Composite nanostructure catalyst and its application for hydrogen production from seawater by small molecule electro-oxidation assisted electrolysis

Abstract

This invention belongs to the field of electrochemical catalysis, specifically relating to a composite nanostructure catalyst and its application in small-molecule electrooxidation-assisted seawater electrolysis for hydrogen production. This application constructs a unique NiCo2Se4 composite nanostructure catalyst modified with vanadium oxide and containing oxygen vacancies and Lewis acid sites, which can be used in small-molecule electrooxidation reactions such as urea oxidation (UOR), methanol oxidation (MOR), and 5-hydroxymethylfurfural oxidation (HMFOR) in seawater environments. It also reveals for the first time the presence of oxygen vacancies (O... v The induced lattice oxygen mechanism (LOM) significantly promotes the formation of N-O bonds, thereby greatly accelerating the formation of NO2 from UOR. ⁻ Based on the reaction kinetics, NiCo2Se4@VO ultimately requires only 1.24 V and 1.40 V relative to a reversible hydrogen electrode (RHE) to achieve 100 and 1000 mA cm⁻¹, respectively. ‑2 It exhibited excellent NO2 ⁻ With selectivity (Faraday efficiency up to 92.77%), it exhibits excellent UOR catalytic performance and long-term service stability.

Description

Technical Field

[0001] This invention belongs to the field of electrochemical catalysis, specifically relating to a composite nanostructure catalyst and its application in small molecule electro-oxidation-assisted seawater electrolysis for hydrogen production. Background Technology

[0002] Seawater electrolysis for hydrogen production is an important way to resolve the contradiction between freshwater resource shortages and hydrogen energy development. However, traditional seawater electrolysis faces two major bottlenecks: first, the kinetics of the oxygen evolution reaction (OER) at the anolyte are slow, requiring a high overpotential; second, chloride ions in seawater cause electrode corrosion and competitive chloride oxidation reaction (ClOR), reducing efficiency and catalyst stability. Replacing OER with electro-oxidation reactions of smaller molecules such as alcohols, aldehydes, and urea, which are thermodynamically more advantageous, is considered a promising solution. Their theoretical oxidation potentials are significantly lower than those of traditional OER (theoretical potential 1.23 V vs. RHE). Furthermore, these reactions not only facilitate efficient seawater decomposition for hydrogen release but also enable the simultaneous electrosynthesis of high-value-added products. Typical examples include the electro-oxidation of methanol (MOR), 5-hydroxymethylfurfural (HMFOR), and urea (UOR), which have been widely applied in this field, producing formic acid (HCOO). ⁻ ), 2,5-furandicarboxylic acid (FDCA) and nitrite (NO2) ⁻ High-value-added chemicals such as [list of chemicals]. However, their practical application still faces challenges due to the difficulty in precisely controlling the reaction pathway and the high overpotential caused by the multi-electron transfer process.

[0003] Taking urea electro-oxidation (UOR) as an example, its theoretical voltage is only 0.37 V vs. RHE. However, traditional UOR processes often follow intramolecular N-N coupling pathways, mainly generating low-value products such as N2, CO2, and H2O, which limits their economic viability. Furthermore, because the reaction involves a slow 6-electron / 6-proton transfer process, it typically requires a high overpotential to drive it, especially at industrial-grade current densities. In an alkaline environment, when the NO bond formation rate exceeds the N-N coupling kinetics, the urea molecule will undergo multiple hydroxyl (OH) reactions. ⁻ Attack-induced dehydrogenation and oxygenation, thereby generating NO. x Species (NO2) ⁻ Or NO3 ⁻ This environmentally friendly electrosynthesis strategy avoids the traditional high-energy-consuming NOx synthesis method. x The production process (Ostwald process) involves environmental impacts from the emission of harmful gases. Therefore, by regulating the catalyst to promote NO bond formation and inhibit the N-N coupling pathway, it is hoped that efficient urea oxidation and simultaneous electrosynthesis of high-value nitrogen-containing compounds can be achieved, providing a new pathway for the synergistic development of clean energy conversion and green chemical production.

[0004] Currently, researchers induce Lewis acid-base effects by modifying or altering Lewis acid sites in catalysts, thereby enriching Lewis bases (OH-) in electrochemical reactions. ⁻ This allows for precise control of the reaction pathway of specific reactions (such as OER, glycerol oxidation, etc.). In fact, this advantageous local OH... ⁻ Enrichment can accelerate the kinetics of the excessive oxidation pathway of urea and inhibit intramolecular NN coupling, which is expected to open up new avenues for the preparation of higher value-added products through UOR.

[0005] However, the complex multi-electron transfer process severely limits the conversion of urea into nitrogen oxides (NOx). x The efficiency of nitrogen oxides (NOx) is a challenge. To address this issue, researchers have employed various methods to improve UOR kinetics, such as elemental doping, interface engineering, and the use of single-atom catalysts. x The conversion efficiency of these catalysts is not high (Faraday efficiency is often <85%), and their stability also needs to be improved. Therefore, there is an urgent need to develop new catalyst optimization strategies or catalytic mechanisms to significantly improve the electro-oxidation efficiency (Faraday efficiency >90%) and stability of urea and other small molecules under seawater conditions, so as to meet the practical needs of large-scale seawater electrolysis. Summary of the Invention

[0006] The purpose of this invention is to provide a composite nanostructure catalyst.

[0007] Another object of the present invention is to provide the application of the above-mentioned composite nanostructure catalyst.

[0008] Another object of the present invention is to provide applications of the above-mentioned composite nanostructure catalysts for promoting the production of nitrite from UOR, formic acid from MOR, and 2,5-furandicarboxylic acid from HMFOR.

[0009] The composite nanostructure catalyst according to the present invention is prepared by a method comprising the following steps: The nickel foam was soaked in acetone and dilute hydrochloric acid in sequence, washed and dried to obtain pretreated nickel foam. Precursor preparation: Pretreated nickel foam was placed in a mixed solution of Co(NO3)2·6H2O, Ni(NO3)2·6H2O and urea, and subjected to hydrothermal reaction at 100~120℃ for 10 hours in an autoclave. After cooling, the reacted nickel foam was removed, washed and dried to obtain NiCo-LDH precursor.

[0010] Electrodeposition: A mixed solution of 2 mmol NaVO3, NaNbO3, or NaTaO3 with 2–4 mmol oxalic acid was used as the electrolyte. A three-electrode system was employed for potentiostatic deposition to load the corresponding metal-oxalate complexes onto the surface of the prepared NiCo-LDH precursor. The specific steps are as follows: Potentialiostatic deposition was performed using an electrochemical workstation at a working voltage of -0.8 to -1.2 V vs. RHE. The working electrode was the NiCo-LDH precursor, the counter electrode was a graphite rod, and the reference electrode was an Ag / AgCl electrode. After deposition, the resulting sample was repeatedly rinsed with distilled water several times and dried overnight at 60°C.

[0011] Selenization treatment: Selenium powder is placed in the upstream zone of a dual-temperature zone tube furnace, and the electrodeposited NiCo-LDH precursor is placed in the downstream zone. Under argon protection, the selenium source zone is heated to 500℃ and the sample zone is heated to 300~500℃. The temperature is maintained for 2 hours and then naturally cooled to room temperature to obtain the corresponding composite electrode materials NiCo2Se4@VO, NiCo2Se4@NbO or NiCo2Se4@TaO.

[0012] According to the technical solution of this application, by adjusting the metal / oxalic acid feed ratio (metal:oxalic acid = 1:1~1:2) during the electrodeposition process, NiCo2Se4@XO (X is V, Nb or Ta) composite electrode materials with different oxygen vacancy concentrations can be obtained after selenization treatment.

[0013] According to the technical solution of this application, the optimal vanadium / oxalic acid feed ratio is 1:1.5, and the optimal Lewis acid layer is VO.

[0014] This invention also provides the application of the composite nanostructure catalyst prepared above in catalyzing small molecule electro-oxidation reactions, including but not limited to: UOR, MOR, and HMFOR.

[0015] The present invention has the following beneficial effects: (1) This application constructs a unique system with oxygen vacancies (O v A NiCo2Se4 composite nanostructure catalyst modified with vanadium oxide and Lewis acid sites (NiCo2Se4@VO) can be used for UOR, MOR, and HMFOR in seawater environments. Taking UOR as an example, V in NiCo2Se4@VO, acting as a Lewis acid site, can effectively enrich OH groups. ⁻ This guides the UOR path towards NO⁻ generation, rather than N₂. Furthermore, the enriched OH... ⁻ The composition of Cl ⁻ The repulsion layer ensures the stability of the catalyst. More importantly, it reveals for the first time the O vStructure-induced LOM promotes NO bond formation, thereby significantly reducing UOR generation of NO2. ⁻ Based on the reaction kinetics, NiCo2Se4@VO ultimately requires only 1.24 V and 1.40 V relative to RHE to reach 100 and 1000 mA cm⁻¹, respectively. -2 And it demonstrated excellent NO2. ⁻ Selectivity was high, with a Faraday efficiency of 92.77 ± 4.29% (1.35 V vs. RHE) and a yield of 236.8 ± 4.07 mg h. -1 cm -2 (1.40 V vs. RHE), and can achieve a stable UOR process for 1000 hours (10 constant voltage tests, each lasting 100 hours). It demonstrates good UOR catalytic performance and stability.

[0016] (2) This application constructs a device based on NiCo2Se4@VO anode for UOR nitrite production and enhanced seawater electrolysis hydrogen production, requiring only 1.81 V to achieve 1 A cm⁻¹. -2 It boasts industrial-grade current density and over 1200 hours of long-term stability, with hydrogen production energy consumption as low as 3.72 kWh / m³. -3 H2 .

[0017] (3) The NiCo2Se4@VO anode can be extended to the electro-oxidation of methanol (MOR) and 5-hydroxymethylfurfural (HMFOR) in seawater, and can efficiently prepare HCOO respectively. ⁻ (FE was 92.41%) and FDCA (FE was 88.55%). Attached Figure Description

[0018] Figure 1 The images show the morphology and structure of the NiCo2Se4@VO catalyst, including scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images. Figure 2 This shows that O in the NiCo2Se4@VO catalyst v Characterization, including aberration-corrected scanning transmission electron microscopy images, O 1s XPS spectra, EPR spectra, O v Content quantification comparison chart; Figure 3 The graphs show the UOR performance and stability of the catalyst in seawater electrolysis, including LSV curve comparison, product Faradaic efficiency distribution at different potentials, long-term cycle stability test, and surface OH content. ⁻ and Cl ⁻ Distributed TOF-SIMS images; Figure 4The diagram shows the overall seawater electrolysis system, a comparison of the long-term stability of the HER||UOR and HER||OER systems, and physical photos and XRD patterns of the anode products. Figure 5 Spectroscopic evidence for the study of reaction mechanism includes EPR spectrum of DMPO-*OH, relationship between UOR current density and KOH concentration, comparison of UOR product selectivity under different KOH concentrations, and in-situ FTIR spectrum; Figure 6 Key experiments demonstrating the role of oxygen vacancies and LOM include a comparison of LSV curves and Tafel slopes in the presence of TMAH inhibitors, and O 18 Time-sequential in-situ Raman spectroscopy and isotope-labeled mass spectrometry analysis of labeled catalysts; Figure 7 This diagram serves as a validation of the universality of LOM in various small molecule electro-oxidation reactions, including schematic diagrams of AEM and LOM pathways, comparison of LSV curves in OER, MOR, and HMFOR reactions, comparison of overpotential increments caused by TMAH inhibitors, and comparison of the contributions of LOM to various small molecule electro-oxidation reactions, including overpotential contribution, production efficiency contribution, and reaction kinetic effects. Detailed Implementation

[0019] To enable those skilled in the art to better understand the present invention, a detailed description is provided below in conjunction with the accompanying drawings and embodiments, but this is not intended to limit the scope of protection of the present invention.

[0020] According to specific embodiments of this application, the composite nanostructure catalyst of the present invention is prepared by a method comprising the following steps: The nickel foam was soaked in acetone and dilute hydrochloric acid in sequence, washed and dried to obtain pretreated nickel foam. Precursor preparation: Pretreated nickel foam was placed in a mixed solution of Co(NO3)2·6H2O, Ni(NO3)2·6H2O and urea, and hydrothermal reaction was carried out in an autoclave at 100~120℃ for 10 hours. After cooling, the reacted nickel foam was taken out, washed and dried to obtain NiCo-LDH precursor. Electrodeposition: A mixed solution of 2 mmol NaVO3, NaNbO3, or NaTaO3 with 2–4 mmol oxalic acid was used as the electrolyte. A three-electrode system was employed for potentiostatic deposition to load the corresponding metal-oxalate complexes onto the surface of the prepared NiCo-LDH precursor. The specific steps are as follows: Potentialiostatic deposition was performed using an electrochemical workstation at a working voltage of -0.8 to -1.2 V vs. RHE. The working electrode was the NiCo-LDH precursor, the counter electrode was a graphite rod, and the reference electrode was an Ag / AgCl electrode. After deposition, the resulting sample was repeatedly rinsed with distilled water several times and dried overnight at 60°C.

[0021] Selenization treatment: Selenium powder is placed in the upstream zone of a dual-temperature zone tube furnace, and the NiCo-LDH bulk is placed in the downstream zone. Under argon protection, the selenium source zone is heated to 500℃, and the sample zone is heated to 300~500℃. The temperature is maintained for 2 hours, and then naturally cooled to room temperature to obtain a NiCo2Se4 needle-shaped array electrode. If the sample after electrodeposition is used as the target for selenization treatment, corresponding composite electrode materials (NiCo2Se4@VO, NiCo2Se4@NbO, or NiCo2Se4@TaO) can be obtained.

[0022] Preferably, the catalyst is a vanadium oxide-coated nickel-cobalt selenide nanoneedle array with the chemical formula NiCo2Se4@VO, and the catalyst surface is rich in Lewis acid sites and O. v The catalyst has a heterogeneous structure, with a spinel-structured NiCo2Se4 core and a VO layer as the outer shell; the Lewis acid type of the catalyst can be controlled by electrodepositing different types of metal salts, O v The concentration can be controlled by adjusting the ratio of vanadium source to oxalic acid during the synthesis process.

[0023] Based on different NaVO3 to oxalic acid feed ratios, different O3- content was synthesized. v Concentration of catalyst (NiCo2Se4@VO) 1:2 NiCo2Se4@VO 1:1.5 and NiCo2Se4@VO 1:1 ), to explore O v The effect of concentration on UOR activity, in order to screen for the optimal O v Concentration catalyst.

[0024] According to specific embodiments of this application, in the electrodeposition step, catalysts with different Lewis acid layers (NiCo2Se4@NbO and NiCo2Se4@TaO) are synthesized using complexes of two other metals (niobium and tantalum) from group VB and oxalic acid.

[0025] The catalyst prepared using the above-described method is applied to the electrolysis of urea-containing seawater. The reaction is carried out in an H-type cell, with the electrocatalytic material serving as the working electrode, a graphite rod as the counter electrode, and an Hg / HgO electrode as the reference electrode. The anolyte is alkaline seawater and urea, and the catholyte is alkaline seawater, thus performing UOR-assisted seawater decomposition.

[0026] The mechanism of nitrite electrosynthesis using UOR is as follows: OH groups in the solution are enriched through the Lewis acid-base effect induced by the V sites in NiCo2Se4@VO. ⁻ This guides the UOR reaction towards more OH groups. ⁻ NO2 demand ⁻The pathway proceeds. Furthermore, the enriched OH... ⁻ A negatively charged layer is formed on the electrode surface, repelling corrosive Cl-. ⁻ This improves stability. More importantly, the abundant O in the VO Lewis acid layer... v It can activate LOM, allowing the adsorbed *OH to react directly with the catalyst lattice oxygen, avoiding the adsorption-desorption energy barrier limitation of intermediates in the traditional AEM process, and significantly accelerating UOR kinetics. The NiCo2Se4@VO composite catalyst can be used to catalyze other small molecule electro-oxidation reactions, including MOR and HMFOR.

[0027] Therefore, in a specific embodiment of this application, the apparatus for enhancing seawater electrolysis hydrogen production using NiCo2Se4@VO anode for UOR nitrite production utilizes NiCo2Se4@VO as the anode material and Ni2P / Co(PO3)2 as the cathode. The electrolyte is alkaline seawater containing 0.5 M urea and 1 M KOH. The apparatus also includes a flow reaction tank, an electrochemical workstation, a peristaltic pump, and an electrolyte storage tank. The reaction tank includes a cathode reaction tank and an anode reaction tank, separated by an anion exchange membrane and connected to the electrolyte storage tank via the peristaltic pump. During the reaction, the peristaltic pump fills the cathode and anode of the flow reaction tank. A constant voltage experiment is conducted at the electrochemical workstation, with the voltage set to 1.81 V vs. RHE. After a period of time, the product in the anode storage tank is collected.

[0028] The anode product is purified by steps including alcohol extraction of the anode electrolyte, freeze crystallization, and high-temperature purification to obtain solid nitrite product.

[0029] The NiCo2Se4@VO catalyst provided by this invention exhibits excellent UOR catalytic performance, requiring only 1.24 V and 1.40 V relative to RHE to achieve 100 and 1000 mA cm⁻¹, respectively. -2 And it demonstrated excellent NO2. ⁻ Selectivity was high, with a Faraday efficiency of 92.77 ± 4.29% (1.35 V vs. RHE) and a yield of 236.8 ± 4.07 mg h. -1 cm -2 (1.40 V vs. RHE), and can achieve a stable UOR process for 1000 hours (10 constant voltage tests, each lasting 100 hours). It demonstrates good UOR catalytic performance and stability. Example 1: Preparation of NiCo2Se4@VO, NiCo2Se4@NbO, and NiCo2Se4@TaO catalysts

[0030] (1) Pretreatment of nickel foam: First, a piece of nickel foam (1.5cm × 2.0cm) was cleaned sequentially with hydrochloric acid solution, acetone, and deionized water. Then, the cleaned NF was heated to 60°C. ° Dry in a vacuum environment at temperature C for later use.

[0031] (2) Preparation of NiCo-LDH precursor: Co(NO3)2·6H2O, Ni(NO3)2·6H2O and urea were dissolved in deionized water (40 mL) and sonicated for 30 minutes to obtain a mixed solution. This solution and pretreated nickel foam (1.5 cm × 2.0 cm) were sealed in a polytetrafluoroethylene-lined autoclave and heated at 100~120 °C. ° A hydrothermal reaction was carried out at C for 10 hours. After cooling, the final product was removed, ultrasonically cleaned with deionized water and ethanol, and then subjected to a 60°C reaction. ° Vacuum drying at C for 12 hours.

[0032] (3) Electrodeposition: A three-electrode system was used to perform potentiostatic deposition using a mixture of 2 mmol NaVO3, NaNbO3, or NaTaO3 with 2–4 mmol oxalic acid as the electrolyte. The working electrode was NiCo-LDH; the counter electrode was a graphite rod; and the reference electrode was Ag / AgCl. Corresponding metal-oxalate complexes were loaded onto the surface of the prepared NiCo-LDH precursor. The specific steps were as follows: Potentialiostatic deposition was performed using an electrochemical workstation at a working voltage of -0.8 to -1.2 V vs. RHE. After 450 seconds of deposition, the working electrode was flipped and the process was repeated. After deposition, the resulting sample was rinsed several times with distilled water and dried overnight at 60°C.

[0033] (4) Selenization treatment: Selenium powder is placed in the upstream zone of a dual-temperature zone tube furnace, and the precursor NiCo-LDH or the precursor NiCo-LDH after electrodeposition is placed in the downstream zone. Under argon protection, the selenium source zone is heated to 500°C and the sample zone is heated to 300~500°C. The temperature is maintained for 2 hours and then naturally cooled to room temperature to obtain NiCo2Se4 needle array electrode and the corresponding composite electrode materials NiCo2Se4@VO, NiCo2Se4@NbO, and NiCo2Se4@TaO. Example 2: Characterization of catalyst structure and components

[0034] like Figure 1 As shown, SEM and TEM indicate that the NiCo2Se4@VO catalyst maintains the morphology of the nanoneedle array. Figure 2 (Figures a and b in the text). HRTEM ( Figure 1Figures c and d in the image show a clear core-shell heterostructure, with the (111) crystal plane of the inner NiCo2Se4 layer coexisting with the (200) crystal plane of the outer VO layer. Aberration-corrected STEM revealed the presence of O in the VO layer. v ( Figure 2 Figures a and b in the image). XPS O1s spectrum ( Figure 2 Figure c in the diagram) and EPR spectrum ( Figure 2 The d-plot and e-plot in the figure quantitatively show that O in NiCo2Se4@VO v The concentration is 3.2 times that of pure NiCo2Se4. Example 3: UOR performance test of catalyst in seawater

[0035] The test was conducted in alkaline seawater containing 0.5 M urea and 1 M KOH. (For example...) Figure 3 As shown in Figures a and b, NiCo2Se4@VO only requires 1.40 V vs. RHE to reach 1 A cm⁻¹. -2 The performance was significantly better than the control group (NiCo2Se4@NbO / NiCo2Se4@TaO and NiCo2Se4, as well as comparative catalysts with different oxygen vacancy concentrations). For example... Figure 3 As shown in Figure c, at 1.35V, it affects the NO2 content of NiCo2Se4@VO. ⁻ The Faraday efficiency reaches 92.77%. Furthermore, the overpotential of the NiCo2Se4@VO driven UOR is 0.41 V lower than that of the OER, highlighting its energy-saving advantage. Figure 3 (Figure d). Figure 3 The e-graph shows that at 1 A cm -2 After 1000 hours of cycling testing, performance degradation was minimal, which can be attributed to the catalyst's effect on OH. ⁻ The enrichment of Cl ⁻ The repulsion layer ensures the stability of the catalyst. Example 4: Construction and Co-production Demonstration of an Integrated Seawater Electrolysis System

[0036] A flow cell electrolysis system was constructed using NiCo2Se4@VO as the anode and Ni2P / Co(PO3)2 as the cathode. Figure 4 (See Figures a-b). This system requires only 1.81 V of total voltage to achieve 1 A cm⁻¹. -2 It has been running stably for over 1200 hours. Figure 4 (Figure c). Post-treatment of the anolyte successfully crystallized KNO2 powder. Figure 4 (D-E diagrams), with a purity of approximately 83.78%, while the cathode continuously produces hydrogen. Example 5: Investigation of Reaction Mechanism

[0037] Through EPR ( Figure 5 (Figure a) and in-situ FTIR ( Figure 5 The e-h plot captured key intermediates, confirming the enrichment of *OH and its role in UOR. Using TMAH inhibitors and O 18 Isotope labeling experiment ( Figure 6 Figures a-d demonstrate that the UOR of NiCo2Se4@VO mainly follows the LOM, with its lattice oxygen directly participating in the reaction, which is the source of its ultra-high kinetics. Example 6: Verification of the universality of the LOM mechanism

[0038] like Figure 7 As shown in Figures a-c, NiCo2Se4@VO exhibits significantly higher activity than NiCo2Se4 in the OER, MOR, and HMFOR reactions, and its activity decreases more significantly after the addition of the TMAH inhibitor. Figure 7 The d-g plots show the comparison of the participation of LOM and AEM in various small molecule electro-oxidation reactions of NiCo2Se4@VO. In MOR and HMFOR, it is demonstrated that LOM plays a dominant role in various oxidation reactions on this catalyst during the catalytic process, accounting for more than 60%, while NiCo2Se4 accounts for only about 10% (mainly AEM), which shows that it has universality.

[0039] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the corresponding technical solutions to depart from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A composite nanostructure catalyst, characterized in that, The composite nanostructure catalyst was prepared by a method comprising the following steps: The nickel foam is soaked, washed and dried sequentially to obtain pretreated nickel foam; Precursor preparation: The pretreated nickel foam was placed in a mixed solution of Co(NO3)2·6H2O, Ni(NO3)2·6H2O and urea, and a hydrothermal reaction was carried out in an autoclave. After cooling, the reacted nickel foam was taken out, washed and dried to obtain NiCo-LDH precursor. Electrodeposition: NaVO3, NaNbO3 or NaTaO3 were respectively mixed with oxalic acid solution as electrolyte, and constant potential deposition was performed using a three-electrode system to load the corresponding metal-oxalate complex on the surface of the prepared NiCo-LDH precursor. Selenization treatment: Selenium powder is placed in the upstream zone of a dual-temperature zone tube furnace, and the NiCo-LDH precursor after electrodeposition is used as the object of selenization treatment to obtain the corresponding composite nanostructure catalysts NiCo2Se4@VO, NiCo2Se4@NbO or NiCo2Se4@TaO.

2. The composite nanostructure catalyst according to claim 1, characterized in that, The nickel foam was soaked in acetone and dilute hydrochloric acid in sequence.

3. The composite nanostructure catalyst according to claim 1, characterized in that, In the "precursor preparation" step, a hydrothermal reaction is carried out in an autoclave at 100~120°C for 10 hours.

4. The composite nanostructure catalyst according to claim 1, characterized in that, In the "electrodeposition" step, constant potential deposition is performed under working voltage of -0.8 to -1.2 V vs. RHE, wherein the working electrode is a NiCo-LDH precursor, the counter electrode is a graphite rod, and the reference electrode is an Ag / AgCl electrode.

5. The composite nanostructure catalyst according to claim 1, characterized in that, In the "electrodeposition" step, by controlling the ratio of metal V, Nb or Ta to oxalic acid in the electrodeposition process to be within the range of 1:1 to 1:2, composite nanostructure catalysts with different oxygen vacancy concentrations can be obtained after selenization treatment.

6. The composite nanostructure catalyst according to claim 5, characterized in that, In the "electrodeposition" step, the ratio of metal V to oxalic acid is adjusted to 1:2 during the electrodeposition process.

7. The application of the composite nanostructure catalyst of claim 1 for catalyzing small molecule electro-oxidation reactions, wherein the small molecule electro-oxidation reactions include UOR, MOR, or HMFOR.

8. A method for preparing composite nanostructured catalysts, characterized in that, The method includes the following steps: The nickel foam is soaked, washed and dried sequentially to obtain pretreated nickel foam; Precursor preparation: The pretreated nickel foam was placed in a mixed solution of Co(NO3)2·6H2O, Ni(NO3)2·6H2O and urea, and a hydrothermal reaction was carried out in an autoclave. After cooling, the reacted nickel foam was taken out, washed and dried to obtain NiCo-LDH precursor. Electrodeposition: NaVO3, NaNbO3 or NaTaO3 were respectively mixed with oxalic acid solution as electrolyte, and constant potential deposition was performed using a three-electrode system to load the corresponding metal-oxalate complex on the surface of the prepared NiCo-LDH precursor. Selenization treatment: Selenium powder is placed in the upstream zone of a dual-temperature zone tube furnace, and the NiCo-LDH precursor after electrodeposition is used as the object of selenization treatment to obtain the corresponding composite nanostructure catalysts NiCo2Se4@VO, NiCo2Se4@NbO or NiCo2Se4@TaO.

9. The method for preparing composite nanostructured catalysts according to claim 8, characterized in that, In the "electrodeposition" step, constant potential deposition is performed under working voltage of -0.8 to -1.2 V vs. RHE, wherein the working electrode is a NiCo-LDH precursor, the counter electrode is a graphite rod, and the reference electrode is an Ag / AgCl electrode.

10. The method for preparing composite nanostructured catalysts according to claim 8, characterized in that, In the "electrodeposition" step, by controlling the ratio of metal V, Nb or Ta to oxalic acid in the electrodeposition process to be within the range of 1:1 to 1:2, composite nanostructure catalysts with different oxygen vacancy concentrations can be obtained after selenization treatment.

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