Hydrogen intercalation metal oxide cluster modified nickel electrode and preparation method and application thereof

Abstract

The invention belongs to the field of electrochemical materials, and particularly relates to a hydrogen intercalation metal oxide cluster modified nickel electrode and a preparation method and application thereof.The two faces of a nickel substrate are loaded with atomic-scale dispersed hydrogen intercalation metal oxide clusters, and the hydrogen intercalation metal oxide cluster modified nickel electrode is formed; wherein the hydrogen intercalation metal oxide cluster accounts for 0.8-2wt% of the total mass of the hydrogen intercalation metal oxide cluster modified nickel electrode; the hydrogen intercalation metal oxide comprises hydrogen intercalation molybdenum oxide, hydrogen intercalation tungsten oxide and hydrogen intercalation vanadium oxide. Compared with the prior art, the problem of poor UOR selectivity of an electrode material in an alkaline environment in the prior art is solved. According to the scheme, the hydrogen intercalation metal oxide is used for constructing a local subacid environment on the surface of the nickel base, and adsorption of OER reaction substrate hydroxyl on active nickel sites can be effectively repelled; and meanwhile, the UOR selectivity and the catalytic activity of the electrode material are synchronously improved by virtue of good hydrophilicity of the metal oxide.

Description

A hydrogen-intercalated metal oxide cluster-modified nickel electrode, its preparation method and application Technical Field

[0001] This invention belongs to the field of electrochemical materials, specifically relating to a hydrogen-intercalated metal oxide cluster modified nickel electrode, its preparation method, and its application. Background Technology

[0002] Electrochemical urea oxidation (UOR) is a key anodic half-reaction in environmental remediation and energy-related applications. This reaction converts urea in municipal and industrial wastewater into harmless nitrogen, providing a sustainable solution for denitrification of urea-containing wastewater. More importantly, because the thermodynamic potential of UOR (0.37 V vs. RHE) is significantly lower than that of the oxygen evolution reaction (1.23 V vs. RHE), coupling it with the cathodic hydrogen evolution reaction can significantly reduce the voltage input for hydrogen generation in urea-containing wastewater, making it a more energy-efficient alternative to traditional water splitting. However, the practical application of UOR still faces fierce competition from the oxygen evolution reaction (OER)—adverse OER side reactions can form explosive hydrogen-oxygen mixtures, leading to significant safety risks.

[0003] Inspired by the hydroxyl-bridged nickel active center in natural urease, nickel-based materials have become the most widely studied UOR electrocatalysts. Existing technologies, such as the ultrastable Ni nanoparticle reduction embedded in nickel molybdate nanorods (Ni-NiMoO4) disclosed in CN116497395A, effectively avoid catalyst aggregation during the catalytic process by reducing Ni nanoparticles onto NiMoO4 nanorods through the nanorod-nanoparticle structure. Another example is the bifunctional catalyst (MoO2-Ni / NF) disclosed in CN115896802A for electrochemical hydrogen evolution reaction and urea electrocatalytic oxidation reaction, which achieves hydrogen production from urea in alkaline solution by constructing Mo-O-Ni bonds and simultaneously containing divalent nickel and tetravalent molybdenum and / or hexavalent molybdenum. However, these existing technologies still have significant shortcomings for industrial applications. For example, regarding CN115896802A, although it exhibits certain UOR catalytic activity at low current densities, its performance at industrial-grade high current densities (>500 mA / cm²) is limited. 2 Under certain conditions, due to mass transfer limitations and kinetic matching issues of urea molecules, the UOR selectivity of this type of material decreases sharply. At this point, the electrode surface potential increases, significantly activating the thermodynamically more competitive OER, leading to intense competitive oxygen evolution at the anode. This not only reduces the Faraday efficiency of urea oxidation, making it ineffective in removing urea pollutants from wastewater; more critically, the large amount of oxygen generated at the anode can easily permeate through the diaphragm or be entrained by bubbles into the cathode products, potentially reaching the hydrogen-oxygen explosion limit under high-pressure conditions, posing a safety hazard.

[0004] Therefore, developing advanced catalyst engineering strategies based on active nickel substrates to ensure high selectivity of UOR relative to OER is of great significance for the development of energy-saving hydrogen production technology coupled with cathodes for electrochemical treatment of urea-containing wastewater. Summary of the Invention

[0005] The purpose of this invention is to address at least one of the aforementioned problems by providing a hydrogen-intercalated metal oxide cluster-modified nickel electrode, its preparation method, and its application, thereby resolving the issue of poor UOR selectivity in existing electrode materials under alkaline conditions. This solution utilizes hydrogen-intercalated metal oxides to construct a locally slightly acidic environment on the nickel-based surface, effectively repelling the adsorption of hydroxide ions (OER reaction substrates) at active nickel sites. Simultaneously, leveraging the excellent hydrogen affinity of metal oxides, it promotes the rapid dehydrogenation reaction of urea molecules through proton-coupled electron transfer, thereby simultaneously improving the UOR selectivity and catalytic activity of the electrode material.

[0006] The objective of this invention is achieved through the following technical solution: The first aspect of this invention discloses a hydrogen-intercalated metal oxide cluster modified nickel electrode, wherein atomically dispersed hydrogen-intercalated metal oxide clusters are loaded on both sides of a nickel substrate to form a hydrogen-intercalated metal oxide cluster modified nickel electrode; wherein the hydrogen-intercalated metal oxide clusters account for 0.8~2wt% of the total mass of the hydrogen-intercalated metal oxide cluster modified nickel electrode; the hydrogen-intercalated metal oxides include hydrogen-intercalated molybdenum oxide, hydrogen-intercalated tungsten oxide, and hydrogen-intercalated vanadium oxide.

[0007] Preferably, the nickel substrate comprises any one of nickel felt / nickel fiber, nickel foam, and nickel mesh; the area of ​​the nickel substrate is 0.25~400 cm². 2 .

[0008] The second aspect of the present invention discloses a method for preparing a hydrogen-intercalated metal oxide cluster modified nickel electrode as described above, comprising the following steps: acid washing pretreatment of a nickel substrate, immersing the pretreated nickel substrate in a solution containing a metal oxide precursor and ultrasonic treatment, drying and then calcining at high temperature in a reducing atmosphere to obtain the hydrogen-intercalated metal oxide cluster modified nickel electrode.

[0009] Preferably, the pretreatment method for pickling is as follows: immerse the nickel substrate in acid solution, ultrasonically treat for 5-30 minutes, then wash with water and ethanol 3-5 times in sequence, and then dry.

[0010] Preferably, the acid solution used in the pickling pretreatment is an aqueous solution of hydrogen chloride; wherein the concentration of hydrogen chloride is 0.1~1 mol / L.

[0011] Preferably, the metal oxide precursor is a chloride of a metal oxide; the metal oxide precursor is prepared into a solution containing the metal oxide precursor using ethanol as a dispersant; wherein the concentration of the metal in the solution containing the metal oxide precursor is 0.08~0.2 mol / L.

[0012] Preferably, the reducing atmosphere is a mixture of hydrogen and argon; wherein the partial pressure ratio of hydrogen to argon is 1:10~20.

[0013] Preferably, the conditions for high-temperature calcination are: a heating rate of 2~10℃ / min, a calcination temperature of 300~600℃, and a calcination time of 6~12 h.

[0014] The third aspect of this invention discloses the application of a hydrogen-intercalated metal oxide cluster-modified nickel electrode as described above in the urea oxidation reaction.

[0015] Preferably, the method is characterized by employing any one of the following: i) using a single electrolytic cell: the hydrogen-intercalated metal oxide cluster-modified nickel electrode is the working electrode, the mercury-mercury oxide electrode is the reference electrode, the platinum sheet electrode is the counter electrode, and the electrolyte solution is 0.1~1 mol / L potassium hydroxide and 0.05~0.5 mol / L urea; ii) using an anion exchange membrane electrolytic cell: the hydrogen-intercalated metal oxide cluster-modified nickel electrode is the anode, the Pt / C-loaded hydrophobic carbon cloth or monolithic nickel is the cathode, and the electrolyte solution is 0.1~1 mol / L potassium hydroxide and 0.05~0.5 mol / L urea; the flow rate of the anion exchange membrane electrolytic cell is 400~600 mL / min, and the operating temperature is 25~80℃.

[0016] The working principle of this invention is as follows: Defects are created on the nickel lattice surface through acid pretreatment, providing anchoring points for the metal oxide precursor. During drying and gradual heating, the metal oxide precursor hydrolyzes and dehydrates, condensing into amorphous molybdenum oxide. Simultaneously, nickel surface atoms interact with oxygen atoms in the molybdenum precursor, forming Ni-OX bridging oxygen bonds (X = Mo, W, V), stabilizing the metal species and limiting their migration and aggregation. At high temperature, nickel catalyzes the dissociation of hydrogen into atomic hydrogen, which embeds into the interlayer / lattice gaps of the metal oxide, forming hydrogen-intercalated metal oxide clusters.

[0017] By utilizing the hydrogen-intercalated metal oxide on the nickel substrate surface, a localized slightly acidic environment is formed, which repels the competitive adsorption of hydroxyl ions, the substrate for the OER reaction, on the metal site. With the help of the good hydrogen affinity of the metal oxide, the urea molecules are promoted to complete the dehydrogenation reaction rapidly through the proton-coupled electron transfer process, thereby simultaneously improving the UOR selectivity and activity of the electrode material.

[0018] Compared with the prior art, the present invention has the following beneficial effects: the present invention has excellent alkaline urea oxidation performance and selectivity, as well as excellent electrochemical stability at industrial current density. It is simple to prepare, low in cost, has good reproducibility, is easy to scale up, has the feasibility of large-scale production, has good commercial prospects, and helps to promote the industrial development of electrochemical treatment of urea-containing wastewater coupled with cathode energy-saving hydrogen production technology.

[0019] A catalyst with excellent UOR performance was prepared by modifying a nickel substrate with a non-noble transition metal oxide. The nickel substrate is characterized by easy scale-up production, environmental friendliness, low cost, and strong mechanical properties. Using nickel with a surface rich in lattice defects as a support, Ni-OX (X = Mo, W, V) chemical bonds are formed to ensure the strong bonding of metal clusters to the substrate surface. Utilizing the excellent hydrogenation catalytic properties of nickel, hydrogen molecules are promoted to dissociate into highly reactive atomic hydrogen on its surface, which then overflows to the adjacent molybdenum oxide species, embedding as protons into the interlayer or lattice gaps of molybdenum oxide, while simultaneously injecting electrons into the d orbitals of metal X.

[0020] The material prepared by this invention can be used directly as a working electrode without the need for binders and conductive agents, making it easy to scale up production and greatly simplifying the electrode preparation process. While ensuring UOR performance, the loading form of transition metal oxides is reduced to the nanoscale cluster scale, reducing the production cost of the electrode and laying the foundation for its large-scale preparation.

[0021] In the alkaline UOR reaction, the nickel electrode modified with hydrogen-intercalated metal oxide clusters achieves 1 A / cm 2 The potential under the current is only 1.45V RHE, exhibiting excellent intrinsic UOR activity; at an industrial-grade 1 A / cm 2 It can operate stably for over 3000 hours at current densities, demonstrating excellent stability; it can also operate stably at industrial-grade current densities of 1.5 A / cm². 2 At and below this range, the UOR selectivity can reach ~100%, and only nitrogen signal was detected in the gas products on the anode side, with no oxygen generation found. This indicates that the system can significantly suppress competitive OER and effectively avoid the explosion risk caused by the mixing of anode oxygen and cathode hydrogen. It can be directly applied to the treatment of actual urine-containing wastewater in anion exchange membrane electrolyzers and has ideal practical application prospects. Attached Figure Description

[0022] Figure 1 shows an aberration-corrected transmission electron microscope image of the nickel electrode modified with hydrogen-intercalated molybdenum oxide clusters prepared in Example 1.

[0023] Figure 2 shows the Raman spectrum of the hydrogen-intercalated molybdenum oxide cluster-modified nickel electrode prepared in Example 1.

[0024] Figure 3 shows the hydrogen-intercalated molybdenum oxide cluster-modified nickel electrode (H) prepared in Example 1. xMoO y Linear voltammetric curves of urea oxidation for the following nickel electrodes prepared: Mo1-Ni (Mo-Ni), Molybdenum single-atom modified nickel electrode prepared in Comparative Example 1, Nickel hydride electrode prepared in Comparative Example 2, Nickel electrode prepared in Comparative Example 3 (Ni), and MoO2-Ni (MoO2-Ni) prepared in Comparative Example 4.

[0025] Figure 4 shows the linear voltammetric curves of the hydrogen-intercalated molybdenum oxide cluster-modified nickel electrodes prepared in Example 1 and Comparative Example 1 in electrolytes with different urea concentrations.

[0026] Figure 5 shows the differential electrochemical mass spectra of the hydrogen-intercalated molybdenum oxide cluster-modified nickel electrodes prepared in Example 1 and Comparative Example 3.

[0027] Figure 6 shows the linear voltammetric curves of urea oxidation and water oxidation of the hydrogen-intercalated molybdenum oxide cluster-modified nickel electrode prepared in Example 1.

[0028] Figure 7 shows the performance of the hydrogen-intercalated molybdenum oxide cluster-modified nickel electrode prepared in Example 1 at 1 A / cm. 2 Electrochemical urea oxidation stability under [condition].

[0029] Figure 8 shows the linear voltammetric curves of urea oxidation for nickel electrodes with different hydrogen intercalation molybdenum oxide cluster loadings in Example 2.

[0030] Figure 9 shows the linear voltammetric curve of urea oxidation for the hydrogen-intercalated tungsten oxide / vanadium cluster-modified nickel electrode in Example 3.

[0031] Figure 10 shows the feedback cell voltage under different currents when the hydrogen-intercalated molybdenum oxide cluster-modified nickel electrode prepared in Example 4 is applied to an anion exchange membrane electrolyzer.

[0032] Figure 11 shows the stability of the hydrogen-intercalated molybdenum oxide cluster-modified nickel electrode prepared in Example 4 in an anion exchange membrane electrolyzer.

[0033] Figure 12 shows the degradation curve of urea pollutants in actual urine-containing wastewater treated by the hydrogen-intercalated molybdenum oxide cluster-modified nickel electrode prepared in Example 4. Detailed Implementation

[0034] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0035] Unless otherwise specified, the reagents used in the following description are conventional commercial products, the methods used are well-known in the art, and any other matters not covered herein may be handled using existing technology.

[0036] The purpose of this invention is to provide a hydrogen-intercalated molybdenum oxide / tungsten / vanadium cluster-modified nickel electrode and its preparation method, as well as the application of this electrode in the electrochemical urea oxidation reaction (UOR), to solve the problem of poor UOR selectivity of existing electrode materials under alkaline conditions. This invention utilizes hydrogen-intercalated molybdenum oxide / tungsten / vanadium to construct a locally slightly acidic environment on the nickel-based surface, which can effectively repel the adsorption of hydroxide ions, the substrate for the OER reaction, on the active nickel sites; simultaneously, by leveraging the good hydrogen affinity of molybdenum oxide / tungsten / vanadium, it promotes the rapid dehydrogenation reaction of urea molecules through proton-coupled electron transfer, thereby simultaneously improving the UOR selectivity and catalytic activity of the electrode material.

[0037] The objective of this invention is achieved through the following technical solutions (the following description uses molybdenum as an example, while tungsten and vanadium are in the same form and manner as molybdenum): In the first aspect, this invention discloses a hydrogen-intercalated molybdenum oxide cluster modified nickel electrode, wherein atomically dispersed hydrogen-intercalated molybdenum oxide clusters are loaded on both sides of a nickel substrate to form an integral electrode of hydrogen-intercalated molybdenum oxide cluster modified nickel.

[0038] Preferably, the molybdenum accounts for 0.8 to 2 wt% of the total mass of the nickel-based monolithic electrode.

[0039] Preferably, the nickel substrate comprises nickel felt / nickel fiber, nickel foam, and nickel mesh carrier, and the area of ​​the nickel substrate is 0.25~400 cm². 2 .

[0040] Secondly, the present invention discloses a method for preparing a nickel electrode modified by hydrogen intercalated molybdenum oxide clusters as described above. The method involves pre-treating a nickel substrate by acid washing, immersing the pre-treated nickel substrate in a solution containing a molybdenum precursor, performing ultrasonic treatment, drying, and then calcining at high temperature in a reducing atmosphere to obtain a nickel electrode modified by hydrogen intercalated molybdenum oxide clusters.

[0041] Preferably, in the pre-acid pickling step, the treatment method is to immerse the nickel substrate in an aqueous solution of hydrogen chloride, sonicate it for 5 to 30 minutes, then wash it with water and ethanol 3 to 5 times in sequence, and then dry it.

[0042] Preferably, in the pre-treatment of acid washing, the solution is an aqueous solution of hydrogen chloride with a concentration of 0.1~1 mol / L; more preferably, it is a 0.1 mol / L hydrogen chloride solution.

[0043] Preferably, in the precursor solution, the precursor of molybdenum is molybdenum chloride, and ethanol is used as a dispersant.

[0044] Preferably, the concentration of molybdenum in the precursor solution is 0.08~0.2 mol / L.

[0045] Preferably, the reducing atmosphere is a mixture of hydrogen and argon, with a partial pressure ratio of hydrogen to argon of 1:10~20.

[0046] Preferably, in the high-temperature calcination, the heating rate is 2~10℃ / min, the calcination temperature is 300~600℃, and the calcination time is 6~12 h.

[0047] Thirdly, this invention discloses the application of a nickel electrode modified with hydrogen-intercalated molybdenum oxide clusters as described above in the urea oxidation reaction.

[0048] Preferably, any one of the following methods is used: i) A single electrolytic cell is used: the hydrogen-intercalated molybdenum oxide cluster-modified nickel electrode is used as the working electrode, the mercury-mercury oxide electrode is used as the reference electrode, the platinum sheet electrode is used as the counter electrode, and the electrolyte solution is 0.1~1 mol / L potassium hydroxide and 0.05~0.5 mol / L urea; more preferably, it is a solution of 1 mol / L potassium hydroxide and 0.5 mol / L urea; ii) Anion exchange membrane electrolytic cell is used: the hydrogen-intercalated molybdenum oxide cluster-modified nickel electrode is used as the anode, the Pt / C-loaded hydrophobic carbon cloth is used as the cathode, the electrolyte solution is 0.1~1 mol / L potassium hydroxide and 0.05~0.5 mol / L urea, the flow rate is 400~600 mL / min, and the operating temperature is 25~80℃; more preferably, it is a solution of 1 mol / L potassium hydroxide and 0.5 mol / L urea, and the operating temperature is 45~65℃.

[0049] Example 1: Preparation method of hydrogen-intercalated molybdenum oxide cluster-modified nickel electrode, including the following steps: Nickel felt is cut into 1×0.5 cm pieces, ultrasonically treated with ethanol for 10 min to remove surface oil, and then ultrasonically treated in 0.1 mol / L dilute hydrochloric acid for 15 min. After pretreatment, the nickel felt is rinsed three times with water and ethanol respectively, and dried under an infrared lamp. 1 mL of 0.1 mol / L molybdenum chloride ethanol solution is prepared in a 1.5 mL centrifuge tube. The nickel felt is immersed in the above solution, ultrasonically treated for 10 min, and then dried under an infrared lamp. After complete drying, the nickel felt is placed in a corundum boat, then placed in a tube furnace. A 5% hydrogen / argon mixture is first passed through for 20 min, then the temperature is increased to 400℃ at a rate of 5℃ / min and held for 12 h. After returning to room temperature, it is rinsed with water and ethanol sequentially and dried to obtain the hydrogen-intercalated molybdenum oxide cluster-modified nickel electrode (H). x MoO y -Ni).

[0050] Characterization of the physical properties of the nickel electrode modified with hydrogen-intercalated molybdenum oxide clusters: The nickel electrode modified with hydrogen-intercalated molybdenum oxide clusters prepared in Example 1 was characterized by aberration-corrected transmission electron microscopy (TEM) and Raman spectroscopy. The AC-HAADF-STEM image in Figure 1 shows small clusters with a particle size of 1–2 nm distributed on the surface of the nickel substrate. The Raman spectrum in Figure 2 confirms that H…x MoO y Mo-O and Mo=O signals belonging to molybdenum oxide were detected on the Ni surface, as well as characteristic peaks of terminal / bridging Mo-OH formed after hydrogen intercalation into molybdenum oxide. These characterization results demonstrate that hydrogen-intercalated molybdenum oxide clusters were successfully loaded onto the nickel felt surface using the method of this invention.

[0051] Comparative Example 1: Nickel felt was cut into 1×0.5 cm pieces, ultrasonicated with water and ethanol for at least 15 min each, and dried under an infrared lamp. A 3 mg / mL molybdenum chloride ethanol solution was prepared, and 60 μL of the molybdenum chloride ethanol solution was evenly sprayed onto both sides of the nickel felt substrate and dried under an infrared lamp. After complete drying, the foamed nickel was placed in a corundum boat and then placed in a tube furnace. A hydrogen / argon mixture was first passed through for 30 min, and then the temperature was increased. The furnace was calcined at 400℃ for 3 h under a hydrogen / argon mixture atmosphere. After returning to room temperature, the furnace was rinsed with water and ethanol sequentially and dried to obtain a molybdenum single-atom modified nickel electrode (Mo1-Ni).

[0052] Comparative Example 2, based on Example 1, omits the molybdenum chloride ethanol solution to obtain a nickel hydride electrode (H-Ni).

[0053] Comparative Example 3, based on Example 1, only involved acid washing pretreatment of the nickel felt to obtain a nickel electrode (Ni).

[0054] Comparative Example 4: MoO2-Ni was prepared according to the technical solution proposed in patent CN115896802A. First, a 1×0.5 cm nickel felt was ultrasonically treated for 10 min in a mixture of 2 mol / L HCl and acetone / ethanol for 10 min. After removal, it was rinsed with deionized water and dried in a 60℃ oven for 12 h. 0.5 g of ammonium molybdate was dissolved in 30 mL of deionized water. After complete dissolution, it was transferred to a hydrothermal reactor, and the pretreated nickel felt was added. The reactor was hydrothermally heated at 120℃ for 6 h, allowed to cool naturally, and then rinsed with ethanol and water. The sample was placed in a quartz boat and then placed in a tube furnace. Nitrogen gas was first passed through for 20 min, and then the temperature was increased to 400℃ at a rate of 5℃ / min and held for 2 h to obtain a molybdenum dioxide-modified nickel electrode (MoO2-Ni).

[0055] Application and performance testing of hydrogen-intercalated molybdenum oxide cluster-modified nickel electrode in single-cell electrochemical urea oxidation reaction: A three-electrode system was constructed in a single cell using a CHI760E electrochemical workstation. The electrochemical performance (UOR) of the prepared electrode and its control group was tested. A platinum sheet electrode was used as the counter electrode, and a mercury-mercury oxide electrode was used as the reference electrode. The prepared material was directly used as the working electrode. The electrolyte was a 1 mol / L KOH solution and a 0.05~0.5 mol / L urea solution. The rotor speed was 800 rpm, and the temperature was 25℃. In this embodiment, the potentials of the polarization curves were converted to those of a reversible hydrogen electrode (RHE, E(RHE) = E(Hg / HgO) + 0.059 pH + 0.095 V).

[0056] In a nitrogen-saturated electrolyte, at 10 mV·s -1 A linear voltammetric curve was obtained by scanning at a certain scan rate.

[0057] As shown in Figure 3, in a solution of 1 mol / L KOH and 0.5 mol / L urea, H... x MoO y -Ni exhibits the best UOR performance, reaching 0.1 A·cm -2 0.5 A·cm -2 1 A·cm -2 The required potentials for the current densities of H1-Ni, H1-Ni, and Ni1-Ni are only 1.37 V, 1.41 V, and 1.45 V, respectively, which are much lower than the potentials required for Mo1-Ni, H1-Ni, Ni, and MoO2-Ni to achieve the same current densities. As shown in Figures 4 and 5, in 1 mol / L KOH and 0.05–0.33 mol / L urea solutions, H1-Ni... x MoO y -Ni both exhibited significantly better UOR catalytic activity than Ni. More importantly, H x MoO y The polarization curves of Ni-Ni exhibit a linear potential-current relationship, while the UOR current density of Mo1-Ni, H-Ni, Ni, and MoO2-Ni all show current passivation at high potentials (>1.50 V RHE). This is because the reaction process changes from a six-electron transfer UOR to a four-electron transfer OER, resulting in a decreasing current density with increasing potential. In-situ differential charge mass spectrometry results confirm that H... x MoO y Within the RHE potential range of 0.9 to 2.3 V, the signal intensity of nitrogen gas, the product of UOR (Ultra-Organic Reduction), showed a positive correlation with the increase or decrease of current density, while the signal of oxygen gas, the product of OER (Oxygen Reduction), was almost undetectable. In contrast, the nitrogen gas signal of the control group Ni was significantly weakened, and a distinct oxygen gas signal was observed. These results demonstrate that the H2O prepared by the technique of this invention...x MoO y -Ni can effectively suppress OER competition in the high potential range, exhibiting excellent UOR selectivity.

[0058] From a mechanism of action perspective, the hydrogenated molybdenum oxide clusters retain crystalline local structural features, with their framework primarily formed by Mo-O-Mo bonds, thus exhibiting hydrogen storage performance similar to that of hydrogen-molybdenum bronze. Specifically, the cluster interiors and interlayer voids can accommodate and stably anchor hydrogen atoms, where protons can bind to bridging oxygen sites, while electrons are injected into the d orbitals of molybdenum atoms, thereby achieving "hydrogen storage." The stored hydrogen species can construct a locally acidic microenvironment on the nickel substrate surface, where electrostatic attraction drives the preferential adsorption of negatively charged hydroxide ions at the electrode-electrolyte interface onto H₂O. x MoO y Cluster surface, thereby inhibiting OH - Direct adsorption at active nickel sites effectively avoids competitive oxygen exchange rate (OER). In contrast, molybdenum single atoms (Mo1-Ni) are dispersed in an isolated state on a nickel substrate, losing their hydrogen storage capacity due to the lack of lattice or interlayer structure; molybdenum dioxide-modified nickel (MoO2-Ni) is prepared by calcination under a nitrogen atmosphere, and its synthesis process does not involve a hydrogen storage step. Therefore, neither of these catalysts can construct the aforementioned slightly acidic environment on the electrode surface. Consequently, both Mo1-Ni and MoO2-Ni catalysts struggle to achieve excellent UOR selectivity at high current densities.

[0059] As shown in Figure 6, compared with OER, H x MoO y -Ni reaches 1.05 A·cm at UOR. -2 The potential required for the current density was reduced by 0.27 V, resulting in a reduction of approximately 16.7% in hydrogen production energy consumption. Further findings revealed that H... x MoO y -Ni at industrial-grade current density 1 Acm -2 It can operate continuously for more than 3,000 hours (Figure 7), demonstrating its superior electrochemical stability.

[0060] The above results demonstrate that the nickel electrode modified with hydrogen-intercalated molybdenum oxide clusters exhibits excellent activity, selectivity, and stability in the electrochemical oxidation of urea, and has high potential for practical applications.

[0061] Example 2 describes a method for preparing nickel electrodes with different hydrogen-intercalated molybdenum oxide cluster loadings, comprising the following steps: Based on Example 1 (0.1 mol / L), the concentration of the molybdenum chloride solution is varied. The nickel felt is ultrasonically dissolved in a 0.06 mol / L molybdenum chloride ethanol solution to obtain H… x MoO yA nickel electrode with a hydrogen-intercalated molybdenum oxide cluster loading of 0.3% was prepared; the nickel felt was ultrasonically dissolved in a 0.2 mol / L molybdenum chloride ethanol solution to obtain H... x MoO y A nickel electrode with a 2% hydrogen-intercalated molybdenum oxide cluster loading. (Adding H...) x MoO y The loading amount can gradually increase the UOR activity of the electrode, but as shown in Figure 8, when the loading amount is increased from 1% to 2%, the UOR performance is not significantly improved.

[0062] Example 3 describes a method for preparing other hydrogen-intercalated oxide cluster-modified nickel electrodes, comprising the following steps: Based on Example 1, the precursor solution is changed to an ethanol solution of tungsten chloride and vanadium chloride. Nickel is ultrasonically dissolved in a 0.1 mol / L tungsten chloride ethanol solution to obtain a hydrogen-intercalated tungsten oxide cluster-modified nickel electrode; nickel is then ultrasonically dissolved in a 0.1 mol / L vanadium chloride ethanol solution to obtain a hydrogen-intercalated vanadium oxide cluster-modified nickel electrode. As shown in Figure 9, the polarization curves of the above hydrogen-intercalated oxide cluster-modified nickel electrodes all exhibit a linear potential-current relationship, indicating excellent UOR selectivity; and compared to the OER process, this electrode can achieve a potential reduction, thereby achieving energy-saving hydrogen production.

[0063] Example 4: Preparation method of hydrogen-intercalated molybdenum oxide cluster-modified nickel electrode, including the following steps: Nickel foam is processed into 2×2 cm pieces, surface oil is removed by ultrasonication with ethanol for 10 min, and then ultrasonicated in 0.1 mol / L dilute hydrochloric acid for 15 min. After pretreatment, the nickel felt is rinsed three times with water and three times with ethanol, and then dried under an infrared lamp. 8 mL of 0.1 mol / L molybdenum chloride ethanol solution is prepared in a beaker, and the nickel felt is immersed in the solution, ultrasonicated for 10 min, and then dried under an infrared lamp. After complete drying, the nickel felt is placed in a tube furnace, and a hydrogen / argon mixture is passed through for 20 min, then the temperature is increased. Calcination is carried out at 400℃ for 12 h under a hydrogen / argon mixed atmosphere. After returning to room temperature, the electrode is rinsed with water and ethanol sequentially and then dried to obtain the hydrogen-intercalated molybdenum oxide cluster-modified nickel electrode (H…). x MoO y -Ni).

[0064] Application and performance testing of hydrogen-intercalated molybdenum oxide cluster-modified nickel in anion exchange membrane electrolyzer: An anion exchange membrane electrolyzer was used. The hydrogen-intercalated molybdenum oxide cluster-modified nickel electrode prepared in Example 4 was used as the anode, and the cathode was a hydrophobic carbon cloth loaded with Pt / C. The anion exchange membrane was PiperION-A80-HCO3, the electrolyte solution was 1 mol / L potassium hydroxide and 0.5 mol / L urea solution, the flow rate was 550 mL / min, and the operating temperature was 25~80℃. As shown in Figure 10, with the increase of the cell pressure, the performance of the nickel electrode loaded with H... x MoO y The AEMWE current density of -Ni increases rapidly, significantly higher than that of Ni-based electrolyzers, and exhibits a good linear relationship between cell voltage and current density. This indicates that H x MoO y -Ni exhibits excellent UOR activity and selectivity in anion exchange membrane electrolyzers, effectively avoiding the explosion risk caused by the mixing of anolyte oxygen byproducts permeating the membrane with hydrogen. Figure 11 further confirms that this device can operate at an industrial-grade current density of 1 A / cm². 2 It can operate stably for over 250 hours, demonstrating excellent stability. Furthermore, after replacing the electrolyte with a mixed solution of actual urine wastewater and 1 mol / L potassium hydroxide, H... x MoO y -Ni can achieve complete removal of urea pollutants in 20 cycles (Figure 12), demonstrating excellent electrochemical stability and recyclability potential, and has application prospects in the industrialization of electrolysis of urea-containing wastewater coupled with energy-saving hydrogen production.

[0065] This invention anchors hydrogen-intercalated molybdenum oxide onto the surface of a nickel substrate to prepare an anode material with high UOR selectivity, activity, and stability. The loading of the hydrogen-intercalated molybdenum oxide is adjustable, and the molybdenum oxide can be replaced with tungsten oxide and vanadium oxide. The material exhibits superior electrochemical stability, uses inexpensive raw materials, and employs a simple process, which is beneficial for the scale-up production and practical industrial applications of the electrode. The hydrogen-intercalated molybdenum oxide can construct a locally slightly acidic environment near the active nickel sites, inhibiting the adsorption of hydroxide ions, the OER reaction substrate, on nickel. Simultaneously, leveraging the good hydrogen affinity of molybdenum oxide, it promotes the rapid dehydrogenation reaction of urea molecules through proton-coupled electron transfer, greatly improving the UOR selectivity and catalytic activity of the electrode material.

[0066] In summary, this invention presents a hydrogen-intercalated metal oxide cluster-modified nickel electrode, formed by loading atomically dispersed hydrogen-intercalated molybdenum / tungsten / vanadium oxide clusters onto both sides of a nickel substrate. Compared to existing nickel-based electrocatalytic materials, this invention solves the problem of poor selectivity in the electrochemical urea oxidation reaction (UOR) of traditional materials. Traditional techniques use nickel-based catalysts to catalyze the UOR process, but in alkaline environments, they are susceptible to intense competition from the oxygen evolution reaction (OER), resulting in the mixing of generated oxygen with hydrogen produced at the cathode, posing an explosion hazard. This invention utilizes hydrogen-intercalated molybdenum / tungsten / vanadium oxides to construct a locally slightly acidic environment on the nickel-based surface, effectively repelling the adsorption of hydroxyl ions, the OER reaction substrate, on active nickel sites. Simultaneously, leveraging the good hydrogen affinity of molybdenum / tungsten / vanadium oxides, it promotes the rapid dehydrogenation reaction of urea molecules through proton-coupled electron transfer, thereby simultaneously improving the UOR selectivity and catalytic activity of the electrode material.

[0067] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A nickel electrode modified with hydrogen-intercalated metal oxide clusters, characterized in that, Atomic-scale dispersed hydrogen-intercalated metal oxide clusters are loaded on both sides of a nickel substrate to form a hydrogen-intercalated metal oxide cluster-modified nickel electrode; wherein the hydrogen-intercalated metal oxide clusters account for 0.8~2wt% of the total mass of the hydrogen-intercalated metal oxide cluster-modified nickel electrode; the hydrogen-intercalated metal oxides include hydrogen-intercalated molybdenum oxide, hydrogen-intercalated tungsten oxide and hydrogen-intercalated vanadium oxide.

2. The nickel electrode modified with hydrogen-intercalated metal oxide clusters according to claim 1, characterized in that, The nickel substrate includes any one of nickel felt / nickel fiber, nickel foam, and nickel mesh; the area of ​​the nickel substrate is 0.25~400 cm². 2 .

3. A method for preparing a nickel electrode modified with hydrogen intercalated metal oxide clusters as described in claim 1 or 2, characterized in that, The process includes the following steps: pre-treatment of the nickel substrate by acid washing, immersing the pre-treated nickel substrate in a solution containing a metal oxide precursor and ultrasonic treatment, drying and then calcining at high temperature in a reducing atmosphere to obtain the hydrogen intercalated metal oxide cluster modified nickel electrode.

4. The method for preparing a hydrogen-intercalated metal oxide cluster-modified nickel electrode according to claim 3, characterized in that, The pickling pretreatment method is as follows: the nickel substrate is immersed in acid solution, ultrasonically treated for 5 to 30 minutes, then washed with water and ethanol 3 to 5 times in sequence, and then dried.

5. The method for preparing a hydrogen-intercalated metal oxide cluster-modified nickel electrode according to claim 3, characterized in that, The acid solution used in the pickling pretreatment is an aqueous solution of hydrogen chloride; wherein the concentration of hydrogen chloride is 0.1~1 mol / L.

6. The method for preparing a hydrogen-intercalated metal oxide cluster-modified nickel electrode according to claim 3, characterized in that, The metal oxide precursor is a chloride of a metal oxide; the metal oxide precursor is prepared into a solution containing the metal oxide precursor using ethanol as a dispersant; wherein the concentration of the metal in the solution containing the metal oxide precursor is 0.08~0.2 mol / L.

7. The method for preparing a hydrogen-intercalated metal oxide cluster-modified nickel electrode according to claim 3, characterized in that, The reducing atmosphere is a mixture of hydrogen and argon; wherein the partial pressure ratio of hydrogen to argon is 1:10~20.

8. The method for preparing a hydrogen-intercalated metal oxide cluster-modified nickel electrode according to claim 3, characterized in that, The conditions for high-temperature calcination are as follows: heating rate of 2~10℃ / min, calcination temperature of 300~600℃, and calcination time of 6~12 h.

9. The application of a hydrogen-intercalated metal oxide cluster-modified nickel electrode as described in claim 1 or 2 in the urea oxidation reaction.

10. The application according to claim 9, characterized in that, The following methods can be used: i) Using a single electrolytic cell: the hydrogen-intercalated metal oxide cluster-modified nickel electrode is used as the working electrode, the mercury-mercury oxide electrode is used as the reference electrode, the platinum sheet electrode is used as the counter electrode, and the electrolyte solution is 0.1~1 mol / L potassium hydroxide and 0.05~0.5 mol / L urea; ii) Using an anion exchange membrane electrolytic cell: the hydrogen-intercalated metal oxide cluster-modified nickel electrode is used as the anode, the Pt / C-loaded hydrophobic carbon cloth or monolithic nickel is used as the cathode, and the electrolyte solution is 0.1~1 mol / L potassium hydroxide and 0.05~0.5 mol / L urea; the flow rate of the anion exchange membrane electrolytic cell is 400~600 mL / min, and the operating temperature is 25~80℃.

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