MoS\u003csub\u003e2\u003c/sub\u003e after illumination, the peak of Cu\u0026minus;S bond in the excited state changes toward the region of higher R-value, and the wavelet conversion of its phase information is sensitive to the change of bond length. The increase in bond length may lead to changes in the different scattering paths as well as an increase in disorder, which further induces the dispersion of the signal in R-space\u003csup\u003e\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e,\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e\u003c/sup\u003e. The increase in disorder is often accompanied by a lower intensity of the main peak in R-space, which has been shown in EAXFS (Figs.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eg-k)\u003csup\u003e39\u003c/sup\u003e. It further confirmed the identification of monodisperse Cu atoms in Cu SAs@MoS\u003csub\u003e2\u003c/sub\u003e and the activation state of Cu SAs under light. X-ray photoelectron spectroscopy (XPS) was performed to elucidate the chemical configuration of the catalyst (Supplementary Fig. S11a). The Mo 3d\u003csub\u003e5/2\u003c/sub\u003e and Mo 3d\u003csub\u003e3/2\u003c/sub\u003e peaks at binding energies of 231.94 eV and 228.41 eV can be indexed to the 2H MoS\u003csub\u003e2\u003c/sub\u003e (Supplementary Fig. S11b), while the peaks at 230.65 eV and 227.39 eV were attributed to Mo 3d\u003csub\u003e5/2\u003c/sub\u003e and Mo 3d\u003csub\u003e3/2\u003c/sub\u003e of 1T MoS\u003csub\u003e2\u003c/sub\u003e\u003csup\u003e40\u003c/sup\u003e. The XPS spectra at 2p signal of S shows similar results, which also clearly demonstrated the coexistence of 2H-MoS\u003csub\u003e2\u003c/sub\u003e and 1T-MoS\u003csub\u003e2\u003c/sub\u003e (Supplementary Fig. S11c). Accordingly, the contents of 1T and 2H phases can be estimated to be 57% and 43%, respectively\u003csup\u003e\u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e41\u003c/span\u003e\u003c/sup\u003e. From the 2p\u003csub\u003e2/3\u003c/sub\u003e spectra of Cu, Cu\u0026minus;S species (at 931.15 eV) can be observed (Supplementary Fig. S11d)\u003csup\u003e\u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e42\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003ePMEC-NORR performances in H-type cell\u003c/h3\u003e\n\u003cp\u003eThe photocurrent response was evaluated. As displayed in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ea, Cu SAs@MoS\u003csub\u003e2\u003c/sub\u003e showed 20 uA cm\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e increased reduction current response with light on, indicating a photo-electron response at under this circumstance. The introduced light onto Cu SAs also leads to the emergence of localized energy levels on the surface of the material,\u003csup\u003e43\u003c/sup\u003e which affects the physical structure such as mentioned Cu\u0026minus;S bonds, the local electronic structure determine the catalytic Cu. A gentle peak to a sharp peak from substrate MoS\u003csub\u003e2\u003c/sub\u003e, the, illustrate the modified electron-transfer ability\u003csup\u003e\u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e44\u003c/span\u003e\u003c/sup\u003e. Figs. S12 a and b show the UV-Vis spectra and tauc plots of Cu SAs@MoS\u003csub\u003e2\u003c/sub\u003e and MoS\u003csub\u003e2\u003c/sub\u003e, respectively. It can be observed that Cu SAs on MoS\u003csub\u003e2\u003c/sub\u003e were almost exhibiting virtually unchanged bandgap width and light absorption.\u003c/p\u003e \u003cp\u003eTo verify the catalytic performances of Cu SAs@MoS\u003csub\u003e2\u003c/sub\u003e under synergistic photo and electric fields, NORR tests were performed in 0.5 M Na\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e electrolyte using an air-tight H-type cell. Figure\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eb shows the linear sweep voltammetry (LSV) curves of Cu SAs@MoS\u003csub\u003e2\u003c/sub\u003e under various conditions. A significantly higher current density was achieved with NO saturated electrolyte than pure Ar saturated electrolyte under both dark and light conditions, implying the occurrence of NORR. Moreover, it also clearly shows that the visible light irradiation can obviously promote the catalytic reduction speed of NO. The Tafel slope of Cu SAs@MoS\u003csub\u003e2\u003c/sub\u003e under light conditions is estimated to be only 35.71 mV dec\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ec), which is significantly lower than that measured under dark condition (54.03 mV dec\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e). These results demonstrate that the light irradiation effectively accelerated the NORR kinetics as expected. Besides, this Cu SAs@MoS\u003csub\u003e2\u003c/sub\u003e catalyst gives much faster reaction kinetics than pure MoS\u003csub\u003e2\u003c/sub\u003e (62.85 mV dec\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e under light and 62.85 mV dec\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e under dark, Supplementary Fig. S13).\u003c/p\u003e \u003cp\u003eThe colorimetric methods are used to quantify the liquid products (Supplementary Figs. S14 and S15), and the gas chromatography is adopted for gas products detection. The potential-dependent PMEC-NORR performances over Cu SAs@MoS\u003csub\u003e2\u003c/sub\u003e was investigated in Figs.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ed and e. Considerable NH\u003csub\u003e3\u003c/sub\u003e yield and FE were achieved at -0.3 V vs RHE, which is significantly superior than that of EC-NORR without light. Only small amount of N\u003csub\u003e2\u003c/sub\u003eH\u003csub\u003e4\u003c/sub\u003e and N\u003csub\u003e2\u003c/sub\u003e were detected as byproducts (Supplementary Fig. S16), which is quite normal in NORR\u003csup\u003e\u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e45\u003c/span\u003e\u003c/sup\u003e. The alternating PMEC tests with and without NO (Supplementary Fig. S17), combination optimum-potential PMEC for 1 h in Ar-saturated electrolyte (Supplementary Fig. S18) and open-circuit voltage (OCP) in NO-saturated electrolyte (Supplementary Fig. S19) are sufficient to confirm that the PMEC-NORR products (NH\u003csub\u003e3\u003c/sub\u003e) are all derived from the reduction of NO. The best NH\u003csub\u003e3\u003c/sub\u003e yield and FE were obtained at -0.3 V due to the synergistic catalytic effect under light and electro fields. Subsequent long-term test was also carried out at optimal \u0026minus;\u0026thinsp;0.3 V vs. RHE (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ef). It demonstrated that Cu SAs@MoS\u003csub\u003e2\u003c/sub\u003e has excellent stability up to 10 h with no noticeable decline in its performance with this H-type cell (average yield of 62.76 \u0026micro;mol h\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e mg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e and FE of 90%).\u003c/p\u003e \u003cp\u003eAs shown in Figs.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eg and h, in case of Cu SAs@MoS\u003csub\u003e2\u003c/sub\u003e is used as catalyst, the NH\u003csub\u003e3\u003c/sub\u003e yield is 60.55 \u0026micro;mol h\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e mg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e and FE is estimated to be 90.66% at -0.3 V vs RHE in the PMEC-NORR. As comparison, MoS\u003csub\u003e2\u003c/sub\u003e and Cu NWs samples were also tested under the same condition, delivering much lower NH\u003csub\u003e3\u003c/sub\u003e yields (17.11 and 25.63 \u0026micro;mol h\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e mg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e) and inferior FE (36.24% and 32.65%). This result demonstrated that Cu SAs loaded on MoS\u003csub\u003e2\u003c/sub\u003e provided enhanced catalytic activity of NORR compared to metal Cu NWs and pure MoS\u003csub\u003e2\u003c/sub\u003e samples. To further demonstrate the effectiveness of the light assistance in catalyzing the NORR, subsequent EC-NORR and PC-NORR tests were also performed. For EC-NORR, Cu SAs@MoS\u003csub\u003e2\u003c/sub\u003e exhibited an obvious decreased NH\u003csub\u003e3\u003c/sub\u003e yield of 35.61 \u0026micro;mol h\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e mg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e and a lower FE of 80.26% without the light coupled. MoS\u003csub\u003e2\u003c/sub\u003e also displayed a similar decrease in NH\u003csub\u003e3\u003c/sub\u003e yield and FE in the absence of light irradiation. While Cu NWs showed similar performances in EC-NORR to its PMEC condition, because it is insensitive to light irradiation. A negligible NH\u003csub\u003e3\u003c/sub\u003e yield was detected under PC condition for all these samples, indicating that pure light irradiation cannot drive the NORR under this condition. Only with negative potential or current, process could be activated and further enhanced by introducing light-modulation.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e\n\u003ch3\u003eClarification of the catalytic mechanisms\u003c/h3\u003e\n\u003cp\u003eTo further investigate the role of Cu SAs and the effect of light irritation for the PMEC reaction, subsequent density functional theory (DFT) was performed. As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ea, the projected density of states of the Cu 3d orbitals at ground state is rarely available above the Fermi level in the energy range from 0 to 4 eV, whereas under light illumination a clear peak between 0 and 4 eV occurs, suggesting that a reduced state into the Cu 3d manifold. Figure\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eb complementary charge-density difference plots in the panels show that under light illumination, the integrated electron population in the Cu site increases from 0.14 e\u003csup\u003e\u0026minus;\u003c/sup\u003e in dark to 0.19 e\u003csup\u003e\u0026minus;\u003c/sup\u003e, suggesting that Cu SAs transitions into a localized electron trap. It is confirmed that this a electron accumulation at the Cu SAs site will enhance the activation of adsorbed NO by providing more electron for driving the whole NORR reaction from adsorbing NO and weakening N-O bond to the successive hydrogenation steps, thus facilitating the NORR process\u003csup\u003e\u003cspan additionalcitationids=\"CR47 CR48\" citationid=\"CR46\" class=\"CitationRef\"\u003e46\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR49\" class=\"CitationRef\"\u003e49\u003c/span\u003e\u003c/sup\u003e. The theoretical optimized adsorption configurations of Cu SAs@MoS\u003csub\u003e2\u003c/sub\u003e and MoS\u003csub\u003e2\u003c/sub\u003e towards NO molecules and corresponding intermediates (Supplementary Figs. S20-23), as well as the corresponding Gibbs free energy (ΔG) are calculated using DFT. We proposed a possible reaction pathway for PMEC-NORR on Cu SAs@MoS\u003csub\u003e2\u003c/sub\u003e catalyst: *NO \u0026rarr; *NHO \u0026rarr; *NHOH \u0026rarr; *NH\u003csub\u003e2\u003c/sub\u003eOH \u0026rarr; *NH\u003csub\u003e2\u003c/sub\u003e \u0026rarr; *NH\u003csub\u003e3\u003c/sub\u003e (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ec). The hydrogenation of *NO to *NHO intermediates is considered as the RDS in this reaction. The ΔG for the production of *NHO intermediates on Cu SAs@MoS\u003csub\u003e2\u003c/sub\u003e catalyst is -1.3 eV, which is much more negative than that on MoS\u003csub\u003e2\u003c/sub\u003e catalyst, which is -0.15 eV (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ed), which explains the significantly enhanced catalytic performance of the Cu SAs@MoS\u003csub\u003e2\u003c/sub\u003e material.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eTo gain more insight of this PMEC-NORR, the operando photo-electrochemical attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) was utilized to monitor the absorbed intermediates produced during the reaction. In the time-dependent operando photo-electrochemical ATR-FTIR spectra, NO molecules are primarily adsorbed on the surface of Cu SAs@MoS\u003csub\u003e2\u003c/sub\u003e in a vertical vibrational mode with peaks at 1710 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ea) under light illumination\u003csup\u003e\u003cspan citationid=\"CR50\" class=\"CitationRef\"\u003e50\u003c/span\u003e,\u003cspan citationid=\"CR51\" class=\"CitationRef\"\u003e51\u003c/span\u003e\u003c/sup\u003e. The signal intensity is evidently higher than that recorded on MoS\u003csub\u003e2\u003c/sub\u003e material (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eb), indicating that Cu SAs facilitates the alteration of the NO dipole moment, making it more favorable for activation into *NO. The hydrogenated intermediate *NHO appears at 1524 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, suggesting that the first hydrogenation step occurs at the nitrogen end of NO molecule\u003csup\u003e\u003cspan citationid=\"CR50\" class=\"CitationRef\"\u003e50\u003c/span\u003e\u003c/sup\u003e. As the reaction goes on, the *NH\u003csub\u003e2\u003c/sub\u003e hydrogenated intermediate is observed at 1336 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e and 1506 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, and a strong *NH\u003csub\u003ex\u003c/sub\u003e peak emerges at 1457 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e. The increasing intensity of these peaks along with reaction time indicates the accumulation of hydrogenated species on the surface of this catalyst. The potential-dependent operando photo-electrochemical ATR-FTIR spectra are also measured. Supplementary Fig. S24 shows that *NO, *NHO and *NH\u003csub\u003ex\u003c/sub\u003e intermediates on Cu SAs@MoS\u003csub\u003e2\u003c/sub\u003e become evident at a quite positive potential of +\u0026thinsp;0.1 V vs RHE, while MoS\u003csub\u003e2\u003c/sub\u003e requires a more negative potential of -0.1 V vs. RHE. This result indicates that Cu SAs@MoS\u003csub\u003e2\u003c/sub\u003e has lower overpotential than MoS\u003csub\u003e2\u003c/sub\u003e during the PMEC-NORR due to the active Cu SAs sites, which is in agreement with the PMEC performances. In Supplementary Fig. S25, we further explored the adsorption of *H on the surfaces of the catalysts by operando photo-electrochemical ATR-FTIR spectra depending on time and potential. It can be observed that Cu SAs@MoS\u003csub\u003e2\u003c/sub\u003e has strong *H adsorption peaks at 1965\u0026ndash;1967 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e (Supplementary Figs. S25 a and b), which is more favorable for the hydrogenation of NO molecules to produce NH\u003csub\u003e3\u003c/sub\u003e product other than the combination of *H to produce H\u003csub\u003e2\u003c/sub\u003e\u003csup\u003e52,53\u003c/sup\u003e. As comparison, MoS\u003csub\u003e2\u003c/sub\u003e shows much lower adsorption towards *H even at negative potential, which may lead to competitive H\u003csub\u003e2\u003c/sub\u003e evolution (Supplementary Figs. S25 c and d)\u003csup\u003e54\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eAs shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ec, operando ATR-FTIR measurements under a constant current of 0.5 mA revealed that the characteristic bands at 1168 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e and 1140 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, assignable to NO⁻ and *NOH intermediates, respectively, reproducibly exhibited higher intensities upon PMEC compared to the EC (repeated four times). This observation indicates that light irritation promotes hydrogenation at the O-terminus of NO, thereby facilitating the formation of *NOH species. To further probe the hydrogen radical dynamics, DMPO-trapped EPR experiments were performed. As shown in Figs.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ed and e, Cu SAs@MoS\u003csub\u003e2\u003c/sub\u003e displayed a significantly stronger *H\u003cem\u003e-\u003c/em\u003erelated signal than MoS\u003csub\u003e2\u003c/sub\u003e, and the *H signal was further enhanced under light irradiation, evidencing the light-driven generation of reactive hydrogen species. Moreover, operando EPR under continuous NO flow (Figs.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ef and g) revealed distinct time-dependent behaviors, for MoS\u003csub\u003e2\u003c/sub\u003e, the *H signal persisted even after 5 min, whereas for Cu SAs@MoS\u003csub\u003e2\u003c/sub\u003e, the *H species were completely consumed by this time. These results demonstrate that Cu SAs@MoS\u003csub\u003e2\u003c/sub\u003e not only increases the availability of *H but also accelerates its consumption in NO hydrogenation, thus providing direct evidence that light assists the electrocatalytic process by modulating both the hydrogenation pathway and *H dynamics.\u003c/p\u003e\n\u003ch3\u003ePMEC-NORR performances in flow cell\u003c/h3\u003e\n\u003cp\u003eSince the low solubility of diluted NO in aqueous electrolyte, gas-liquid-solid three-phase flow cell is considered as potential candidates for the practical NORR. It directly overcomes the NO's low solubility by enabling intense interaction between all reactant phases at the catalyst surface while ensuring stable, continuous operation. Thus, an PMEC-flow cell was designed in this work to evaluate the continuous NORR performances for the first time. As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ea, the cathode chamber is equipped with a quartz light window of 1\u0026times;1 cm\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e area for light illumination, and the NO gas and electrolyte flow into the chamber from the two separated inlets. Ag/AgCl and Pt electrodes were used as reference and counter electrode, respectively. Linear sweep voltammetry (LSV) curves of the PMEC-flow cell can be clearly observed that the introduction of photo field provides additional current density (Supplementary Fig. S26). The PMEC-flow cell performances were evaluated at different potentials as shown in Figs.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003eb, c and Supplementary Fig. S27a. The NH\u003csub\u003e3\u003c/sub\u003e yield of 254.8 \u0026micro;mol h\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e mg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e at -0.4 V vs RHE with FE of 81.86% was achieved. The gas flow rate was optimized, showing best activity with 30 sccm due to the equilibrium adsorption on the surface of catalysts (Supplementary Figs. S28a and b). Subsequent constant-current PMEC-NORR was performed at gas flow rate of 30 sccm with current density in the range of 25\u0026ndash;200 mA cm\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e. An ultra-high NH\u003csub\u003e3\u003c/sub\u003e yield of 3228 \u0026micro;mol h\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e mg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e as well as an excellent FE of 86.53% were achieved at a current density of 100 mA cm\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ed and e, Supplementary Fig. S27b, Figs. S28c and d). Compared with the previously reported low concentration EC-NORR performances, this Cu SAs@MoS\u003csub\u003e2\u003c/sub\u003e with PMEC-NORR system showed highest NH\u003csub\u003e3\u003c/sub\u003e yield and FE (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ef and Supplementary Table S3). Moreover, the long-term durability up to 45 h was achieved at current density of 100 mA cm\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e, showing excellent stability, which is also promising for the industrial PMEC-NORR to produce NH\u003csub\u003e3\u003c/sub\u003e by flow cells (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003eg).\u003c/p\u003e "},{"header":"Discussion","content":"\u003cp\u003eIntuitively, obtaining high yield and high Faradaic efficiency simultaneously is difficult under low-concentration conditions. They are often considered as a trade-off relationship. However, by simply focusing on the design of the Cu coordination environment, this trade-off was seemly broken. We developed an advanced Cu single-atom catalyst to promote the electrochemical conversion of NO to NH\u003csub\u003e3\u003c/sub\u003e. The efficient NORR catalyst, Cu SAs@MoS\u003csub\u003e2\u003c/sub\u003e, was synthesized via a microwave-assisted method that enables the atomic dispersion of Cu sites on a mixed-phase MoS\u003csub\u003e2\u003c/sub\u003e substrate. Combined experimental characterizations and DFT calculations reveal that light irradiation modulates the local Cu\u0026ndash;S coordination environment, thereby accelerating NORR kinetics through enhanced NO activation and a significantly reduced energy barrier for the rate-determining hydrogenation step. Benefiting from this photo-modulated electronic reconstruction, the PMEC flow cell achieves an ultra-high NH\u003csub\u003e3\u003c/sub\u003e yield of 3228 \u0026micro;mol h\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e mg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e and FE of 86.53% at 100 mA cm\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e. Such a high conversion rate in a low-concentration environment has not been reported before. This work demonstrates the strong potential of photo-modulated electrocatalysis for efficient NO valorization under practical conditions. The process mirrors the logic of natural photosynthesis\u0026mdash;using light as a precise tool to activate and convert abundant but inert molecules (N\u003csub\u003e2\u003c/sub\u003e in nature) into valuable fertilizers. This photo-modulated electrocatalysis strategy presents a compelling pathway for the sustainable upcycling of low-concentration pollutants, including NO\u003csub\u003ex\u003c/sub\u003e, CO\u003csub\u003e2\u003c/sub\u003e and nitrates, moving us closer to smart, adaptive catalytic systems for closing anthropogenic chemical loops. Ultimately, this \u0026ldquo;artificial photo-electro nitrogen fixation\u0026rdquo; paradigm holds promise as a smart platform contributing to the realization of sustainable carbon- or nitrogen-negative chemical cycles and steering energy and environmental catalysis toward a new avenue of precision-controlled molecular transformation and circular economy.\u003c/p\u003e "},{"header":"Methods","content":"\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003cdiv id=\"Sec9\" class=\"Section3\"\u003e \u003ch2\u003eMaterials\u003c/h2\u003e \u003cp\u003eCarbon papers (HCP020N, thickness: 0.19\u0026thinsp;\u0026plusmn;\u0026thinsp;0.01 mm) were purchased from Hesen company (Shanghai, China). Sodium hydroxide (NaOH AR) was purchased from Richjoint. hydrochloric acid (HCl) and sulphury acid (H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e) were purchased from Sinopharm Chemical Reagent Co. Ltd., methanol (CH\u003csub\u003e3\u003c/sub\u003eOH), isopropanol (C\u003csub\u003e3\u003c/sub\u003eH\u003csub\u003e8\u003c/sub\u003eO), Cu(NO\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e\u0026middot;3H\u003csub\u003e2\u003c/sub\u003eO, N\u003csub\u003e2\u003c/sub\u003eH\u003csub\u003e4\u003c/sub\u003e, ethylenediamine (98%), thiourea (99%), ammonium chloride (NH\u003csub\u003e4\u003c/sub\u003eCl), ethanol (C\u003csub\u003e2\u003c/sub\u003eH\u003csub\u003e5\u003c/sub\u003eOH), salicylic acid (C\u003csub\u003e7\u003c/sub\u003eH\u003csub\u003e6\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e), trisodium citrate dihydrate (C\u003csub\u003e6\u003c/sub\u003eH\u003csub\u003e5\u003c/sub\u003eNa\u003csub\u003e3\u003c/sub\u003eO\u003csub\u003e7\u003c/sub\u003e\u0026middot;2H\u003csub\u003e2\u003c/sub\u003eO, AR), p-dimethylaminobenzaldehyde (C\u003csub\u003e9\u003c/sub\u003eH\u003csub\u003e11\u003c/sub\u003eNO), sodium ferrocyanide nitrite dihydrate (C\u003csub\u003e5\u003c/sub\u003eFeN\u003csub\u003e6\u003c/sub\u003eNaO\u0026middot;2H\u003csub\u003e2\u003c/sub\u003eO), sodium hypochlorite (NaClO), ammonium molybdate ((NH)\u003csub\u003e6\u003c/sub\u003eMo\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e24\u003c/sub\u003e) (99%) were purchased from Aladdin Biochemical Technology Co., Ltd.\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e\n\u003ch3\u003eSynthesis of Cu NWs\u003c/h3\u003e\n\u003cp\u003eCu NWs were synthesized based on previous reports\u003csup\u003e\u003cspan citationid=\"CR55\" class=\"CitationRef\"\u003e55\u003c/span\u003e\u003c/sup\u003e. Specifically, 500 g of 85% aqueous NaOH solution was dissolved in 833 mL of deionized water under strong stirring, followed by the slow addition of 41.5 mL of a 0.1 M Cu(NO\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e aqueous solution. After stirring for 40 minutes, 6.225 mL of ethylenediamine (H\u003csub\u003e2\u003c/sub\u003eNCH\u003csub\u003e2\u003c/sub\u003eCH\u003csub\u003e2\u003c/sub\u003eNH\u003csub\u003e2\u003c/sub\u003e) solution and 1.037 mL of 35% N\u003csub\u003e2\u003c/sub\u003eH\u003csub\u003e4\u003c/sub\u003e aqueous solution were added. The mixture was transferred to a desiccator and heated at 80\u0026deg;C for 3 hours. Afterwards, the obtained copper nanowires were washed repeatedly with ethanol to remove the residual solvent and then sealed in ethanol.\u003c/p\u003e \u003cdiv id=\"Sec11\" class=\"Section2\"\u003e \u003ch2\u003eSynthesis of Cu SAs@MoS\u003csub\u003e2\u003c/sub\u003e\u003c/h2\u003e \u003cp\u003eCu SAs@MoS\u003csub\u003e2\u003c/sub\u003e was prepared by modified microwave-assisted method\u003csup\u003e\u003cspan citationid=\"CR56\" class=\"CitationRef\"\u003e56\u003c/span\u003e\u003c/sup\u003e. Typically, 2 mmol of Cu NWs was dispersed in 20 mL of deionized water by sonication for 2 h, and then 0.5 mmol (NH)\u003csub\u003e6\u003c/sub\u003eMo\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e24\u003c/sub\u003e (99%, Macklin) and 30 mmol thiourea (99%, Aladdin) were immediately added to the solution and dispersed well by sonication for 1 h. The well-mixed reactants were transferred to a quartz vessel equipped with a microwave system (Ethos TC, 1300 W). The reaction was heated for 20 min at 180 ℃ with a rising rate of 15\u0026deg;C min\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e and an argon pressure of 35 bar. After cooling to room temperature, the product was thoroughly washed three times with deionized water and ethanol, respectively. Black powder was obtained after vacuum drying at 80\u0026deg;C for 12 h and denoted as Cu SAs@MoS\u003csub\u003e2\u003c/sub\u003e.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec12\" class=\"Section2\"\u003e \u003ch2\u003eSynthesis of MoS\u003csub\u003e2\u003c/sub\u003e\u003c/h2\u003e \u003cp\u003ePure MoS\u003csub\u003e2\u003c/sub\u003e sample was synthesized by the similar method with Cu SAs@MoS\u003csub\u003e2\u003c/sub\u003e, except the addition of Cu NWs.\u003c/p\u003e \u003cp\u003e \u003cb\u003eXAFS and\u003c/b\u003e \u003cb\u003ein situ\u003c/b\u003e \u003cb\u003eXAFS experimental details\u003c/b\u003e\u003c/p\u003e \u003cp\u003eThe X-ray absorption data at the Cu K-edge of the samples were measured at room temperature in the fluorescent mode with the large solid angle Lytle detector at beamline BL14W1 of the Shanghai Synchrotron Radiation Facility (SSRF), China. The station was operated with a Si (111) double crystal monochromator. During the measurement, the storage ring was operated at the energy of 3.5 GeV and a current of 200 mA (top-up). \u003cem\u003eIn-situ\u003c/em\u003e XAFS test was carried out on the Cu SAs@MoS\u003csub\u003e2\u003c/sub\u003e under Xe lamp irradiation. The photon energy was calibrated with the first inflection point in Cu K-edge of Cu metal foil. The finely grounded sample powder was coated on the adhesive tape for XAFS measurements. Athena and Artemis codes were used to extract the data and fit the profiles.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec13\" class=\"Section2\"\u003e \u003ch2\u003ePhysicochemical characterizations\u003c/h2\u003e \u003cp\u003eFESEM images were observed on field-emission scanning electron microscope (SEM, HITACHI, S-4800) and transmission electron microscopy (TEM) images were collected at an acceleration voltage of 200 kV (TEM, JEOL JEM-2100F). Powder Xray diffraction (XRD) was conducted on a Bruker D8 Advance X-ray powder diffractometer using Cu-Kα radiation (λ\u0026thinsp;=\u0026thinsp;1.54 \u0026Aring;). The Co contents were estimated by Inductively Coupled Plasma-Optical Emission Spectrometry (ICP-OES, ICPE-9000, Shimadzu, Japan). XPS was measured by Thermo Scientific K-Alpha All the binding energy values were calibrated by using C1s\u0026thinsp;=\u0026thinsp;284.6 eV as a reference. The UV-vis diffuse reflectance spectra (DRS) were obtained on a UV-vis spectrophotometer (UV-vis DRS, Shimadzu UV-2450). The Cu K-edge X-ray absorption fine structure spectroscopy (XAFS) was measured at the Shanghai Synchrotron Radiation Facility (SSRF), China. \u003cem\u003eIn situ\u003c/em\u003e attenuated total reflection Fourier transform infrared (ATR-FTIR) spectra were measured on a Thermo Scientific Nicolet 6700 spectrometer equipped with a PIKE VeeMAX III variable angle ATR sampling accessory.1H nuclear magnetic resonance (NMR) spectra were conducted on a Bruker Avance III HD 600 MHz spectrometer.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec14\" class=\"Section2\"\u003e \u003ch2\u003ePhoto modulated-electrochemical measurements\u003c/h2\u003e \u003cp\u003eThe photo switched electrocatalytic NO reduction reaction (PMEC-NORR) was carried out in a quartz H-type electrolytic reactor equipped with a light window. 40 mL 0.5 M Na\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e solution was filled in each chamber as electrolyte. Nafion 117 membrane was first boiled in boiling water for 1 h, followed by treatment with H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e (5 wt%) at 80\u0026deg;C for 1 h. Subsequent protonation of the membranes was carried out using 0.5 M H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e at 80\u0026deg;C for 3 h to maintain the temperature after protonation in water for a final treatment of 6 h. Then, it was used to separate cathode and anode chambers. In order to avoid unwanted formation of nitrogen dioxide (NO\u003csub\u003e2\u003c/sub\u003e) due to easy oxidation of NO by O\u003csub\u003e2\u003c/sub\u003e, high-purity Ar (99.99%) was passed through the electrolyze for 30 min to remove residual oxygen.\u003c/p\u003e \u003cp\u003eAll photoelectrochemical tests were performed using a CHI 760E photoelectrochemical test using a three-electrode system. Pt sheet and Ag/AgCl (saturated KCl electrolyte) were used of counter and reference electrodes, respectively. A carbon paper (1\u0026times;1 cm\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e) loaded with 1 mg catalyst was used as working electrode in the H-type cell. In the flow cell, the loading was decreased to 0.20 mg cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e. Xenon lamp (150 W) equipped with a UV cut filter to cut off lights (λ\u0026thinsp;\u0026lt;\u0026thinsp;420 nm) was used as light source. All potentials were referenced against the reversible hydrogen electrode (RHE) based on the Nernst equation (E\u003csub\u003eRHE\u003c/sub\u003e = E\u003csub\u003eAg/AgCl\u003c/sub\u003e + 0.059 \u0026times; pH\u0026thinsp;+\u0026thinsp;0.197). The linear sweep voltammetry (LSV) tests were all performed at a scanning speed of 5 mV s\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e. For evaluation of performances of PMEC-NORR over these catalysts, the chronoamperometry (CA) tests were conducted in NO-saturated 0.5 M Na\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e electrolyte using a NO/Ar gas mixture (10% NO, 30 sccm) continuously vented to the cathode of the electrolytic cell, with continuous stirring (at 500 rpm). 4 M KOH and acidic KMnO\u003csub\u003e4\u003c/sub\u003e solutions were used for NO tail gas absorption. The gas flow rate was controlled by the mass flow controllers (Beijing I Know Meter Science and Technology Ltd.).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec15\" class=\"Section2\"\u003e \u003ch2\u003eProducts detection\u003c/h2\u003e \u003cdiv id=\"Sec16\" class=\"Section3\"\u003e \u003ch2\u003eDetermination of NH\u003csub\u003e3\u003c/sub\u003e\u003c/h2\u003e \u003cp\u003eThe amount of NH\u003csub\u003e3\u003c/sub\u003e was determined by colorimetry using the indophenol blue method. A certain amount of electrolyte was taken out from the electrolytic cell and diluted to 2 mL to the detection range. Then, 2 mL of a 1 M NaOH solution that contained salicylic acid and sodium citrate was added. Then, 1 mL of 0.05 M NaClO and 0.2 mL of 1 wt% C\u003csub\u003e5\u003c/sub\u003eFeN\u003csub\u003e6\u003c/sub\u003eNa\u003csub\u003e2\u003c/sub\u003eO\u0026middot;2H\u003csub\u003e2\u003c/sub\u003eO were added to the above solution. After standing for 2 h at room temperature, the UV-Vis absorption spectrum was measured. The concentration of NH\u003csub\u003e3\u003c/sub\u003e was determined using the absorbance at a wavelength of 660 nm. The concentration-absorbance curve was calibrated using a series of standard NH\u003csub\u003e4\u003c/sub\u003eCl solutions. The fitting curve (y\u0026thinsp;=\u0026thinsp;0.119x\u0026thinsp;+\u0026thinsp;0.0014, R\u003csup\u003e2\u003c/sup\u003e\u0026thinsp;=\u0026thinsp;0.999) showed good linear relation of absorbance value with NH\u003csub\u003e3\u003c/sub\u003e concentrations.\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv id=\"Sec17\" class=\"Section2\"\u003e \u003ch2\u003eDetermination of N\u003csub\u003e2\u003c/sub\u003eH\u003csub\u003e4\u003c/sub\u003e\u003c/h2\u003e \u003cp\u003eThe N\u003csub\u003e2\u003c/sub\u003eH\u003csub\u003e4\u003c/sub\u003e presented in the electrolyte was estimated by Watt and Chrisp method. Color reagent includes C\u003csub\u003e9\u003c/sub\u003eH\u003csub\u003e11\u003c/sub\u003eNO (5.99 g), HCl (concentrated, 30 mL) and ethanol (300 mL). 1 mL above color reagent and 1 mL electrolyte were mixed and stirred 15 min at room temperature. The concentration of N\u003csub\u003e2\u003c/sub\u003eH\u003csub\u003e4\u003c/sub\u003e was determined using the absorbance at a wavelength of 455 nm. The absorbance curves were calibrated using standard N\u003csub\u003e2\u003c/sub\u003eH\u003csub\u003e4\u003c/sub\u003e solution with a series of concentrations.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec18\" class=\"Section2\"\u003e \u003ch2\u003eDetermination of NO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e\u0026minus;\u003c/sup\u003e\u003c/h2\u003e \u003cp\u003eFirstly, a certain amount of electrolyte was taken out from the electrolytic cell and diluted to 5 mL to the detection range. Then, 0.1 mL 1 M HCl and 0.01 mL 0.8 wt% sulfamic acid solution were added into the aforementioned solution. The absorption spectrum was measured using a UV-Vis spectrophotometer and the absorption intensities at a wavelength of 220 nm and 275 nm were recorded. The final absorbance value was calculated by this equation: A\u0026thinsp;=\u0026thinsp;A\u003csub\u003e220\u003c/sub\u003e nm \u0026ndash; 2A\u003csub\u003e275\u003c/sub\u003e nm. The concentration-absorbance curve was calibrated using a series of standard NaNO\u003csub\u003e3\u003c/sub\u003e solutions and the NaNO\u003csub\u003e3\u003c/sub\u003e crystal was dried at 110 \u0026ordm;C for 2 h in advance.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec19\" class=\"Section2\"\u003e \u003ch2\u003eDetermination of H\u003csub\u003e2\u003c/sub\u003e and N\u003csub\u003e2\u003c/sub\u003e\u003c/h2\u003e \u003cp\u003eH\u003csub\u003e2\u003c/sub\u003e and N\u003csub\u003e2\u003c/sub\u003e was monitored by gas chromatography (GC).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec20\" class=\"Section2\"\u003e \u003ch2\u003eDetermining FE and NH\u003csub\u003e3\u003c/sub\u003e yield\u003c/h2\u003e \u003cp\u003eThe FE for NH\u003csub\u003e3\u003c/sub\u003e photoelectrosynthesis is defined as the ratio of the charge utilized for NH\u003csub\u003e3\u003c/sub\u003e production to the total charge passing through the electrode during electrolysis. This can be expressed mathematically using the following formula:\u003c/p\u003e \u003cp\u003eFE\u0026thinsp;=\u0026thinsp;n \u0026times; F \u0026times; c \u0026times; V / (M \u0026times; Q) (1)\u003c/p\u003e \u003cp\u003eThe NH\u003csub\u003e3\u003c/sub\u003e yield was calculated using the following equation:\u003c/p\u003e \u003cp\u003eNH\u003csub\u003e3\u003c/sub\u003e yield\u0026thinsp;=\u0026thinsp;c \u0026times; V / (17 \u0026times; t \u0026times; S) (2)\u003c/p\u003e \u003cp\u003eWhere n is the number of electrons was needed to produce one product molecule; F is Faraday constant (96485 C mol\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e); c is the measured mass concentration of product; V is the volume of the cathodic reaction electrolyte (40 mL); M is relative molecular mass of specific product; Q is the quantity of applied charge/electricity; t is the time for which the potential was applied (1 h); S is the geometric area of the working electrode (1 cm\u003csup\u003e2\u003c/sup\u003e).\u003c/p\u003e \u003cp\u003e \u003cb\u003eIn situ\u003c/b\u003e \u003cb\u003eATR-FTIR test\u003c/b\u003e\u003c/p\u003e \u003cp\u003eThe crystalline silicon substrates were covered with a gold film to increase the reflected signals. The catalyst-loaded gold film supported by crystalline silicon, Pt, and Ag/AgCl electrodes served as the working electrode, counter electrode, and reference electrode, respectively. The H-shaped electrolytic cell was made of quartz. The light sources were Xenon lamp (150 W) equipped with a UV cut filter to cut off lights (λ\u0026thinsp;\u0026lt;\u0026thinsp;420 nm) was used as light source.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec21\" class=\"Section2\"\u003e \u003ch2\u003eComputational details\u003c/h2\u003e \u003cp\u003eThe spin-polarized density functional theory (DFT) calculations have been conducted on Vienna ab-initio simulation package (VASP)\u003csup\u003e\u003cspan citationid=\"CR57\" class=\"CitationRef\"\u003e57\u003c/span\u003e,\u003cspan citationid=\"CR58\" class=\"CitationRef\"\u003e58\u003c/span\u003e\u003c/sup\u003e to study the catalytic process of prepared catalysts. The generalized gradient approximation proposed by Perdew-Burke-Ernzerhof (PBE) is selected for the exchange-correlation potential\u003csup\u003e\u003cspan citationid=\"CR59\" class=\"CitationRef\"\u003e59\u003c/span\u003e,\u003cspan citationid=\"CR60\" class=\"CitationRef\"\u003e60\u003c/span\u003e\u003c/sup\u003e. The cut-off energy for plane wave is set to 500 eV. The energy criterion is set to 10\u003csup\u003e\u0026minus;\u0026thinsp;5\u003c/sup\u003e eV in the iterative solution of the Kohn-Sham equation. To avoid interlaminar interactions, a vacuum spacing of 20 \u0026Aring; is applied perpendicular to the slab. The Brillouin zone integration is performed using a 3\u0026times;3\u0026times;1 k-mesh. All the structures are relaxed until the residual forces on the atoms have declined to less than 0.02 eV/\u0026Aring;. DFT-D3 method\u003csup\u003e\u003cspan citationid=\"CR61\" class=\"CitationRef\"\u003e61\u003c/span\u003e\u003c/sup\u003e was used to correct the influence of van der Waals interactions.\u003c/p\u003e \u003cp\u003eTwo layers of 1T-MoS\u003csub\u003e2\u003c/sub\u003e (001) facets have been cleaved with a vacuum of 15 \u0026Aring; to build the slab models. The adsorption energy (E\u003csub\u003eads\u003c/sub\u003e) has been calculated using formula 3:\u003cdiv id=\"Equa\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equa\" name=\"EquationSource\"\u003e\n$$\\:{E}_{ads}={E}_{total}-{E}_{substrate}-{E}_{adsorbate}\\:\\:\\:\\:\\left(3\\right)$$\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e \u003cp\u003eThe E\u003csub\u003etotal\u003c/sub\u003e, E\u003csub\u003esubstrate\u003c/sub\u003e and E\u003csub\u003eadsorbate\u003c/sub\u003e represent the energy of adsorption structure, substrate and adsorbate, respectively. The free energies have been calculated using the following formula 4:\u003cdiv id=\"Equb\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equb\" name=\"EquationSource\"\u003e\n$$\\:G=\\:{E}_{DFT}+ZPE-TS\\:\\:\\:\\:\\left(4\\right)$$\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e \u003cp\u003eThe G, E\u003csub\u003eDFT\u003c/sub\u003e, ZPE and TS represent the free energy, energy from DFT calculations, zero-point energy and entropic contributions, respectively.\u003c/p\u003e \u003c/div\u003e"},{"header":"Declarations","content":"\u003ch2\u003eCompeting interests\u003c/h2\u003e \u003cp\u003eThe authors declare no competing interests.\u003c/p\u003e \u003ch2\u003eAuthor contributions\u003c/h2\u003e \u003cp\u003eX.L. and Z.L. conceived the project, carried out the experiments, analyze the data and wrote the draft of manuscript. S.H. and W.T. carried out the EXAF experiments, theoretical calculation, data analysis and manuscript revision. L. H., L.H., Q.W., S.L., X.W., and T.L. contributed to the experimental synthesis, catalysts characterization and electrochemical measurements. G.L. and H.L. discussed and revised the manuscript. D.Z. and J. L. supervised the project, manuscript preparation and discussion.\u003c/p\u003e\u003ch2\u003eAcknowledgments\u003c/h2\u003e \u003cp\u003eThis work was supported by the National Natural Science Foundation of China (22376142, 22305157, 22236005, 22022608, 22176127), National Key Research and Development Program of China (2020YFA0211004), the Shanghai Engineering Research Center of Green Energy Chemical Engineering (18DZ2254200), and \u0026ldquo;111\u0026rdquo; Innovation and Talent Recruitment Base on Photochemical and Energy Materials (D18020), the Shanghai Government (22010503400, 23520711100, 218014346, 18SG41, YDZX20213100003002) Shanghai Scientific and Technological Innovation Project (21DZ1206300). Yunnan University Collaborative Innovation Center (Qujing Green Photovoltaic Industry Collaborative Innovation Center), Technology Talent and Platform Plan Project of Yunnan Provincial Department of Science and Technology (202305AF150088), Technology Talent and Platform Plan Project of Yunnan Provincial Department of Science and Technology (202405AF140016).\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003ePerry RA, Siebers DL (1986) Rapid reduction of nitrogen oxides in exhaust gas streams. Nature 324:657\u0026ndash;658\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eAnenberg SC et al (2017) Impacts and mitigation of excess diesel-related NO\u003csub\u003ex\u003c/sub\u003e emissions in 11 major vehicle markets. Nature 545:467\u0026ndash;471\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003ePeplow M (2005) Farms spew out nitrogen oxides. 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Phys Rev B 54:11169\u0026ndash;11186\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003ePerdew JP, Burke K, Ernzerhof M (1996) Generalized Gradient Approximation Made Simple. Phys Rev lett 77:3865\u0026ndash;3868\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eKohn W, Sham LJ (1965) Self-Consistent Equations Including Exchange and Correlation Effects. Phys Rev 140:A1133\u0026ndash;A1138\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eGrimme S, Antony J, Ehrlich S, Krieg H (2010) A consistent and accurate Ab initio parametrization of density functional dispersion correction (DFT-D) for the 94 elements H-Pu. J Chem Phys 132:154104\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":true,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Cu single atoms, photo modulated electrocatalysis, NO removal, NO reduction, NH3 synthesis","lastPublishedDoi":"10.21203/rs.3.rs-8346707/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-8346707/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eEfficient electrochemical reduction of nitric oxide (NORR) under practical low-concentration conditions remains challenging due to insufficient NO adsorption, sluggish proton-coupled electron transfer, and severe competition from hydrogen evolution. In this work, a photo-modulated electrocatalysis system was fabricated for driving the reduction of low concentration NO pollutant to NH\u003csub\u003e3\u003c/sub\u003e, based on Cu single atoms (Cu SAs) decorated MoS\u003csub\u003e2\u003c/sub\u003e. The light irradiation induces the Cu SAs active sites switched to a lower valence state with prolonged Cu\u0026minus;S bonds instantaneously, facilitating the adsorption and activation towards NO molecules even at low concentration. As anticipated, a high NH\u003csub\u003e3\u003c/sub\u003e yield up to 3228 \u0026micro;mol h\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e mg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e with a Faradaic efficiency (FE) of 86.53% were achieved in a flow cell at a current density of 100 mA cm\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e. Such NH\u003csub\u003e3\u003c/sub\u003e yield value and FE are much higher than that obtained by the electrocatalysis of NO reduction reaction (NORR) so far. This work demonstrates that rational modulation of the localized coordination structure of single-atom centers can unlock previously inaccessible activity for disposing low-concentration nitrogen-containing pollutants.\u003c/p\u003e","manuscriptTitle":"Efficient Ammonia Production from Nitric Oxide under Real Condition Using Photo-Modulated Cu Single-Atom Catalysts","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-12-23 07:48:03","doi":"10.21203/rs.3.rs-8346707/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"e0184be5-c7dc-4106-8bcb-2971c647ecc1","owner":[],"postedDate":"December 23rd, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[{"id":60044876,"name":"Physical sciences/Chemistry/Environmental chemistry"},{"id":60044877,"name":"Physical sciences/Chemistry/Catalysis/Electrocatalysis"}],"tags":[],"updatedAt":"2026-03-04T06:05:38+00:00","versionOfRecord":[],"versionCreatedAt":"2025-12-23 07:48:03","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-8346707","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-8346707","identity":"rs-8346707","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}