Preparation of binary composite structure molybdenum-doped nickel-cobalt prussian blue analog and its application in electrocatalytic oxidation of urea

Abstract

The application discloses a preparation of a binary composite structure molybdenum-doped nickel-cobalt Prussian blue analogue and application of the binary composite structure molybdenum-doped nickel-cobalt Prussian blue analogue in electrocatalytic oxidation of urea. The application adopts a simple hydrothermal method, uses a foamed nickel as a nickel source and a conductive substrate, and prepares a molybdenum-doped nickel-cobalt Prussian blue analogue electrocatalyst in-situ grown on the foamed nickel. The structure of the catalyst is composed of a bottom plate structure and a surface point-decorated cube, and the special structure can not only increase active sites of the catalyst and improve overall performance of the catalyst, but also help to enhance the stability of the overall catalyst. The doping of the heteroatom molybdenum makes the nickel-cobalt Prussian blue analogue catalyst prepared in the application have higher catalytic performance on the urea oxidation reaction compared with a commercial RuO2 / NF.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of electrocatalysis of urea-assisted water splitting, and particularly relates to a preparation of a binary composite structure of molybdenum-doped nickel-cobalt prussian blue analog and application thereof in electrocatalytic oxidation of urea. BACKGROUND

[0002] Energy crisis and environmental pollution make it urgent to develop clean and efficient new energy systems. Compared with other fuels, hydrogen molecules have a very high energy density, and the product after combustion is only pollution-free water, so they are considered one of the most promising energies. Producing hydrogen (H2) through water splitting is an environmentally friendly method, however, due to the thermodynamically slow oxygen evolution reaction (OER) on the anode, the efficiency of hydrogen production is severely limited, which leads to high energy loss and expensive production cost of water electrolysis. Therefore, it is urgent to develop high-performance electrocatalysts and alternative anode oxidation reactions to reduce the driving voltage and promote its practical application.

[0003] In the electrochemical overall water electrolysis device, urea oxidation reaction (UOR) is considered a very promising alternative to anode OER, because it requires much lower cell voltage (0.37 V) than OER (1.23 V), which helps to save energy and improve the efficiency of hydrogen production. At the same time, urea electrolysis based on UOR is also a way to achieve urea-containing wastewater purification. Urea-assisted water splitting includes two half-reactions:

[0004] Anode (UOR): CO(NH2)2+6OH - →N2+5H2O+CO2+6e - (1)

[0005] Cathode (HER): 6H2O+6e - →3H2+6OH - (2)

[0006] However, due to the 6e - transfer process, the kinetics of UOR is relatively slow. Therefore, it is necessary to develop effective catalysts to promote urea-assisted water splitting.

[0007] So far, noble metal-based catalysts, such as ruthenium dioxide and iridium dioxide, have shown effective catalytic performance for OER and UOR, but their large-scale practical application is hindered due to their high cost and rarity on earth. Recently, various nickel-based catalysts are considered to be more promising candidate materials for UOR. In this regard, Prussian blue (PB) and its analogues (PBAs) are promising coordination polymers with adjustable composition and open framework. However, their poor intrinsic electrochemical activity and electrical conductivity hinder the overall catalytic activity of water splitting. Heteroatom doping engineering is an effective strategy to further improve the activity of electrocatalysts by adjusting the electronic structure, increasing the number of active sites and optimizing the formation of intermediate products. For example, Xu et al. reported in situ growth of dendritic Mo-doped Ni3S2 nanoforest catalyst on nickel foam, which only requires a voltage of 1.45 V to obtain a current density of 10 mA cm -2 for urea-assisted water splitting and exhibits good durability. By precisely controlling Mo doping to adjust the electronic structure, a hierarchical dendritic nanostructure is formed, which can optimize the absorption energy of surface reactant molecules and promote the exposure of abundant active sites. Therefore, optimizing the structure and active sites of the catalyst is crucial to improve the electrocatalytic performance. SUMMARY

[0008] The present application provides a binary composite structure molybdenum-doped nickel-cobalt prussian blue analog (Mo-NiCo PBA / NF) grown in situ on nickel foam, and uses it as a catalyst to achieve high-efficiency urea oxidation reaction.

[0009] The present application uses a simple hydrothermal method to prepare a molybdenum-doped nickel-cobalt prussian blue analog electrocatalyst grown in situ on nickel foam using nickel foam as both a nickel source and a conductive substrate. The structure of the catalyst is composed of a plate-like structure at the bottom and a surface-decorated rounded cube, which not only increases the active sites of the catalyst and improves its overall performance, but also helps to enhance the stability of the catalyst. The doping of heteroatom Mo makes the Mo-NiCo PBA / NF nanocatalyst prepared by the present application exhibit higher catalytic performance for urea oxidation reaction compared with commercial RuO2 / NF.

[0010] The preparation method of the binary composite structure molybdenum-doped nickel-cobalt prussian blue analog of the present application comprises the following steps:

[0011] Step 1: A certain amount of surfactant dextran-20, citric acid monohydrate and molybdenum salt are placed in a beaker, and 300 mL of deionized water is added to dissolve, denoted as solution A;

[0012] Step 2: weigh a certain amount of K3[Co(CN)6] in a beaker, dissolve in 200 mL of deionized water, and mark as solution B;

[0013] Step 3: add solution A drop by drop to solution B under stirring, and mix well;

[0014] Step 4: transfer 30 mL of the mixed solution into a 40 mL Teflon-lined autoclave with pretreated nickel foam, and keep at 60-100℃ for 10-14 hours; after the reaction is completed, naturally cool to room temperature, wash several times with deionized water, and dry in an oven to obtain a binary composite structure molybdenum-doped nickel-cobalt Prussian blue analogue Mo-NiCoPBA / NF. The pretreated nickel foam electrode serves as both a nickel source and a conductive substrate.

[0015] In step 1, the molar amount of dextran-20 is 0.1 mmol, and the molar amount of citric acid monohydrate is 2.1 mmol.

[0016] In step 1, the molybdenum salt is Na2MoO4·2H2O, and the molar amount is 0.01-0.1 mmol, preferably 0.05 mmol.

[0017] In step 2, the molar amount of K3[Co(CN)6] is 0.5 mmol.

[0018] In step 4, the pretreated nickel foam is obtained by the following method: cut a piece of nickel foam electrode with appropriate size, and clean with dilute hydrochloric acid solution, acetone and deionized water under ultrasonic, and dry in an oven for standby use.

[0019] The application of the binary composite structure molybdenum-doped nickel-cobalt Prussian blue analogue is to use the binary composite structure molybdenum-doped nickel-cobalt Prussian blue analogue as a catalyst to realize the electrocatalytic oxidation reaction of urea under alkaline conditions.

[0020] Specifically, a standard three-electrode system is used, and the in-situ grown Mo-NiCo PBA / NF (1.0 cm x 1.0 cm) is directly used as a working electrode, a platinum sheet electrode is used as a counter electrode, and a Hg / HgO electrode is used as a reference electrode. The urea oxidation performance of the Mo-NiCo PBA / NF catalyst is tested in an alkaline electrolyte, and the Mo-NiCo PBA / NF is used as an anode electrocatalyst, and a commercial Pt / C loaded on nickel foam is used as a cathode electrocatalyst and applied to a urea-assisted full-hydrolysis device. Linear sweep voltammetry test is carried out at a scan rate of 5 mV / s in a potential range of 0.2 V-1.0 V (relative to Hg / HgO electrode), and compared with a commercial RuO2 to explore the change of electrocatalytic performance; and a stability test is carried out at a constant current density for 50 h. -2 A stability test is carried out at a constant current density for 50 h.

[0021] The alkaline electrolyte is a 1 mol / L KOH solution, and the molar ratio of KOH to CO(NH2)2 is 1:0.33.

[0022] The beneficial effects of the present application are embodied in:

[0023] The molybdenum-doped nickel-cobalt Prussian blue analogue urea oxidation catalyst with a binary composite structure grown in-situ on a foam nickel is synthesized by a simple hydrothermal method, and provides a simple and convenient method for synthesizing Prussian blue analogues. The foam nickel is directly used as a nickel source without additional addition of nickel salt, and a molybdenum salt is added for heteroatom doping, so that the electronic structure is optimized, thereby exhibiting excellent catalytic performance. The synergistic effect between different metal centers is conducive to improving the activity of nickel sites and accelerating the complete oxidation of urea. The catalyst of the present application exhibits excellent catalytic performance in an actual electrochemical water splitting device. BRIEF DESCRIPTION OF DRAWINGS

[0024] The technical solutions of the present application will be further described below in combination with the drawings and examples, and it should be noted that these drawings do not limit the scope of the present application, but only serve as an explanation of the technical solutions of the present application.

[0025] Figure 1 X-ray diffraction image (XRD) of the nickel-cobalt Prussian blue analogue catalyst prepared in Example 1.

[0026] Figure 2 X-ray photoelectron spectroscopy (XPS) of the nickel-cobalt Prussian blue analogue catalyst prepared in Example 1.

[0027] Figure 3 Linear sweep voltammogram of the nickel-cobalt Prussian blue analogue catalyst prepared in Example 1 and commercial RuO2 / NF loaded on foam nickel in a 1 mol / L KOH+0.33 mol / L CO(NH2)2 mixed solution.

[0028] Figure 4 Tafel slope plot of the nickel-cobalt Prussian blue analogue catalyst prepared in Example 1.

[0029] Figure 5 Scanning electron microscope image (SEM) of the binary composite structure molybdenum-doped nickel-cobalt Prussian blue analogue catalyst prepared in Example 2.

[0030] Figure 6 X-ray diffraction image (XRD) of the binary composite structure molybdenum-doped nickel-cobalt Prussian blue analogue catalyst prepared in Example 2.

[0031] Figure 7The image shows the X-ray photoelectron spectroscopy (XPS) spectrum of the molybdenum-doped nickel-cobalt Prussian blue analog catalyst with a binary composite structure prepared in Example 2. The inset is a magnified view of the region from 225 to 244 eV.

[0032] Figure 8 Linear scan voltammetry of the binary composite molybdenum-doped nickel-cobalt Prussian blue analog catalyst prepared in Example 2 and commercial RuO2 / NF supported on nickel foam in a mixed solution of 1 mol / L KOH + 0.33 mol / L CO(NH2)2.

[0033] Figure 9 Tafel slope diagram of the binary composite molybdenum-doped nickel-cobalt Prussian blue analog catalyst prepared in Example 2.

[0034] Figure 10 The binary composite molybdenum-doped nickel-cobalt Prussian blue analog catalyst prepared in Example 2 was reacted with a 1 mol / L KOH + 0.33 mol / L CO(NH2)2 mixed solution at 10 mA / cm⁻¹. -2 The timing voltage curve of constant current density operation.

[0035] Figure 11 The linear sweep voltammetric curves of a urea-assisted total hydrolysis electrolyzer in a 1 mol / L KOH + 0.33 mol / L CO(NH2)2 mixed solution were obtained by using the binary composite molybdenum-doped nickel-cobalt Prussian blue analog catalyst prepared in Example 2 and a commercial Pt / C / NF supported on nickel foam as the anode and cathode, respectively.

[0036] Figure 12 The binary composite molybdenum-doped nickel-cobalt Prussian blue analog catalyst prepared in Example 2 and a commercial Pt / C / NF supported on nickel foam were used as the anode and cathode, respectively, to form a urea-assisted total hydrolysis electrolyzer. The electrolyzer was operated in a 1 mol / L KOH + 0.33 mol / L CO(NH2)2 mixed solution at 10 mA / cm². -2 The timing voltage curve of constant current density operation.

[0037] Figure 13 Linear scan voltammetry of the binary composite molybdenum-doped nickel-cobalt Prussian blue analog catalyst prepared in Example 3 and commercial RuO2 / NF supported on nickel foam in a mixed solution of 1 mol / L KOH + 0.33 mol / L CO(NH2)2.

[0038] Figure 14 Tafel slope diagram of the binary composite molybdenum-doped nickel-cobalt Prussian blue analog catalyst prepared in Example 3.

[0039] Figure 15 Linear sweep voltammograms of the binary composite structure molybdenum-doped nickel cobalt Prussian blue analog catalyst prepared in Example 4 and commercial RuO2 / NF supported on foam nickel in 1 mol / L KOH + 0.33 mol / L CO(NH2)2 mixed solution.

[0040] Figure 16 Tafel slope plot of the binary composite structure molybdenum-doped nickel cobalt Prussian blue analog catalyst prepared in Example 4. DETAILED DESCRIPTION

[0041] The technical solutions of the present application are further described below in combination with specific examples. It should be noted that the following specific description of the examples is only used to illustrate the synthesis, characterization and performance of the catalyst, and should not be understood as limiting the present application. Those examples not directly mentioned in the text can still be combined to obtain the technical solutions.

[0042] Example 1:

[0043] The nickel cobalt Prussian blue analog catalyst grown in situ on foam nickel in this example includes the following steps:

[0044] 1. A piece of NF (2.0 cm x 3.0 cm) was ultrasonically cleaned in 3 mol / L dilute hydrochloric acid solution, acetone and deionized water for 15 minutes each.

[0045] 2. 0.1 mmol of dextran-20 and 2.1 mmol of citric acid monohydrate were dissolved in 300 mL of deionized water (solution A).

[0046] 3. The mixed solution was added dropwise to 200 mL of deionized water containing 0.5 mmol of K3[Co(CN)6] (solution B).

[0047] 4. 30 mL of the mixed solution was transferred to a 40 mL polytetrafluoroethylene lined autoclave containing a piece of pretreated NF, and kept at 80°C for 10 h to obtain the final NiCo PBA / NF electrocatalyst.

[0048] Figure 1 XRD pattern of the NiCo PBA / NF electrocatalyst prepared in Example 1, from which it can be seen that the XRD diffraction peaks of the sample correspond to Ni3(Co(CN)6)2(H2O) 12 (PDF #89-3738), indicating the successful synthesis of nickel cobalt Prussian blue analog.

[0049] Figure 2The XPS chart of the NiCo PBA / NF electrocatalyst prepared in Example 1 can be seen from the chart that there are Ni, Co, C, N, O elements in the catalyst, which corresponds to the XRD chart, indicating the successful synthesis of nickel-cobalt prussian blue analogues.

[0050] Figure 3 The linear sweep voltammograms of the NiCo PBA / NF electrocatalyst prepared in Example 1 and the commercial RuO2 loaded on nickel foam (commercial RuO2 / NF) in a mixed solution of 1 mol / L KOH + 0.33 mol / L CO(NH2)2 can be seen that the NiCo PBA / NF electrocatalyst prepared in Example 1 has a lower starting potential compared with the commercial RuO2 / NF, and only needs a voltage of 1.38 V to drive a large current density of 100 mA cm -2 -2, which is 140 mV lower than the commercial RuO2 / NF, indicating that the NiCo PBA / NF electrocatalyst prepared in Example 1 has better urea oxidation performance.

[0051] Figure 4 The Tafel curve chart of the NiCo PBA / NF electrocatalyst prepared in Example 1 can be seen that the Mo-NiCo PBA / NF catalyst has a smaller Tafel slope (18.81 mV dec -1 -1), indicating that it has faster reaction kinetics.

[0052] Example 2:

[0053] In this example, a molybdenum-doped nickel-cobalt prussian blue analogue catalyst with a binary composite structure grown in situ on nickel foam is prepared, which comprises the following steps:

[0054] 1. A piece of NF (2.0 cm x 3.0 cm) is ultrasonically cleaned in 3 mol / L dilute hydrochloric acid solution, acetone and deionized water for 15 minutes each.

[0055] 2. 0.1 mmol of dextran-20, 2.1 mmol of citric acid monohydrate and 0.05 mmol of Na2MoO4·2H2O are dissolved in 300 mL of deionized water (solution A).

[0056] 3. The mixed solution is added dropwise to 200 mL of deionized water containing 0.5 mmol of K3[Co(CN)6] (solution B).

[0057] 4. 30 mL of the mixed solution is transferred to a 40 mL polytetrafluoroethylene-lined autoclave, which contains a piece of pretreated NF, and is kept at 80°C for 10 h to obtain the final Mo-NiCo PBA / NF electrocatalyst.

[0058] Figure 5SEM image of Mo-NiCo PBA / NF electrocatalyst prepared in Example 2, from which it can be seen that the structure of Mo-NiCo PBA / NF is composed of plate-like structure at the bottom and surface-decorated rounded cubes.

[0059] Figure 6 XRD image of Mo-NiCo PBA / NF electrocatalyst prepared in Example 2, from which it can be seen that the XRD diffraction peaks of the sample correspond to Ni3(Co(CN)6)2(H2O) 12 (PDF #89-3738), indicating the successful synthesis of nickel-cobalt Prussian blue analogues, while it can be found that the introduction of trace amounts of molybdenum elements does not change the main crystal structure of nickel-cobalt Prussian blue analogues during the reaction process.

[0060] Figure 7 XPS image of Mo-NiCo PBA / NF electrocatalyst prepared in Example 2, from which it can be seen that there is molybdenum element in the catalyst, and the XRD image shows that we have successfully prepared a molybdenum-doped nickel-cobalt Prussian blue analogue catalyst.

[0061] Figure 8 Linear sweep voltammogram of Mo-NiCo PBA / NF electrocatalyst prepared in Example 2 and commercial RuO2 / NF in 1 mol / L KOH + 0.33 mol / L CO(NH2)2 mixed solution, it can be seen that compared with commercial RuO2 / NF, Mo-NiCo PBA / NF electrocatalyst prepared in Example 2 has a higher current density at the same potential, and a large current density of 100 mA cm -2 -2 is required, which is 180 mV lower than that of commercial RuO2 / NF, indicating that Mo-NiCo PBA / NF electrocatalyst prepared in Example 2 has better electrocatalytic performance in urea oxidation.

[0062] Figure 9 Tafel curve of Mo-NiCo PBA / NF electrocatalyst prepared in Example 2, it can be seen that Mo-NiCo PBA / NF catalyst has a smaller Tafel slope (15.59 mV dec -1 -1), indicating that it has faster reaction kinetics.

[0063] Figure 10 Chronoamperogram of Mo-NiCo PBA / NF electrocatalyst prepared in Example 2 in 1 mol / L KOH + 0.33 mol / L CO(NH2)2 mixed solution, it can be seen that Mo-NiCo PBA / NF electrocatalyst prepared in Example 2 has a current density of 10 mA cm -2The Mo-NiCo PBA / NF electrocatalyst prepared in Example 2 can be stably operated for more than 50 hours at a constant current density, and the voltage does not increase significantly, indicating that it has high stability in the electrocatalytic oxidation process.

[0064] Figure 11 The linear sweep voltammograms of the Mo-NiCo PBA / NF electrocatalyst prepared in Example 2 and commercial Pt / C / NF as anode and cathode, respectively, for a urea-assisted full water splitting electrolyzer in a mixed solution of 1 mol / L KOH + 0.33 mol / L CO(NH2)2 were prepared. The voltage of the electrolyzer composed of the Mo-NiCo PBA / NF electrocatalyst prepared in Example 2 and commercial Pt / C / NF was only 1.44 V at 50 mAcm -2 , which was 120 mV lower than that of the electrolyzer composed of commercial RuO2 / NF and commercial Pt / C / NF, indicating that the Mo-NiCo PBA / NF electrocatalyst prepared in Example 2 can be effectively used in the energy-saving hydrogen production of the urea-assisted electrolytic water system.

[0065] Figure 12 The chronoamperograms of the Mo-NiCo PBA / NF electrocatalyst prepared in Example 2 and commercial Pt / C / NF as anode and cathode, respectively, for a urea-assisted full water splitting electrolyzer can be seen that it can be stably operated for more than 27 hours at a constant current density of 10 mAcm -2 , and the voltage does not increase significantly, indicating that it has excellent stability in the urea-assisted full water splitting electrolyzer.

[0066] Example 3:

[0067] The Mo-NiCo PBA / NF electrocatalyst was prepared according to the method described in Example 2, and other conditions were kept unchanged, only the molar amount of Na2MoO4·2H2O was changed to 0.025 mmol.

[0068] Figure 13 The linear sweep voltammograms of the Mo-NiCo PBA / NF electrocatalyst prepared in Example 3 and commercial RuO2 / NF in a mixed solution of 1 mol / L KOH + 0.33 mol / L CO(NH2)2 can be seen from the figure that compared with commercial RuO2 / NF, the Mo-NiCo PBA / NF electrocatalyst has a lower initial potential, and only needs a voltage of 1.36 V to drive a large current density of 100 mAcm -2 , which is 160 mV lower than that of commercial RuO2 / NF, indicating that the Mo-NiCo PBA / NF electrocatalyst prepared in Example 3 has better urea oxidation performance.

[0069] Figure 14The image shows the Tafel curve of the Mo-NiCo PBA / NF electrocatalyst prepared in Example 3. It can be seen that the Mo-NiCo PBA / NF catalyst has a relatively small Tafel slope (18.79 mV dec). -1 This indicates that it has relatively fast reaction kinetics.

[0070] Example 4:

[0071] The Mo-NiCo PBA / NF electrocatalyst was prepared according to the method described in Example 2, keeping other conditions unchanged, except that the molar amount of Na2MoO4·2H2O was changed to 0.1 mmol.

[0072] Figure 15 The figure shows linear sweep voltammetry (SSW) voltammetry (LSW) plots of the Mo-NiCo PBA / NF electrocatalyst prepared in Example 4 and commercial RuO2 / NF in a mixed solution of 1 mol / L KOH + 0.33 mol / L CO(NH2)2. The plots show that the Mo-NiCo PBA / NF electrocatalyst has a lower onset potential than the commercial RuO2 / NF, with a driving potential of 100 mA / cm². -2 The high current density requires only 1.36V, which is 160mV lower than that of commercial RuO2 / NF, indicating that the Mo-NiCo PBA / NF electrocatalyst prepared in Example 4 has better urea oxidation performance.

[0073] Figure 16 The Tafel curve of the Mo-NiCo PBA / NF electrocatalyst prepared in Example 4 shows that the Mo-NiCo PBA / NF catalyst has a small Tafel slope (17.74 mV dec). -1 This indicates that it has relatively fast reaction kinetics.

[0074] Analyzing the above examples, the results of Examples 1, 2, 3, and 4 clearly demonstrate that molybdenum salt doping can effectively enhance the catalytic performance of the nickel-cobalt Prussian blue analogue urea oxidation reaction and improve its kinetic rate. Through the results of Examples 2, 3, and 4, we found that the amount of molybdenum salt doping affects the electro-oxidation performance of the nickel-cobalt Prussian blue analogue urea, with 0.05 mmol Na₂MoO₄·2H₂O being the optimal doping concentration. Example 2 exhibits the best catalytic performance, driving a 100 mA / cm² catalytic rate. -2 The voltage required for high current density is the lowest, and its Tafel slope is also the smallest.

Claims

1. A method for preparing a binary composite structure molybdenum-doped nickel-cobalt Prussian blue analog, characterized in that: a molybdenum-doped nickel-cobalt Prussian blue analog is prepared in situ on a foam nickel by a hydrothermal method, the foam nickel serving as both a nickel source and a conductive substrate; the structure of the molybdenum-doped nickel-cobalt Prussian blue analog is composed of a bottom plate structure and a surface-decorated rounded cube; and the method comprises the following steps: Step 1: placing a surfactant dextran-20, citric acid monohydrate, and a molybdenum salt in a beaker, dissolving them in deionized water to obtain solution A; Step 2: weighing K3[Co(CN)6] in a beaker, dissolving it in deionized water to obtain solution B; Step 3: adding solution A dropwise to solution B under stirring, and mixing well; and Step 4: transferring the mixed solution obtained in Step 3 into a Teflon-lined autoclave with pretreated foam nickel, and keeping it at 60-100°C for 10-14 hours; after the reaction is completed, the solution is naturally cooled to room temperature, washed with deionized water, and dried in an oven to obtain a binary composite structure molybdenum-doped nickel-cobalt Prussian blue analog Mo-NiCoPBA / NF.

2. The method according to claim 1, characterized in that: in Step 1, the molar amount of dextran-20 is 0.1 mmol, and the molar amount of citric acid monohydrate is 2.1 mmol.

3. The method according to claim 1, characterized in that: in Step 1, the molybdenum salt is Na2MoO4·2H2O, and the molar amount thereof is 0.01-0.1 mmol.

4. The method according to claim 1, characterized in that: in Step 2, the molar amount of K3[Co(CN)6] is 0.5 mmol.

5. The method according to claim 1, characterized in that: in Step 4, the pretreated foam nickel is obtained by the following method: cutting a foam nickel electrode, ultrasonically cleaning it with a dilute hydrochloric acid solution, acetone, and deionized water, and drying it in an oven for standby use.

6. Use of the binary composite structure molybdenum-doped nickel-cobalt Prussian blue analog prepared by the method according to any one of claims 1-5, characterized in that: the binary composite structure molybdenum-doped nickel-cobalt Prussian blue analog is used as a catalyst to realize an electrocatalytic oxidation reaction of urea under alkaline conditions.

7. The use according to claim 6, characterized in that: a three-electrode system is used, the molybdenum-doped nickel-cobalt Prussian blue analog is directly used as a working electrode, a platinum sheet electrode is used as a counter electrode, and a Hg / HgO electrode is used as a reference electrode, and the catalytic oxidation of urea is carried out in an alkaline electrolyte.

8. The use according to claim 7, 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.

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