Foamed nickel loaded nickel-cobalt bimetal organic framework electrocatalyst material, preparation method thereof and application of electrocatalyst material in urea oxidation reaction

Abstract

The invention relates to the technical field of electrocatalytic materials and new energy, in particular to a nickel foam loaded nickel-cobalt bimetal organic framework electrocatalyst material, a preparation method thereof and application in urea oxidation reaction, nickel salt, cobalt salt and organic ligand terephthalic acid are dissolved in a solvent, an NF substrate is added, the mixture is sealed in a reaction kettle, solvothermal reaction is performed, and the nickel foam loaded nickel-cobalt bimetal organic framework electrocatalyst material is obtained. After the reaction is finished, naturally cooling to room temperature, taking out a sample, cleaning with deionized water and absolute ethyl alcohol, and then drying to obtain a Ni-Co-BDC precursor; the Ni-Co-BDC precursor is soaked in an alkaline solution, and alkalization treatment is carried out at the room temperature; and after the treatment is finished, fully cleaning with deionized water, and then drying to obtain the final nickel-cobalt bimetallic electro-catalytic material. The Ni-Co-BDC bimetallic MOF is formed by introducing cobalt and nickel, double active sites are successfully constructed, the electronic structure of the nickel center is effectively adjusted, and the intrinsic activity of the catalyst is enhanced.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of electrocatalytic materials and new energy technology, in particular to a foam nickel supported nickel-cobalt bimetallic organic framework electrocatalyst material, a preparation method thereof and application thereof in urea oxidation reaction. BACKGROUND

[0002] Urea oxidation reaction is the core anode reaction of urea fuel cell, urea electrolysis hydrogen production and urea-containing wastewater treatment technology. Developing high-efficiency and stable UOR electrocatalyst is crucial for reducing the overpotential of the reaction and improving the energy conversion efficiency. At present, the best catalyst is still a noble metal-based material (such as Pt, IrO2), but its high cost and scarcity seriously limit its large-scale commercial application.

[0003] Nickel (Ni) based materials are widely studied because of their intrinsic electrocatalytic activity for UOR and low cost. However, the single nickel-based catalyst has limited active sites and poor electronic conductivity, resulting in unsatisfactory catalytic efficiency and stability. Studies have shown that introducing a second metal element (such as cobalt, Co) to form a bimetallic system with nickel can effectively adjust the electronic structure of the nickel center and produce a synergistic effect. Metal organic framework materials (MOFs) are ideal precursors for constructing such bimetallic catalysts due to their high specific surface area and adjustable metal sites. However, how to maximize the UOR electrocatalytic performance through a simple and controllable synthesis and post-processing path is still a technical problem to be solved in the field. SUMMARY

[0004] Based on the above-mentioned technical problems, the purpose of the present application is to overcome the shortcomings of the prior art, and to provide a foam nickel supported nickel-cobalt bimetallic organic framework electrocatalyst material, a preparation method thereof and application thereof in urea oxidation reaction, in order to develop an electrocatalyst with high catalytic activity and low cost, which can be used in the field of electrocatalytic urea oxidation reaction.

[0005] The present application is realized by the following technical scheme: a preparation method of a foam nickel supported nickel-cobalt bimetallic organic framework electrocatalyst material, comprising the following steps: S1, pretreating the foam nickel with dilute hydrochloric acid, deionized water and anhydrous ethanol in sequence, and then vacuum drying to remove the surface oxide layer and impurities; S2, precursor synthesis: dissolving nickel salt, cobalt salt and organic ligand terephthalic acid in a solvent, stirring uniformly, then adding the NF substrate, sealing in a reaction kettle, and performing solvent thermal reaction at a certain temperature for a certain time, after the reaction is completed, naturally cooling to room temperature, taking out the sample, washing with deionized water and anhydrous ethanol, and then drying to obtain a Ni-Co-BDC precursor; S3, alkali treatment: the obtained Ni-Co-BDC precursor is immersed in an alkaline solution, and alkali treatment is carried out at room temperature; after the treatment, the obtained Ni-Co-BDC precursor is washed with deionized water and dried to obtain the final nickel-cobalt bimetallic electrocatalytic material.

[0006] As a further improvement of the technical scheme of the application, the mass ratio of the nickel salt, the cobalt salt and the organic ligand terephthalic acid is 16:4:20.

[0007] As a further improvement of the technical scheme of the application, the solvent is a mixed solution of DMF, anhydrous ethanol and water, and the volume ratio is (4-6):(2-4):(1-3).

[0008] As a further improvement of the technical scheme of the application, the alkaline solution used in the alkali treatment is a KOH solution with a concentration of 2 mol / L -1 , and the treatment time is 0.5-1.5 h.

[0009] As a further improvement of the technical scheme of the application, the temperature of the solvothermal reaction is 90-150 ℃, and the reaction time is 6-18 h.

[0010] As a further improvement of the technical scheme of the application, the drying temperature for obtaining the Ni-Co-BDC precursor is 60-80 ℃, and the drying time is about 12 h.

[0011] The application also provides a preparation method of a foam nickel loaded nickel-cobalt bimetallic organic framework electrocatalyst material.

[0012] The application further provides an application of the nickel-cobalt bimetallic electrocatalytic material in electrocatalytic urea oxidation.

[0013] The application has the following advantages: (1) Bimetallic synergistic effect: by introducing cobalt and nickel to form a Ni-Co-BDC bimetallic MOF, a double active site is successfully constructed, the electronic structure of the nickel center is effectively adjusted, and the intrinsic activity of the catalyst is enhanced.

[0014] (2) Multi-parameter system optimization: the application optimizes key parameters such as solvent composition, nickel-cobalt ratio, solvothermal reaction temperature and time, and alkali treatment time, and realizes controllable and precise regulation of the structure and performance of the catalyst.

[0015] (3) Strengthening of post-treatment process: through alkali treatment, the MOF precursor is partially converted into metal (oxy) hydroxide with higher catalytic activity, and the structure advantage of the MOF is well retained, thereby further improving the electrocatalytic urea oxidation performance.

[0016] (4) Clear process window: By studying different combinations of temperature and time, the optimal process (120 ℃, 12 h) was identified, and a feasible preparation window was defined, providing a basis for large-scale production.

[0017] (5) Excellent overall performance: The prepared catalyst exhibits a low onset potential and high current density in the urea oxidation reaction, showing good catalytic activity.

[0018] (6) Cost and process advantages: The raw materials used are cheap and readily available, the synthesis method is simple and reproducible, and it is easy to scale up production. Attached Figure Description

[0019] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a scanning electron microscope image of the Ni-Co-BDC precursor prepared under optimal conditions according to an embodiment of the present invention.

[0022] Figure 2 This is a transmission electron microscope image of the Ni-Co-BDC precursor prepared under optimal conditions according to an embodiment of the present invention.

[0023] Figure 3 This is a cyclic voltammetry curve of the catalysts prepared under different solvent compositions for the precursors of this invention.

[0024] Figure 4 This is a cyclic voltammetry curve of the catalysts prepared under different nickel-cobalt ratios of the precursor prepared according to the present invention.

[0025] Figure 5 This is a cyclic voltammogram of the catalysts prepared at different solvothermal reaction temperatures for the precursors prepared in this invention.

[0026] Figure 6 This is a cyclic voltammogram of the catalysts prepared under different solvothermal reaction times for the precursors prepared in this invention.

[0027] Figure 7 This is a cyclic voltammogram of the catalysts prepared from the precursor of this invention under different alkalization treatment times. Detailed Implementation

[0028] In order to enable a more complete understanding of the above-mentioned objects, features and advantages of the present application, the following will further describe the solutions of the present application. It should be noted that the embodiments of the present application and the features in the embodiments can be combined with each other without conflict.

[0029] In the following description, a large number of specific details are set forth in order to facilitate a thorough understanding of the present application, but the present application can also be implemented in other manners different from those described herein; obviously, the embodiments described in the specification are only a part of the embodiments of the present application, and not all the embodiments.

[0030] The specific embodiments of the present application will be described in detail below.

[0031] The way of testing the catalyst UOR in the present application is as follows: The sample is used for the application of electrocatalytic urea oxidation decomposition. The electrochemical performance of the sample is tested by using an electrochemical workstation Gamry Interface 1000. A standard three-electrode test system is used, a platinum mesh (2 cm × 2 cm) is used as a counter electrode, an Ag / AgCl electrode is used as a reference electrode, and the prepared sample is used as a working electrode (the area immersed in the solution is 1 cm 2 ). The test solution used is a mixed solution of 1 M KOH and 0.33 M urea. The UOR performance of the catalyst is characterized by using cyclic voltammetry (CV). First, 150 cycles of circulation are carried out in a 1 M KOH solution at a scanning rate of 100 mV s -1 , and the catalyst is fully activated, and then 5 cycles of scanning are carried out in a mixed solution of 1 M KOH and urea at a scanning rate of 10 mV s -1 , and the UOR performance of the catalyst is tested.

[0032] In the specific embodiments of the present application, the pretreatment of the NF is carried out according to the following conventional steps: (1) ultrasonic cleaning of the NF with 3 M dilute hydrochloric acid for 15 min; (2) ultrasonic treatment of the NF with deionized water for 15 min, repeated three times; (3) ultrasonic treatment of the NF with anhydrous alcohol for 15 min; (4) drying under vacuum at 60 ℃ for 3 h.

[0033] Example 1: Preparation of Ni-Co-BDC precursor and optimization of solvent composition 40 mL of DMF was measured and placed in a beaker, and 40 mg of terephthalic acid was added and stirred to dissolve. Then, 16 mg of NiCl₂·6H₂O and 4 mg of CoCl₂·6H₂O were added, and the mixture was stirred at 25 °C for 15 min until completely dissolved. The mixture was transferred to a 100 mL reaction vessel, and a pretreated NF tablet was placed inside. The reaction vessel was sealed and placed in a forced-air drying oven, where it was reacted at 120 °C for 12 h. After the reaction was complete, the mixture was allowed to cool naturally, and the sample was removed, washed three times with distilled water, and dried in a 60 °C oven for 12 h to obtain the Ni-Co-BDC precursor. Keeping other conditions constant, only the solvent composition was changed, with the solvent ratios being DMF:anhydrous ethanol:water = 5:3:2, DMF:anhydrous ethanol = 1:1, and DMF:water = 1:1.

[0034] Example 2: Optimization of Nickel-Cobalt Mass Ratio Prepare a 40 mL mixture of DMF, anhydrous ethanol, and water in a ratio of 5:3:2. Keeping the total mass of nickel and cobalt salts constant at 20 mg, change the Ni:Co mass ratio to 10:10, 20:0, 18:2, and 16:4, while maintaining the same synthesis conditions as in Example 1 (120 °C, 12 h).

[0035] Example 3: Optimization of solvothermal reaction temperature and time Using DMF:anhydrous ethanol:water = 5:3:2 as solvent and adding nickel-cobalt salt with Ni:Co = 16:4, different reaction conditions were investigated: (1) Temperature series (fixed time 12 h): reaction at 90 ℃, 120 ℃, and 150 ℃ respectively; (2) Time series (fixed temperature 120 ℃): reaction at 6 h, 12 h, and 18 h respectively. UOR performance test showed that the sample reacted at 120 ℃ for 12 hours (T-12) had the best catalytic activity.

[0036] Example 4: Alkaliization Treatment. The optimal samples obtained in Examples 1, 2, and 3 were alkalized in a 2 mol / L KOH solution for 0.5 h, 1 h, and 1.5 h, respectively. After treatment, the samples were washed three times with deionized water and once with anhydrous ethanol, and then dried under vacuum at 60 °C for 12 h.

[0037] like Figure 1 As shown in the example, to investigate the effect of different solution compositions on the microstructure of the sample, we selected a sample with a nickel-cobalt ratio of 16:4 for SEM analysis, and obtained... Figure 1 .Depend on Figure 1 (a) It can be observed that the surface of the sample with DMF solution remains relatively smooth, and no obvious products adhere to the NF framework. Its microstructure is not significantly different from that of NF. Figure 1(b) It can be seen that the micro-morphology of the sample with solution composition of DMF: water = 1:1 changed greatly, and thicker flaky Ni-Co-BDC precursors were generated on the surface of the NF framework, which were regular in shape but uneven in growth. Figure 1 (c) It shows that the thickness of the flaky Ni-Co-BDC precursors generated on the surface of the sample with solution composition of DMF: anhydrous ethanol = 1:1 is greatly reduced, and the shape is irregular, and the growth is also uneven. Figure 1 (d) It shows that the thickness of the flaky Ni-Co-BDC precursors generated on the surface of the sample with solution composition of DMF: anhydrous ethanol: water = 5:3:2 is moderate, the shape is irregular, and the growth is more dense, and the growth is more uniform than the previous two solutions, but local peeling still occurs. It is thus inferred that anhydrous ethanol has the effect of reducing the thickness of Ni-Co-BDC precursors.

[0038] From Figure 2 (a) It can be seen that the Ni-Co-BDC precursors generated on the sample with solution composition of DMF: anhydrous ethanol: water = 5:3:2, Ni:Co = 16:4 are in a two-dimensional flaky structure, and the sample has weak crystallinity. Figure 2(b) is a TEM image of the sample with solution composition of DMF: anhydrous ethanol: water = 5:3:2, Ni:Co = 16:4 after 1h alkali treatment. It can be clearly observed that the surface of the sample becomes rough, and larger particles appear, indicating that the sample has Figure 2 (a) better crystallinity. It can be seen that alkali treatment helps to improve the specific surface area and roughness of the sample, change the crystallinity, and thus change the catalytic performance of the sample.

[0039] From Figure 3 It can be seen that when the current density is 10 mA cm -2 -1, the potential of the sample in UOR is DMF: water = 1:1 > DMF: anhydrous ethanol: water = 5:3:2 > DMF: anhydrous ethanol = 1:1, indicating that the increase of water makes the sample more easily meet the thermodynamic conditions of the reaction, and the electrochemical performance is better. For the samples with solution composition of DMF: water = 1:1 and DMF: anhydrous ethanol: water = 5:3:2, their electrocatalytic UOR performance is the best.

[0040] From Figure 4 It can be seen that for the sample with solution composition of DMF: anhydrous ethanol: water = 5:3:2, the addition of cobalt can significantly improve the UOR electrocatalytic performance of the sample, and the UOR electrocatalytic performance is the best when the ratio of nickel to cobalt is 16:4.

[0041] From Figure 5It can be seen that: when the solution composition is DMF: anhydrous ethanol: water = 5:3:2, and the nickel-cobalt ratio is 16:4, the effect of hydrothermal reaction temperature on the UOR electrocatalytic performance of the sample, when the hydrothermal temperature is 150℃, the performance is obviously reduced.

[0042] From Figure 6 It can be seen that: when the solution composition is DMF: anhydrous ethanol: water = 5:3:2, and the nickel-cobalt ratio is 16:4, the effect of hydrothermal reaction time on the UOR electrocatalytic performance of the sample, it can be seen that the sample obtained under the condition of 12h has the best UOR performance.

[0043] From Figure 7 It can be seen that: when the solution composition is DMF: anhydrous ethanol: water = 5:3:2, and the nickel-cobalt ratio is 16:4, the effect of hydrothermal reaction time on the UOR electrocatalytic performance of the sample, it can be seen that the sample obtained under the condition of 12h has the best UOR performance.

[0044] The above description is only a specific embodiment of the present application, which enables those skilled in the art to understand or implement the present application. Although the foregoing embodiments are described in detail, those skilled in the art should understand that the technical solutions recorded in the foregoing embodiments can be modified, or some or all of the technical features can be replaced by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments, and they should be covered in the protection scope of the claims.

Claims

1. A method for preparing a foamed nickel supported nickel-cobalt bi-metallic organic framework electrocatalyst material, characterized in that, The method comprises the following steps: S1, using dilute hydrochloric acid, deionized water, and anhydrous ethanol to sequentially pretreat the foamed nickel, and then vacuum drying to remove the surface oxide layer and impurities; S2, precursor synthesis: dissolving nickel salt, cobalt salt, and organic ligand terephthalic acid in a solvent, stirring uniformly, then adding the NF substrate, sealing in a reaction kettle, and performing a certain time of solvothermal reaction at a certain temperature, after the reaction, naturally cooling to room temperature, taking out the sample, washing with deionized water and anhydrous ethanol, and then drying to obtain the Ni-Co-BDC precursor; S3, alkalization treatment: immersing the obtained Ni-Co-BDC precursor in an alkaline solution, performing alkalization treatment at room temperature, after the treatment, washing with deionized water, and then drying to obtain the final nickel-cobalt bimetallic electrocatalytic material.

2. The method of claim 1, wherein the method is characterized by: The mass ratio of the nickel salt, the cobalt salt, and the organic ligand terephthalic acid is 16:4:

20.

3. The method of claim 1, wherein the method is characterized by: The solvent is a mixed solution of DMF, anhydrous ethanol, and water, and the volume ratio is (4-6):(2-4):(1-3).

4. The method of claim 1, wherein the method is characterized by: The alkaline solution used in the alkalization treatment is a KOH solution with a concentration of 2 mol L -1 and a treatment time of 0.5-1.5 h.

5. The method of claim 1, wherein the method is characterized by: The temperature of the solvothermal reaction is 90-150 ℃, and the reaction time is 6-18 h.

6. The method of claim 1, wherein the method is characterized by: The drying temperature for obtaining the Ni-Co-BDC precursor is 60-80 ℃, and the drying time is about 12 h.

7. The nickel-cobalt bimetallic electrocatalytic material prepared by the preparation method of the foamed nickel loaded nickel-cobalt bimetallic organic framework electrocatalyst material according to any one of claims 1 to 6.

8. The application of the nickel-cobalt bimetallic electrocatalytic material according to claim 7 in electrocatalytic urea oxidation.

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