A biomimetic proton-transfer microenvironment copper-based nanozyme catalyst, its preparation method, and its application in the electrocatalytic reduction of nitrate to ammonia.

Abstract

This invention discloses a biomimetic proton-transferring microenvironment copper-based nanozyme catalyst, its preparation method, and its application in the electrocatalytic reduction of nitrate to ammonia, relating to the field of electrochemical wastewater treatment and resource recovery technology. This invention focuses on nitrate pollutants commonly found in wastewater, addressing the bottleneck problems of low treatment efficiency and potential threats to the ecological environment posed by traditional processes. It utilizes electrochemical hydrogen intercalation to construct Cu-H... x The MoO3 / NF biomimetic catalytic system simulates the proton transfer microenvironment in CuNIRs to achieve bulk H + Pre-storage and relay supply provide a novel low-energy, high-selectivity strategy for NO3RR. Achieving FE (efflux rate) of 98% or higher at a relatively low overpotential of -0.35 V vs. RHE (hydrothermal activity) effectively suppresses HER. Maintaining high NH3 yield over a wide pH range of 3–13 demonstrates good potential for practical applications.

Description

Technical Field

[0001] This invention relates to the field of electrochemical wastewater treatment and resource recovery technology, and in particular to a biomimetic proton transfer microenvironment copper-based nanoenzyme catalyst, its preparation method, and its application in the electrocatalytic reduction of nitrate to ammonia. Background Technology

[0002] Nitrate (NO3-) pollution in water bodies mainly originates from agricultural, industrial, and domestic wastewater. Excessive discharge can lead to eutrophication and may convert into carcinogens such as nitrite (NO2-), threatening the ecosystem and human health. Meanwhile, ammonia (NH3) is both an important chemical raw material and a potential clean energy carrier. Traditional Haber-Bosch ammonia synthesis processes are energy-intensive and produce large carbon emissions, while electrocatalytic nitrate reduction to ammonia (NO3RR) technology can directly convert pollutants into ammonia, turning waste into treasure and offering both environmental and economic benefits.

[0003] However, existing NO3RR technologies still face many challenges in practical applications. First, the reduction of nitrate to ammonia involves a multi-step proton-electron coupling transfer process, resulting in a complex reaction pathway and slow kinetics. Second, the reaction is prone to competitive hydrogen evolution reaction (HER), leading to poor ammonia selectivity and low Faraday efficiency. Furthermore, the accumulation of the intermediate product NO2- not only reduces ammonia yield but may also cause secondary pollution. Although copper-based catalysts exhibit good activity in the initial NO3- activation stage, subsequent NO2- hydrogenation steps often suffer from adverse effects due to active hydrogen species (H+). Limited supply or inefficient utilization hinders efficient end-to-end conversion. Furthermore, the hydrogen supply path relies on water dissociation to generate H₂. This process requires high potentials and is prone to HER, severely limiting the Faraday efficiency (FE). Notably, in natural copper nitrite reductases (CuNIRs), the Cu active site is not isolated but surrounded by histidine (His) and aspartic acid (Asp) residues. These residues interact via hydrogen bonds to construct a dynamic proton (H+) transport network, rapidly and directionally transferring captured H+ to the active site, enabling efficient reduction under mild conditions. Therefore, mimicking the H+ transport microenvironment within the enzyme cavity to construct a catalytic system that directly utilizes pre-intercalated H+ holds promise for achieving efficient and highly selective NO3RR at lower potentials. Summary of the Invention

[0004] The purpose of this invention is to provide a biomimetic proton transfer microenvironment copper-based nanozyme catalyst, its preparation method, and its application in the electrocatalytic reduction of nitrate to ammonia, thereby addressing the following shortcomings in existing NO3RR technology: reliance on water dissociation to generate H+. As a hydrogen source, it requires a high overpotential and consumes a lot of energy, and is prone to initiating competitive HER, resulting in generally low FE levels; although copper-based catalysts can effectively activate NO3... - However, in the subsequent NO2 - Due to insufficient supply and utilization of active hydrogen species in the hydrogenation step, the conversion efficiency is limited, and the intermediate product NO2 is produced. - It is prone to accumulation; lacks rational design of proton transport pathways, has slow reaction kinetics, a narrow efficient operating potential window, and is difficult to operate stably in a wide pH range and complex wastewater environments. The biomimetic proton transport microenvironment copper-based nanozyme catalyst of this invention can reduce the overpotential required for NO3RR, inhibit HER side reactions, and improve the FE and yield of NH3; it solves the problems of insufficient hydrogen supply and NO2 in traditional copper-based catalysts. - Accumulated problems, achieving NO3 - This invention provides a highly efficient NO3RR catalytic system that can operate stably over a wide pH range and under real wastewater conditions, achieving efficient conversion to NH3 throughout the entire process.

[0005] To achieve the above objectives, the present invention provides the following solution: One of the technical solutions of the present invention: a method for preparing a copper-based nanozyme catalyst for a biomimetic proton transfer microenvironment, comprising the following steps: A Mo source, polyvinylpyrrolidone (PVP, used as a structure-directing agent, stabilizer, dispersant, and reducing agent), a substrate, and water were mixed and heated to react. The product of the heated reaction was then placed in a Cu... 2+ The product was immersed in solution and then heat-treated to obtain Cu-MoO3 / substrate. Using the Cu-MoO3 / substrate as the working electrode, Cu-H was obtained by cyclic voltammetry. x MoO3 / substrate is the copper-based nanozyme catalyst for the biomimetic proton transport microenvironment.

[0006] This invention uses the proton transport microenvironment in natural CuNIRs as a biomimetic prototype to construct Cu-H single-atom doped hydrogen-molybdenum bronze (Cu-H) through an electrochemical hydrogen intercalation strategy. x MoO3 catalytic system; utilizing the high theoretical proton capacity of MoO3, H+ is formed through electrochemical hydrogen intercalation. x MoO3 phase was used to construct a three-dimensional hydrogen bond network, simulating the proton transfer channels in the enzyme cavity to achieve bulk H + Pre-storage and relay supply; Cu is doped in H in single-atom form (mainly +1 valence). x In the MoO3 lattice, a Cu-O-Mo bridging structure is formed, simulating the T2Cu active center in CuNIRs; rapid proton conduction is achieved through the Grotthuss proton hopping mechanism, enabling H... +It migrates from stable sites within the bulk phase to active Cu sites at the interface at low energy barriers, directly participating in multi-step proton-coupled electron transfer processes, thus avoiding water dissociation at high potentials to produce H+. The path.

[0007] Furthermore, the Mo source includes (NH4)6Mo7O 24 ·4H2O.

[0008] Further, the substrate includes nickel foam (NF). When the substrate is NF, the resulting Cu-MoO3 / substrate specifically forms a Cu-MoO3 / NF electrode, and the resulting Cu-H x MoO3 / substrate is specifically Cu-H x MoO3 / NF electrode (i.e., biomimetic proton transfer microenvironment copper-based nanozyme catalyst electrode).

[0009] Furthermore, the ratio of the Mo source, polyvinylpyrrolidone, and water is 1.236 g:0.2 g:10-30 mL.

[0010] Furthermore, the heating reaction is carried out at a temperature of 100 °C for a duration of 12-18 h.

[0011] Furthermore, after the heating reaction is completed, the product of the heating reaction is dried at 60 °C for 10-14 h, and then subjected to Cu... 2+ The steps of soaking in the solution.

[0012] Furthermore, the Cu 2+ The solution is an anhydrous ethanol solution of CuCl2·2H2O with a concentration of 4 mg / mL. -1 The soaking time is 1-3 hours.

[0013] Furthermore, the heat treatment temperature is 400 °C and the time is 1-3 h.

[0014] Furthermore, prior to the heat treatment, the product after soaking is dried at 60 °C for 10-14 h.

[0015] Furthermore, using the Cu-MoO3 / substrate as the working electrode, Cu-H was obtained by cyclic voltammetry. x The MoO3 / substrate step includes: cyclic voltammetry of the Cu-MoO3 / substrate in a 0.5 M H2SO4 electrolyte at potentials ranging from -0.25 V vs. RHE to 0.1 V vs. RHE at 50 mV s⁻¹. -1 The scanning rate is repeated 20-200 times.

[0016] Furthermore, a pretreatment step of the substrate is included before mixing the Mo source, polyvinylpyrrolidone, substrate, and water.

[0017] The second technical solution of the present invention: a biomimetic proton transfer microenvironment copper-based nanozyme catalyst prepared according to the above preparation method.

[0018] Furthermore, the Cu-H x The x value in the MoO3 / substrate is 0.1-0.9.

[0019] The third technical solution of the present invention: the application of the above-mentioned biomimetic proton transfer microenvironment copper-based nanozyme catalyst in the electrocatalytic reduction of nitrate to ammonia.

[0020] The present invention discloses the following technical effects: This invention focuses on nitrate pollutants commonly found in wastewater. Addressing the bottleneck issues of low treatment efficiency and potential threats to the ecological environment posed by traditional processes, it constructs Cu-H through electrochemical hydrogen intercalation. x The MoO3 / NF biomimetic catalytic system simulates the proton transfer microenvironment in CuNIRs to achieve bulk H + Pre-storage and relay supply provide a novel low-energy, high-selectivity strategy for NO3RR. Achieving FE (efflux rate) of 98% or higher at a relatively low overpotential of -0.35 V vs. RHE (hydrothermal activity) effectively suppresses HER. Maintaining high NH3 yields over a wide pH range of 3–13 demonstrates good potential for practical applications. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 MoO3 / NF, Cu-MoO3 / NF and Cu-H x XRD pattern of MoO3 / NF.

[0023] Figure 2 Cu-H x HRTEM characterization results of MoO3 / NF, where a is Cu-H x TEM image of MoO3 / NF, bd represents Cu-H. x EDS elemental distribution diagram of MoO3 / NF (b represents Mo, c represents Cu, and d represents O).

[0024] Figure 3For H x MoO3 / NF, Cu-MoO3 / NF and Cu-H x XPS plots of MoO3 / NF, where a represents Cu-MoO3 / NF and Cu-H x Cu 2p spectrum of MoO3 / NF, b represents H. x MoO3 / NF, Cu-MoO3 / NF and Cu-H x Mo 3d spectrum of MoO3 / NF, c is H x MoO3 / NF, Cu-MoO3 / NF and Cu-H x O 1s spectrum of MoO3 / NF.

[0025] Figure 4 Cu-H x NEXAFS spectra of MoO3 / NF (a), EXAFS spectra of Fourier transform (b), Cu-H in R space (c) and K space (d) x EXAFS fitting of MoO3 / NF and EXAFS spectrum of wavelet transform (e).

[0026] Figure 5 For H x MoO3 / NF, Cu-MoO3 / NF and Cu-H x MoO3 / NF NO3 at different potentials - -N removal rate (a), NH3 yield (b), FE for NH3 production (c), and selectivity (d).

[0027] Figure 6 For H x MoO3 / NF, Cu-MoO3 / NF and Cu-H x ESR signal of MoO3 / NF in 0.05 M Na2SO4 electrolyte at -0.35 V vs. RHE potential.

[0028] Figure 7 Cu-H x Linearized pseudo-first-order kinetic curves of MoO3 / NF at different TBA concentrations.

[0029] Figure 8 Cu-H x EIS spectra of MoO3 / NF (a) and Cu−MoO3 / NF (b) at different temperatures (inset: equivalent circuit); Cu-H x Proton conductivity (c) and activation energy (d) of MoO3 / NF and Cu−MoO3 / NF at different temperatures.

[0030] Figure 9 Cu-Hx Optimized hydrogen adsorption structures at different sites on MoO3 / NF (a), Cu-H x Hydrogen binding energy barrier on MoO3 / NF (b), Cu-H x Optimized hydrogen adsorption configurations (c) at different sites on MoO3 / NF, Cu-H x Hydrogen transfer barrier (d) on MoO3 / NF.

[0031] Figure 10 Cu-H x NH3 yields of MoO3 / NF and Cu-MoO3 / NF at different pH values. Detailed Implementation

[0032] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0033] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0034] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0035] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0036] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0037] It should be noted that any aspects not described in detail in this invention are conventional practices in the field and are not the focus of this invention.

[0038] In the following embodiments, comparative examples and test examples of the present invention, if room temperature is involved, it specifically refers to 20~30 ℃.

[0039] All raw materials used in the following embodiments, comparative examples and test examples of this invention are common commercially available products. Among them, the size of the nickel foam is 2 cm × 4 cm × 1 mm, and the PVP is specifically PVPK30.

[0040] Example 1 A biomimetic proton transport microenvironment copper-based nanozyme catalyst, the preparation steps of which are as follows: (1) The nickel foam (NF) was first sonicated in 10wt% HCl solution for 5 min, then sonicated in anhydrous ethanol for 5 min, and then dried to obtain the pretreated NF.

[0041] (2) 1.236 g (NH4)6Mo7O 24 A mixture of 4H₂O, 0.2 g PVP, and pretreated NF was transferred to a 100 mL reactor containing 30 mL of water and heated at 100 °C for 18 h. The resulting product was dried at 60 °C for 12 h. Subsequently, the product was processed in 5 mL of a 4 mg / mL solution. -1 The product was soaked in anhydrous ethanol solution of CuCl2·2H2O for 2 h and then dried at 60 °C for 12 h. The resulting product was heated at 400 °C for 2 h to obtain the product Cu-MoO3 / NF.

[0042] (3) Cu-H was synthesized using Cu-MoO3 / NF as the working electrode via cyclic voltammetry (CV) in a standard three-electrode cell system (with Ag / AgCl as the reference electrode and Pt as the counter electrode) using a CHI 760E electrochemical workstation. x MoO3 / NF material. Specifically, the obtained Cu-MoO3 / NF electrode was subjected to CV in a 0.5 M H2SO4 electrolyte at a potential range of -0.25 V vs. RHE to 0.1 V vs. RHE at 50 mV s. -1 The scan rate was repeated 200 times to form Cu-H. x MoO3 / NF electrode material is a copper-based nanozyme catalyst for a biomimetic proton transfer microenvironment.

[0043] Comparative Example 1 The preparation of MoO3 / NF is as follows: (1) Preprocess the NF, and the preprocessing steps are the same as in Example 1 to obtain the preprocessed NF.

[0044] (2) 1.236 g (NH4)6Mo7O 24 A mixture of 4H₂O, 0.2 g PVP, and pretreated NF was transferred to a 100 mL reactor containing 30 mL of water and heated at 100 °C for 18 h. The resulting product was dried at 60 °C for 12 h. Subsequently, the product was heated at 400 °C for 2 h to obtain the product MoO₃ / NF.

[0045] Comparative Example 2 H x The preparation of MoO3 / NF is as follows: Using MoO3 / NF prepared in Comparative Example 1 as the working electrode, H was synthesized in a standard three-electrode cell system via cyclic voltammetry (CV) using a CHI 760E electrochemical workstation. x MoO3 / NF material. Specifically, the MoO3 / NF electrode was subjected to CV in a 0.5 M H2SO4 electrolyte at a potential range of -0.25 V vs. RHE to 0.1 V vs. RHE at 50 mV s. -1 The scan rate is repeated 200 times to form H x MoO3 / NF electrode material.

[0046] Test Example 1 This test example uses a variety of characterization techniques to characterize the samples prepared in Example 1 and Comparative Examples 1-2.

[0047] first, Figure 1 MoO3 / NF, Cu-MoO3 / NF and Cu-H x X-ray diffraction (XRD) patterns of MoO3 / NF were analyzed to determine Cu-H content. x The crystal structure of MoO3 / NF electrode material, its main diffraction peaks and H 0.9 The presence of the MoO3 phase (PDF#53-1024) confirms that hydrogen has been successfully embedded in the MoO3 lattice, forming a hydrogen-molybdenum bronze phase. Furthermore, no metallic Cu, CuO, or Cu2O phases were detected, indicating that Cu is dispersed in the material at the atomic scale.

[0048] In addition, this test example uses high-resolution transmission electron microscopy (HRTEM) to examine Cu-H x The local lattice structure of the MoO3 / NF sample was analyzed, and the results are as follows: Figure 2 As shown, where a is Cu-H x TEM image of MoO3 / NF, bd represents Cu-H. xEDS elemental distribution map of MoO3 / NF (b represents Mo, c represents Cu, d represents O). TEM images show different lattice features. Measurements show that the lattice fringe spacing corresponding to the clear region in the TEM image is 0.336 nm, which is similar to that of hydrogen-molybdenum bronze H. 0.9 The (202) crystal plane of MoO3 is consistent with the standard value, confirming the formation of a new phase after hydrogen intercalation. Furthermore, some regions exhibit lattice fringes that are deformed, blurred, or even disordered, primarily due to the large amount of H₂ produced during electrochemical hydrogenation. + The embedding of these elements induces lattice strain and surface defects. EDS elemental distribution maps show that Mo, Cu, and O are present in Cu-H₂O. x The MoO3 / NF samples exhibit a highly consistent and uniform spatial distribution.

[0049] Furthermore, this test example uses X-ray photoelectron spectroscopy (XPS) to study H. x MoO3 / NF, Cu-MoO3 / NF and Cu-H x The elemental valence states and chemical environment of the MoO3 / NF surface were systematically analyzed, and the results are as follows: Figure 3 As shown, where a represents Cu-MoO3 / NF and Cu-H x Cu 2p spectrum of MoO3 / NF, b represents H. x MoO3 / NF, Cu-MoO3 / NF and Cu-H x Mo 3d spectrum of MoO3 / NF, c is H x MoO3 / NF, Cu-MoO3 / NF and Cu-H x The O 1s spectrum of MoO3 / NF. (See attached image.) Figure 3 As shown in Figure a, a double peak can be observed in the Cu 2p spectrum, where Cu... + The significant increase in the relative intensity of the characteristic peaks indicates that low-valence Cu (Cu) + The proportion of α-Cu increased significantly and it became the dominant valence state. Notably, this dominant low-valence Cu species closely matches the oxidation state of T2Cu, a key catalytic active site in CuNIRs. The T2Cu site can effectively stabilize the reaction intermediate bridging NO2. - Therefore, Cu-H x Cu enriched on the MoO3 / NF surface + Species hold promise as potentially highly efficient catalytic sites for NO3RR. Furthermore, in Cu-H... x In the MoO3 / NF sample, Mo 4+ The proportion of the component further increased. A large amount of Mo... 5+ and Mo 4+The stable presence of the species in the electrochemical hydrogen intercalation material strongly confirms the formation of a highly protonated hydrogen-molybdenum bronze structure during the intercalation process. Figure 3 (b) For example Figure 3 As shown in Figure c, in addition to the existing O1 and O2 peaks, a new peak (O3) appears at a higher binding energy of 533.6 eV in the O 1s spectrum. The appearance of this O3 peak is usually associated with surface hydroxyl groups or oxygen species in adsorbed water molecules. Meanwhile, the O2 peak at 532.5 eV shows an intensity at H... x MoO3 / NF and Cu-H x A significant enhancement was also observed in both MoO3 / NF samples. This trend is mainly attributed to H. + Embedding leads to a large number of H + The formation of bonded terminal oxygen, and the increase in its content, are directly reflected in the significant increase in the intensity of the O2 peak, further confirming the formation of the hydrogen-molybdenum bronze structure and the deepening of the surface protonation.

[0050] Furthermore, in order to investigate the prepared Cu-H x The chemical state and local coordination environment of Cu in MoO3 / NF materials were investigated in this test example, and Cu K-edge X-ray absorption fine structure (XAFS) measurements were performed. Figure 4 a shows Cu-H x Normalized Cu K-edge X-ray absorption near-edge structure (NEXAFS) spectra of MoO3 / NF samples and reference materials (Cu foil, Cu2O, and CuO). The figures show that Cu-H... x The absorption edge position and near-edge characteristics of MoO3 / NF are similar to those of Cu. + The results show a high degree of agreement with the standard Cu₂O. This indicates that the doped Cu species mainly exist in the +1 valence state, consistent with the XPS analysis results. To further resolve the local atomic structure of Cu atoms, Fourier transform (FT) was performed on the EXAFS spectrum. The EXAFS spectrum after Fourier transform is shown below. Figure 4 As shown in b, Cu-H x The FT-EXAFS spectrum of MoO3 / NF shows a main peak at R≈1.47 Å, which can be attributed to the Cu-O scattering pathway of the first coordination shell. Notably, no characteristic peak corresponding to Cu-Cu metallic bonds was observed near R≈2.30 Å, ruling out the formation of Cu clusters or metallic Cu nanoparticles, thus confirming that Cu species are present in H... x MoO3 exists as isolated single atoms. To more intuitively distinguish the contributions of different backscattered atoms, wavelet transform (WT) was used to analyze the EXAFS signal. The wavelet transform EXAFS spectrum (i.e., WT spectrum) is shown below. Figure 4As shown in Figure e. The WT spectrum provides resolution in both k-space and R-space. For Cu-H x A maximum intensity was observed at R≈3.60 Å in MoO3 / NF, corresponding to Cu-O coordination. A shoulder peak appeared at R≈2.16 Å, consistent with the theoretical expectation of the Cu-Mo scattering path. This result directly confirms the existence of a Cu-O-Mo bridging structure in the sample, i.e., Cu atoms are connected to neighboring Mo atoms through O atoms. Furthermore, to quantitatively obtain the coordination parameters, EXAFS data were fitted, and Cu-H coordination parameters were obtained in both R-space and K-space. x The EXAFS fittings of MoO3 / NF are as follows: Figure 4 c and Figure 4 As shown in Figure d, the structural parameters obtained from the fitting are summarized in Table 1. The results show that the Cu-O coordination number is approximately 4.01, with a bond length of 1.95 Å. The Cu-O-Mo coordination number is approximately 1.08, with a bond length of 3.22 Å. These quantitative results further confirm that Cu atoms substitute for H atoms. x Mo sites in the MoO3 lattice coordinate with adjacent Mo sites through oxygen bridges, thereby constructing an isolated Cu-O-Mo interface structure.

[0051] Table 1. Cu-H₂O obtained from EXAFS analysis x Structural parameters of the MoO3 / NF sample Test Example 2 NO3RR Performance Test: To systematically investigate the NO3RR performance of various catalyst samples, this test example used a three-electrode H-type electrolytic cell as the reactor. Within the potential range of -0.3 V vs. RHE to -0.6 V vs. RHE, the performance of each catalyst sample (H...) was measured. x MoO3 / NF electrode, Cu-MoO3 / NF electrode or Cu-H x MoO3 / NF electrode was used as the electrochemical cathode (working electrode), Ag / AgCl as the reference electrode, and Pt electrode as the counter electrode. 500 mg L -1 NO3 - A mixed solution of -N+50 mM Na2SO4 was used as the cathode electrolyte, and a 50 mM Na2SO4 solution was used as the anolyte for potentiostatic measurements. Ultraviolet-visible spectrophotometry was used to analyze the reactants and the main nitrogen-containing product (NO3). - -N, NO2 - -N and NH4 + The concentration of -N was quantitatively analyzed, and the FE and corresponding yield of each catalyst at different potentials were calculated accordingly. The results are as follows: Figure 5 As shown. Figure 5 For H x MoO3 / NF, Cu-MoO3 / NF and Cu-H x MoO3 / NF NO3 at different potentials - -N removal rate (a), NH3 yield (b), FE for NH3 production (c), and selectivity (d). It can be seen that at -0.35V vs. RHE, Cu-H... x MoO3 / NF exhibited a high FE of 98%, while its NH3 yield reached 77.7 mmol h⁻¹. −1 g cat −1 The selectivity for NH3 reached 89.3%, and for NO3... - -N removal rate reached 91.3%, achieving the optimal synergy between high selectivity and high activity.

[0052] Furthermore, to further elucidate the existence forms of active hydrogen species in NO3RR and their behavior at the electrochemical interface, this test example employed ESR spectroscopy, combined with the spin trapping agent 5,5-dimethyl-1-pyrrolline-N-oxide (DMPO), to systematically analyze the evolution of hydrogen species in each catalyst sample under reaction conditions. The results are as follows: Figure 6 As shown. Figure 6 For H x MoO3 / NF, Cu-MoO3 / NF and Cu-H x The ESR signal of MoO3 / NF in 0.05 M Na2SO4 electrolyte at -0.35 V vs. RHE potential shows that Cu-H x No characteristic ESR signal belonging to the DMPO-H adduct was detected in MoO3 / NF under these conditions. This phenomenon indicates that on the surface of materials with hydrogen intercalation structures, the active species released during electrochemical reduction are not in the form of H. It resides at the electrode interface for a long time in the form of H, and tends to remain in the form of H. + The hydrogen intercalation structure participates in subsequent electrochemical reaction steps in the form of hydrogen. This result is highly consistent with the hydrogen intercalation characteristics of the material, confirming that the hydrogen intercalation structure can act as a hydrogen intercalation mechanism. + The medium or reservoir for transmission regulates the reaction pathway through PCET (proton-coupled electron transfer).

[0053] To further demonstrate the differences in the forms of active hydrogen species revealed by the above ESR analysis, tert-butanol (TBA) was selected as the H2O species in this test example. The quencher was investigated, and its effect on the NO3RR reaction kinetics on the electrode material was systematically examined. The results are as follows: Figure 7 As shown, Figure 7 Cu-H xThe linearized pseudo-first-order kinetic curves of MoO3 / NF at different TBA concentrations show that... x On the MoO3 / NF electrode, when the TBA concentration increases from 0 to 100 mM, the pseudo-first-order reaction rate constant of the NO3RR reaction ( k obs From 0.52542 h −1 Slightly decreased to 0.41796 h −1 This finite rate decay indicates that H It is not the key active species driving the NO3RR process on this electrode. This result further confirms the presence of hydrogen intercalation structures in Cu-H... x In MoO3 / NF materials, H⁺ is mainly transported rapidly through the bulk phase or interface to participate in the reaction, rather than H⁺. The form accumulates on the surface and acts as the main reducing agent.

[0054] Electrochemical impedance spectroscopy (EIS) is an effective tool for studying electrode process kinetics and ion transport behavior. Therefore, this test example further employed EIS technology to test the electrode material in the temperature range of 298 K to 323 K to reveal its H₂ content. + Differences in conduction dynamics and their underlying mechanisms, results as follows Figure 8 As shown. Figure 8 Cu-H x EIS spectra of MoO3 / NF (a) and Cu−MoO3 / NF (b) at different temperatures (inset: equivalent circuit); Cu-H x The proton conductivity (c) and activation energy (d) of MoO3 / NF and Cu−MoO3 / NF at different temperatures were measured using EIS spectra. The EIS spectra showed a clear temperature dependence; at all test temperatures, Cu−H… x The bulk impedance of MoO3 / NF was significantly lower than that of Cu-MoO3 / NF, indicating that the former has a faster Ht. + Bulk transport rate. Further calculations yielded Cu-MoO3 / NF and Cu-H... x The proton conductivity of MoO3 / NF at 25 °C is 7.71 × 10⁻⁶. -6 S cm −1 and 2.32×10 -4 S cm −1 As temperature increases, the proton conductivity of both materials shows an increasing trend, and Cu-H... x The proton conductivity of MoO3 / NF is higher than that of Cu-MoO3 / NF at all test temperatures. To reveal the proton conduction mechanism, the proton migration activation energy of the two materials was calculated. For Cu-H xThe activation energy of MoO3 / NF is only 0.11 eV, which indicates that H + The migration primarily occurs through the Grotthussian proton transport mechanism (proton hopping), which relies on a three-dimensional hydrogen bond network formed by intercalated hydrogen species, via H... + The synergistic process of structural reorganization and hydrogen bond breaking / formation enables rapid non-diffusional conduction.

[0055] To gain a deeper understanding of H at the atomic scale + In Cu-H x The embedding site preference and subsequent migration behavior in MoO3 / NF were analyzed in this test case using density functional theory (DFT) to calculate the hydrogen binding energy (E) within the system. H A systematic analysis was conducted on the hydrogen transfer energy barrier (ΔG). For example... Figure 9 As shown in a and b, a is Cu-H x Optimized hydrogen adsorption structures at different sites on MoO3 / NF, b is Cu-H x The hydrogen binding energy barrier on MoO3 / NF shows that sites 1 and 2 are located near the Cu single atom lattice positions, and their E H The values ​​were -1.43 and -1.93 eV, respectively, indicating that the hydrogen binding energy at these two sites was weak, and the adsorbed hydrogen was easily desorbed and participated in the subsequent NO3RR process. In contrast, sites 3, 4, and 5, located inside the material, showed stronger hydrogen adsorption capacity, E H The values ​​were -4.19, -4.54, and -4.66 eV, respectively, especially the E at site 5. H The most negative value indicates that it is thermodynamically most favorable to H. + Stable adsorption of H. This calculation result reasonably explains the stable adsorption of H during the electrochemical hydrogen intercalation process. + The phenomenon of preferentially selecting site 5 for embedding within the lattice is observed. Based on this, this test case further evaluates H... + The kinetic probability of migration from internal stable sites to reactive interfaces was calculated using H. + The migration path from site 5 to site 1. For example... Figure 9 As shown in c and d, c is Cu-H x Optimized hydrogen adsorption configurations at different sites on MoO3 / NF, where d represents Cu-H. x The hydrogen transfer barrier on MoO3 / NF shows that the calculated value of the migration barrier gradually decreases, indicating that H⁺ has a low migration barrier from site 5 to site 1. This strongly supports the evidence that H⁺ in Cu−H x MoO3 / NF can achieve rapid, low-resistance migration within the bulk phase.

[0056] To further verify the actual impact of the aforementioned proton transport mechanism on the reaction pathway, this test case investigated the effect of electrolyte pH on electrode catalytic activity. Specifically, the NH3 yield of the electrode was tested within a pH range of 3–13 (using a three-electrode H-type electrolytic cell as the reactor, at -0.35 V vs. RHE, with each catalyst sample as the electrochemical cathode, Ag / AgCl as the reference electrode, and Pt as the counter electrode, 500 mg L… -1 NO3 - A mixed solution of -N+50 mM Na2SO4 was used as the cathode electrolyte, and a 50 mM Na2SO4 solution was used as the anolyte for potentiostatic testing. The pH values ​​of the cathode and anolytes were controlled to be the same (3-13) by adding acid-base adjusters. The results are as follows: Figure 10 As shown. Figure 10 Cu-H x The NH3 yields of MoO3 / NF and Cu-MoO3 / NF at different pH values ​​show that Cu-H x The NH3 yield of MoO3 / NF remained high across the entire pH range with minimal fluctuations. This phenomenon is closely related to its hydrogen intercalation structure, meaning that a large number of H atoms are pre-embedded within the material's crystal lattice. + It can be directly used as a hydrogen source in the NO3RR process, thus affecting the H in the electrolyte. + It has a weak concentration dependence.

[0057] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for preparing a copper-based nanozyme catalyst for a biomimetic proton transport microenvironment, characterized in that, Includes the following steps: Mo source, polyvinylpyrrolidone, substrate, and water were mixed and heated to react. The product of the heated reaction was then placed in Cu. 2+ The product was immersed in solution and then heat-treated to obtain Cu-MoO3 / substrate. Using the Cu-MoO3 / substrate as the working electrode, Cu-H was obtained by cyclic voltammetry. x MoO3 / substrate is the copper-based nanozyme catalyst of the biomimetic proton transport microenvironment.

2. The preparation method of the biomimetic proton transfer microenvironment copper-based nanozyme catalyst as described in claim 1, characterized in that, The Mo source includes (NH4)6Mo7O 24 ·4H2O.

3. The preparation method of the biomimetic proton transfer microenvironment copper-based nanozyme catalyst as described in claim 1, characterized in that, The substrate includes nickel foam.

4. The preparation method of the biomimetic proton transfer microenvironment copper-based nanozyme catalyst as described in claim 1, characterized in that, The ratio of the Mo source, polyvinylpyrrolidone, and water is 1.236 g: 0.2 g: 10-30 mL.

5. The preparation method of the biomimetic proton transport microenvironment copper-based nanozyme catalyst as described in claim 1, characterized in that, The heating reaction is carried out at a temperature of 100 °C for 12-18 h.

6. The preparation method of the biomimetic proton transfer microenvironment copper-based nanozyme catalyst as described in claim 1, characterized in that, The Cu 2+ The solution is an anhydrous ethanol solution of CuCl2·2H2O with a concentration of 4 mg / mL. -1 The soaking time is 1-3 hours.

7. The preparation method of the biomimetic proton transport microenvironment copper-based nanozyme catalyst as described in claim 1, characterized in that, The heat treatment is performed at a temperature of 400 °C for 1-3 h.

8. The preparation method of the biomimetic proton transfer microenvironment copper-based nanozyme catalyst as described in claim 1, characterized in that, Using the Cu-MoO3 / substrate as the working electrode, Cu-H was obtained by cyclic voltammetry. x The MoO3 / substrate step includes: cyclic voltammetry of the Cu-MoO3 / substrate in a 0.5 M H2SO4 electrolyte at potentials ranging from -0.25 V vs. RHE to 0.1 V vs. RHE at 50 mV s⁻¹. -1 The scanning rate is repeated 20-200 times.

9. A biomimetic proton transfer microenvironment copper-based nanozyme catalyst prepared by the preparation method according to any one of claims 1-8.

10. The application of a copper-based nanozyme catalyst with a biomimetic proton transfer microenvironment as described in claim 9 in the electrocatalytic reduction of nitrate to ammonia.

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