Preparation of La / Bi co-doped nickel cobaltate material with hierarchical porous structure and application of La / Bi co-doped nickel cobaltate material in electro-catalytic urea oxidation

Abstract

The invention discloses preparation of a La / Bi co-doped nickel cobaltate material with a hierarchical porous structure and application of the La / Bi co-doped nickel cobaltate material in electro-catalytic urea oxidation. The preparation method comprises the following steps: firstly, growing metal hydroxide on foamed nickel in situ by adopting a constant-potential co-electrodeposition method, and then annealing in air to obtain a final product. The catalyst presents a nanosheet / nanoflower composite morphology, and the size of the nanoflower is about 1 [mu] m. The hierarchical porous structure and high specific surface area of the catalyst not only expose a large number of active sites, but also provide a rapid channel for the transfer of charges and substances, thereby facilitating the improvement of the electro-catalytic performance of the catalyst. By introducing lanthanide series metal and main group metal, compared with commercial RuO2, the La / Bi co-doped nickel cobaltate catalyst prepared by the preparation method disclosed by the invention shows better catalytic performance in a urea oxidation reaction.

Description

[0001] The present invention belongs to the field of electrocatalysis of urea-assisted water decomposition, and relates to the preparation of a La / Bi co-doped nickel cobalt oxide material with a hierarchical porous structure and its application in electrocatalytic urea oxidation. Background Art

[0002] Energy depletion and environmental problems caused by excessive fossil energy consumption have seriously threatened ecological security and human health. Driven by the "dual carbon" strategy, the development of efficient and clean alternative energy sources is urgent. Hydrogen, with its high energy density and zero carbon emissions, is considered the most promising alternative to fossil fuels. Currently, green hydrogen production is primarily achieved through renewable energy water electrolysis. However, its large-scale application is limited by the high theoretical potential (1.23 V vs. RHE) and slow kinetics of the anodic oxygen evolution reaction (OER), resulting in high energy consumption and costs for hydrogen production. Therefore, there is an urgent need to develop low-potential anodic oxidation reactions that can replace the OER and couple them with the hydrogen evolution reaction (HER) to achieve efficient electrolytic hydrogen production. The electrochemical urea oxidation reaction (UOR) provides an innovative approach to this end. This reaction converts urea into harmless products such as N2, CO2, and H2O, thereby purifying urea wastewater. Furthermore, its low theoretical potential (0.37 V vs. RHE) can replace the OER and, through coupling with the HER, simultaneously achieve efficient hydrogen production and energy conversion.

[0003] In recent years, urea electrooxidation catalysts have been primarily categorized into noble metal-based and non-noble metal-based catalysts. While noble metal-based catalysts (e.g., Pt and Ru) offer excellent performance, their high cost has limited their large-scale application. In contrast, non-noble metal-based catalysts (e.g., Ni- and Co-based materials) have attracted considerable attention due to their cost advantages. Ni-based catalysts, due to their high catalytic activity, are considered promising candidates for urea-assisted hydrogen production. Recent studies have demonstrated that the catalytic activity and product selectivity of electrochemically in situ generated NiOOH, the true active center in the UOR reaction, are highly dependent on the electronic coordination environment. However, a single active site alone is insufficient to synergistically optimize multistep reaction pathways. Consequently, multimetallic oxides, owing to their diverse active sites, tunable electronic structures, and significant synergistic effects, have attracted significant attention in the catalytic field. In particular, spinel nickel cobalt oxides, through interactions between different metals, can modulate the electronic structure of the active sites, optimize the adsorption of oxygen-containing species, and enhance catalyst performance. For example, Yan's team used a manganese (Mn) doping strategy to reduce the concentration of oxygen vacancies in the transition metal oxide nickel cobalt oxide, enhancing lattice oxygen stability and forming an Mn-O structure at adjacent octahedral positions, thereby significantly improving the activity and stability of nickel cobalt oxide. Therefore, the introduction of other heteroatoms into nickel cobalt oxide to synthesize an electrocatalyst in which the active site microenvironment is synergistically controlled by multiple metals is of great significance. Summary of the Invention

[0004] The purpose of the present invention is to provide a preparation of a La / Bi co-doped nickel cobalt oxide material with a hierarchical porous structure and its application in the electrocatalytic oxidation of urea. The present invention first adopts a constant potential co-electrodeposition method to in situ grow metal hydroxide on nickel foam, and then annealing treatment is carried out in air to obtain the final product. The catalyst has a nanosheet / nanoflower composite morphology, and the size of the nanoflower is about 1 μm. Its hierarchical porous structure and high specific surface area not only expose a large number of active sites on the catalyst, but also provide a fast channel for the transfer of charge and substance, which helps to improve the electrocatalytic performance of the catalyst. The introduction of lanthanide metals and main group metals makes the La / Bi doped nickel cobalt oxide catalyst prepared by the present invention show better catalytic performance in urea oxidation reaction compared with commercial RuO2.

[0005] The preparation method of the La / Bi co-doped nickel cobalt oxide material having a hierarchical porous structure of the present invention comprises the following steps: Step 1: Dissolve a certain amount of cobalt nitrate hexahydrate, nickel chloride hexahydrate, lanthanum nitrate, and bismuth nitrate in deionized water and ultrasonicate at room temperature for 30 min to prepare a homogeneous electrolyte.

[0006] Step 2: The pretreated NF was used as the working electrode, an Ag / AgCl electrode (1 M KCl) as the reference electrode, and a graphite rod as the counter electrode. Metal hydroxide (M-OH) precursors were synthesized by potentiostatic deposition at -1 V.

[0007] Step 3: The precursor was transferred to a tube furnace and calcined at 300 °C in air for 3 h with a heating rate of 1 °C / min to obtain a La / Bi co-doped NiCo2O4 catalyst with a nanosheet / nanoflower composite morphology.

[0008] In step 1, the molar amount of cobalt nitrate hexahydrate is 0.15 mmol, and the molar amount of nickel chloride hexahydrate is 0.15 mmol.

[0009] In step 1, the molar amount of lanthanum nitrate is 0.01 mmol, and the molar amount of bismuth nitrate is 0.002 mmol.

[0010] In step 2, the required nickel foam is obtained by the following method: cutting a piece of nickel foam of 1.0 cm × 1.5 cm, ultrasonically cleaning it with dilute hydrochloric acid, ethanol and water for multiple times, and finally drying it in a vacuum drying oven for use.

[0011] The application of the La / Bi co-doped nickel cobalt oxide material with a hierarchical porous structure of the present invention is to use the La / Bi co-doped nickel cobalt oxide material with a hierarchical porous structure as a catalyst to realize an electrocatalytic urea oxidation reaction under alkaline conditions.

[0012] Specifically, in a three-electrode system, La / Bi co-doped nickel cobalt oxide material was used as the working electrode (1.0 cm × 1.0 cm), Hg / HgO was used as the reference electrode, and Pt sheet was used as the counter electrode to test the performance of the catalyst in catalyzing the urea oxidation reaction under alkaline conditions. In addition, La / Bi co-doped nickel cobalt oxide material was used as the anode electrocatalyst, and commercial Pt / C loaded on nickel foam was used as the cathode catalyst for urea-assisted total hydrolysis reaction. Linear sweep voltammetry tests were performed at a scan rate of 5 mV / s in the potential range of 1.0 V -1.8 V (vs. RHE) and compared with commercial RuO2 to explore the performance changes. In addition, in a three-electrode system, at 50 mA / cm 2 The stability test was carried out at a constant current density of 90 h; in a two-electrode system, at 50 mA / cm 2 The stability test was carried out at a constant current density of 200 h.

[0013] The electrolyte is a 1 mol / L KOH solution, and the molar ratio of KOH to CO(NH2)2 is 1:0.33.

[0014] The beneficial effects of the present invention are embodied in: The La / Bi co-doped nickel cobaltate catalyst with a hierarchical porous structure prepared by the present invention adopts a simple constant potential co-electrodeposition method combined with annealing treatment. It provides a simple method for synthesizing multi-metal doped oxides. The present invention introduces lanthanide metals and main group metals into nickel cobaltate, and through the synergistic effect between the metals, optimizes the electronic structure of the active site, thereby obtaining enhanced urea oxidation performance. In addition, the special hierarchical porous structure and its high specific surface area not only provide abundant active sites for the catalytic reaction, but also provide a rapid transfer channel for charge and substance, accelerating the progress of the urea oxidation reaction. The catalyst of the present invention exhibits significantly enhanced catalytic activity in an actual electrochemical full hydrolysis device. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments. It should be noted that these drawings do not limit the scope of the present invention, but are only used as an explanation of the technical solution of the present invention.

[0016] Figure 1 This is the X-ray diffraction pattern (XRD) of the nickel cobalt oxide catalyst prepared in Example 1.

[0017] Figure 2 This is the X-ray photoelectron spectroscopy (XPS) of the nickel cobalt oxide catalyst prepared in Example 1.

[0018] Figure 3This is a comparison of the linear sweep voltammetry (LSV) curves of the nickel cobalt oxide catalyst prepared in Example 1 and commercial RuO2 / NF in 1 mol / L KOH + 0.33 mol / L Urea solution.

[0019] Figure 4 This is the Tafel slope plot of the nickel cobalt oxide catalyst prepared in Example 1.

[0020] Figure 5 This is the X-ray diffraction pattern (XRD) of the La / Bi co-doped nickel cobaltate catalyst prepared in Example 2.

[0021] Figure 6 X-ray photoelectron spectroscopy (XPS) of La / Bi co-doped nickel cobaltate prepared in Example 2.

[0022] Figure 7 This is a scanning electron micrograph (SEM) of the La / Bi co-doped nickel cobaltate prepared in Example 2.

[0023] Figure 8 This is a transmission electron microscopy (TEM) image of La / Bi co-doped nickel cobalt oxide prepared in Example 2.

[0024] Figure 9 This is a comparison of the linear sweep voltammetry (LSV) curves of La / Bi co-doped nickel cobaltate prepared in Example 2 and commercial RuO2 / NF in 1 mol / L KOH + 0.33 mol / L Urea solution.

[0025] Figure 10 This is the Tafel slope plot of La / Bi co-doped nickel cobaltate prepared in Example 2.

[0026] Figure 11 The La / Bi co-doped nickel cobalt oxide prepared in Example 2 was placed in a 1 mol / L KOH + 0.33 mol / L Urea solution at 50 mA / cm 2 Chronovoltage curve at current density.

[0027] Figure 12 This is a linear sweep voltammogram of a urea-assisted full hydrolysis electrolyzer consisting of the La / Bi co-doped nickel cobaltate catalyst prepared in Example 2 and the Pt / C catalyst supported on nickel foam as the anode and cathode, respectively, in a 1 mol / L KOH + 0.33 mol / L Urea solution.

[0028] Figure 13The La / Bi co-doped nickel cobaltate catalyst prepared in Example 2 and the Pt / C catalyst supported on nickel foam were used as the anode and cathode, respectively, in a urea-assisted full hydrolysis electrolytic cell in a 1 mol / L KOH + 0.33 mol / L Urea solution at 50 mA / cm 2 Chronovoltage curve at current density.

[0029] Figure 14 Comparison of the linear sweep voltammetry (LSV) curves of the La / Bi co-doped nickel cobaltate catalyst prepared in Example 3 and commercial RuO2 / NF in 1 mol / L KOH + 0.33 mol / L Urea solution.

[0030] Figure 15 This is the Tafel slope plot of the La / Bi co-doped nickel cobaltate catalyst prepared in Example 3.

[0031] Figure 16 Comparison of the linear sweep voltammetry (LSV) curves of the La / Bi co-doped nickel cobaltate catalyst prepared in Example 4 and commercial RuO2 / NF in 1 mol / L KOH + 0.33 mol / L Urea solution.

[0032] Figure 17 This is the Tafel slope plot of the La / Bi co-doped nickel cobaltate catalyst prepared in Example 4. DETAILED DESCRIPTION

[0033] The technical solutions of the present invention are further described below in conjunction with specific embodiments. It should be noted that the specific description of the embodiments below is only used to illustrate the synthesis, characterization and performance of the catalyst and should not be understood as limiting the present invention. Those embodiments not directly mentioned in this article may still be obtained by combining these technical solutions. Example 1:

[0034] The nickel cobalt oxide (NiCo2O4) catalyst prepared in this embodiment includes the following steps: 1. Cut a piece of commercial nickel foam (1.0 cm × 1.5 cm), clean it with 3 mol / L dilute hydrochloric acid, ethanol, and deionized water ultrasonically for 10 min, and finally dry it in a vacuum drying oven for 12 h.

[0035] 2. Weigh 0.15 mmol of cobalt nitrate hexahydrate and 0.15 mmol of nickel chloride hexahydrate into a beaker, add 50 mL of deionized water, and ultrasonicate for 30 min.

[0036] 3. A three-electrode system was used with clean nickel foam as the working electrode, Ag / AgCl as the reference electrode, and a carbon rod as the counter electrode. Co-electrodeposition was performed at a constant potential of -1 V for 10 min. The resulting precursor (NiCo-OH) was rinsed several times with deionized water and dried in a vacuum drying oven for 12 h.

[0037] 4. Place the NiCo-OH precursor in a tube furnace, heat it to 300 °C at a heating rate of 1 °C / min in an air atmosphere, and anneal it at this temperature for 3 h to obtain the nickel cobalt oxide electrocatalyst.

[0038] Figure 1 This is the XRD pattern of the nickel cobalt oxide electrocatalyst prepared in Example 1. It can be seen from the figure that the diffraction peak of the sample corresponds to NiCo2O4 (PDF#20-0781), indicating the successful synthesis of the nickel cobalt oxide electrocatalyst.

[0039] Figure 2 The XPS spectrum of the nickel cobalt oxide electrocatalyst prepared in Example 1 shows that the sample is composed of three elements: Ni, Co, and O, which is consistent with the XRD results, indicating that the nickel cobalt oxide electrocatalyst was successfully synthesized.

[0040] Figure 3 This is a comparison of the linear sweep voltammetry (LSV) curves of the nickel cobalt oxide catalyst prepared in Example 1 and commercial RuO2 / NF in 1 mol / L KOH + 0.33 mol / L Urea solution. It can be seen that compared with the commercial RuO2 / NF, the nickel cobalt oxide catalyst prepared in Example 1 has a lower onset potential and a driving current of 100 mA / cm 2 The current density required a voltage of 1.38 V, which is lower than that of commercial RuO2 / NF, indicating that the nickel cobalt oxide catalyst prepared in Example 1 has better urea oxidation performance.

[0041] Figure 4 This is a Tafel slope diagram of the nickel cobalt oxide catalyst prepared in Example 1. It can be seen that the nickel cobalt oxide catalyst prepared in Example 1 has a smaller Tafel slope (85.7 mV / dec), indicating that its kinetics is faster. Example 2:

[0042] This embodiment prepares a La / Bi co-doped nickel cobalt oxide catalyst having a hierarchical porous structure, comprising the following steps: 1. Cut a piece of commercial nickel foam (1.0 cm × 1.5 cm), clean it with 3 mol / L dilute hydrochloric acid, ethanol, and deionized water ultrasonically for 10 min, and finally dry it in a vacuum drying oven for 12 h.

[0043] 2. Weigh 0.15 mmol of cobalt nitrate hexahydrate, 0.15 mmol of nickel chloride hexahydrate, 0.01 mmol of lanthanum nitrate, and 0.002 mmol of bismuth nitrate into a beaker, add 50 mL of deionized water, and sonicate for 30 min.

[0044] 3. A three-electrode system was used with clean nickel foam as the working electrode, Ag / AgCl as the reference electrode, and a carbon rod as the counter electrode. Co-electrodeposition was performed at a constant potential of -1 V for 10 min. The resulting precursor (M-OH) was rinsed several times with deionized water and dried in a vacuum drying oven for 12 h.

[0045] 4. The M-OH precursor was placed in a tube furnace, heated to 300°C at a heating rate of 1°C / min in an air atmosphere, and annealed at this temperature for 3 h to obtain a La / Bi co-doped nickel cobalt oxide catalyst with a hierarchical porous structure.

[0046] Figure 5 This is the XRD pattern of the La / Bi co-doped nickel cobalt oxide catalyst with a hierarchical porous structure prepared in Example 2. It can be seen from the figure that the diffraction peak of the sample corresponds to NiCo2O4 (PDF#20-0781), and the introduction of trace elements does not change the physical phase of the catalyst, indicating that the La / Bi co-doped nickel cobalt oxide catalyst was successfully synthesized.

[0047] Figure 6 The XPS spectrum of the La / Bi co-doped nickel cobalt oxide catalyst with a hierarchical porous structure prepared in Example 2 shows that the sample is composed of five elements: Ni, Co, O, La, and Bi, which is consistent with the XRD results, indicating that the La / Bi co-doped nickel cobalt oxide catalyst was successfully synthesized.

[0048] Figure 7 This is an SEM image of the La / Bi co-doped nickel cobalt oxide catalyst with a hierarchical porous structure prepared in Example 2. It can be seen that the sample presents a nanosheet / nanoflower composite morphology, and the nanoflower has a diameter of about 1 μm.

[0049] Figure 8 This is a TEM image of the La / Bi co-doped nickel cobalt oxide catalyst with a hierarchical porous structure prepared in Example 2. It can be seen that there are a large number of evenly distributed pores on the nanosheets with a diameter of about 2-5 nm, indicating that the La / Bi co-doped nickel cobalt oxide catalyst prepared in Example 2 has a porous structure.

[0050] Figure 9This is a comparison of the linear sweep voltammetry (LSV) curves of La / Bi co-doped nickel cobalt oxide prepared in Example 2 and commercial RuO2 / NF in 1 mol / L KOH + 0.33 mol / L Urea solution. It can be seen that compared with the commercial RuO2 / NF, the La / Bi co-doped nickel cobalt oxide catalyst prepared in Example 2 has a lower onset potential and is driven at 100 mA / cm 2 The current density requires a voltage of 1.33 V, which is lower than that of commercial RuO2 / NF, indicating that the La / Bi co-doped nickel cobaltate catalyst prepared in Example 2 has better urea oxidation performance.

[0051] Figure 10 This is the Tafel slope plot of the La / Bi co-doped nickel cobalt oxide prepared in Example 2. It can be seen that the La / Bi co-doped nickel cobalt oxide catalyst prepared in Example 2 has a smaller Tafel slope (60.3 mV / dec), indicating that its kinetics is faster.

[0052] Figure 11 The La / Bi co-doped nickel cobalt oxide prepared in Example 2 was placed in a 1 mol / L KOH + 0.33 mol / L Urea solution at 50 mA / cm 2 The chronovoltage curve at the current density of 50 mA / cm 2 It can operate stably for 90 h at a constant current density, indicating that it has good stability.

[0053] Figure 12 The linear sweep voltammogram of a urea-assisted full hydrolysis electrolytic cell composed of the La / Bi co-doped nickel cobaltate catalyst prepared in Example 2 and the Pt / C catalyst supported on nickel foam as the anode and cathode, respectively, in a 1 mol / L KOH + 0.33 mol / L Urea solution. The electrolytic cell composed of the La / Bi co-doped nickel cobaltate catalyst prepared in Example 2 and the commercial Pt / C / NF obtained a 100 mA / cm 2 The current density only requires a cell voltage of 1.45 V, which is lower than that of the electrolyzer composed of commercial RuO2 / NF and commercial Pt / C / NF, indicating that the La / Bi co-doped nickel cobaltate catalyst prepared in Example 2 can be effectively used for urea-assisted full hydrolysis to produce hydrogen.

[0054] Figure 13 The La / Bi co-doped nickel cobaltate catalyst prepared in Example 2 and the Pt / C catalyst supported on nickel foam were used as the anode and cathode, respectively, in a urea-assisted full hydrolysis electrolytic cell in a 1 mol / L KOH + 0.33 mol / L Urea solution at 50 mA / cm2 The chronovoltage curve at the current density of 50 mA / cm 2 After continuous operation for 200 h at a current density of 1.5 wt %, the voltage still retained 88% of the initial voltage, indicating its excellent stability in urea-assisted perhydrolysis. Example 3:

[0055] The La / Bi co-doped nickel cobaltate catalyst was prepared according to Example 2, except that the mass of bismuth nitrate was changed to 0.002 mmol, while other conditions remained unchanged.

[0056] Figure 14 This is a comparison of the linear sweep voltammetry (LSV) curves of the La / Bi co-doped nickel cobalt oxide catalyst prepared in Example 3 and commercial RuO2 / NF in 1 mol / L KOH + 0.33 mol / L Urea solution. It can be seen that compared with the commercial RuO2 / NF, the La / Bi co-doped nickel cobalt oxide catalyst prepared in Example 3 has a lower onset potential and is driven at 100 mA / cm 2 The current density required a voltage of 1.36 V, which is much lower than that of commercial RuO2 / NF, indicating that the La / Bi co-doped nickel cobaltate catalyst prepared in Example 3 has better urea oxidation performance.

[0057] Figure 15 This is the Tafel slope plot of the La / Bi co-doped nickel cobalt oxide catalyst prepared in Example 3. It can be seen that the La / Bi co-doped nickel cobalt oxide catalyst prepared in Example 3 has a smaller Tafel slope (63.5 mV / dec), indicating that its kinetics is faster. Example 4:

[0058] The La / Bi co-doped nickel cobaltate catalyst was prepared according to Example 2, except that the molar amount of bismuth nitrate was changed to 0.001 mmol, and other conditions remained unchanged.

[0059] Figure 16 This is a comparison of the linear sweep voltammetry (LSV) curves of the La / Bi co-doped nickel cobalt oxide catalyst prepared in Example 4 and commercial RuO2 / NF in 1 mol / L KOH + 0.33 mol / L Urea solution. It can be seen that compared with the commercial RuO2 / NF, the La / Bi co-doped nickel cobalt oxide catalyst prepared in Example 4 has a higher onset potential than the commercial RuO2 / NF, and the driving current is 100 mA / cm 2 The voltage required for the current density is much higher than that of commercial RuO2 / NF, indicating that the urea oxidation performance of the La / Bi co-doped nickel cobaltate catalyst prepared in Example 4 is greatly reduced.

[0060] Figure 17This is the Tafel slope plot of the La / Bi co-doped nickel cobalt oxide catalyst prepared in Example 4. It can be seen that the La / Bi co-doped nickel cobalt oxide catalyst prepared in Example 4 has a large Tafel slope (195.3 mV / dec), indicating that its kinetics are slow.

[0061] By analyzing the above examples, and through the results of Examples 1, 2, and 4, we can determine that La / Bi co-doping can accelerate the urea oxidation reaction kinetics of the nickel cobalt oxide catalyst and improve its urea oxidation performance. The results of Examples 2 to 4 show that the La / Bi doping ratio also affects the performance of the catalyst, and an improper ratio will significantly reduce the performance. The performance is best when the La / Bi ratio is 0.2 mmol:0.04 mmol, that is, Example 2 has the best urea oxidation performance. Compared with commercial RuO2 / NF, the La / Bi co-doped nickel cobalt oxide catalyst prepared in Example 2 requires the smallest voltage value to reach the same current density, and also has the fastest kinetics (the smallest Tafel slope).

Claims

1. A method for preparing a La / Bi co-doped nickel cobalt oxide material (La / Bi-NiCo2O4) with a hierarchical porous structure, comprising the following steps: Step 1: Dissolve a certain amount of cobalt nitrate hexahydrate, nickel chloride hexahydrate, lanthanum nitrate, and bismuth nitrate in deionized water and ultrasonicate at room temperature for 30 min to prepare a homogeneous electrolyte.

2. Step 2: Using the pretreated NF as the working electrode, an Ag / AgCl electrode (1 M KCl) as the reference electrode, and a carbon rod as the counter electrode, a metal hydroxide (M-OH) precursor was synthesized by potentiostatic co-electrodeposition at a potential of -1 V.

3. Step 3: Transfer the precursor to a tube furnace and calcine it at 300 °C in air for 3 h with a heating rate of 1 °C / min to obtain a La / Bi co-doped NiCo2O4 catalyst with a nanosheet / nanoflower composite morphology.

4. The preparation method according to claim 1, wherein: In step 1, the molar amount of cobalt nitrate hexahydrate is 0.15 mmol, and the molar amount of nickel chloride hexahydrate is 0.15 mmol.

5. The preparation method according to claim 2, wherein: In step 1, the molar amount of lanthanum nitrate is 0.01 mmol, and the molar amount of bismuth nitrate is 0.002 mmol.

6. The preparation method according to claim 2, wherein: In step 2, the required nickel foam is obtained by the following method: cutting a piece of nickel foam of 1.0 cm × 1.5 cm, ultrasonically cleaning it with dilute hydrochloric acid, ethanol and water for multiple times, and finally drying it in a vacuum drying oven for use.

7. Use of La / Bi co-doped nickel cobalt oxide having a hierarchical porous structure prepared by the preparation method according to any one of claims 1 to 4, characterized in that: The La / Bi co-doped nickel cobaltate with a hierarchical porous structure is used as a catalyst to realize a urea electro-oxidation catalytic reaction under alkaline conditions.

8. The use according to claim 5, characterized in that: In a three-electrode system, La / Bi co-doped nickel cobalt oxide catalyst with a hierarchical porous structure was used as the working electrode, Hg / HgO as the reference electrode, and platinum sheet as the counter electrode to catalyze the urea oxidation reaction in alkaline electrolyte.

9. The use according to claim 6, characterized in that: The alkaline electrolyte is a 1 mol / L KOH solution, and the molar ratio of KOH to CO(NH2)2 is 1:0.33.

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