Preparation method of ni-mn bimetallic electrocatalyst and small molecule electro-oxidation application thereof

Abstract

The application relates to a preparation method of a Ni-Mn bimetallic electrocatalyst and application of the electrocatalyst in small molecule electrooxidation, and belongs to the field of electrocatalysis. The method comprises the following steps: cleaning a substrate to remove a surface oxide layer; dissolving nickel salt, manganese salt, terephthalic acid, salicylic acid and urea into a mixed solution of ethanol, DMF and water, and transferring the mixed solution and the treated substrate into a hydrothermal kettle to perform a hydrothermal reaction; and after cooling, cleaning and drying, a NiMn-MOF / NF catalyst precursor is obtained. Sodium borohydride and selenium powder are dissolved and stirred, and are transferred into the hydrothermal kettle to perform a hydrothermal selenization reaction with the NiMn-MOF / NF; and after cooling and cleaning, a self-supporting NiMn-MOF-Se / NF catalyst with a uniform nanosheet structure is obtained. The catalyst synthesis method is simple and controllable, the cost is low, the catalyst morphology is uniform, the conductivity is good, the catalyst can be directly used as an electrode, and the catalyst exhibits excellent catalytic activity in the electrocatalytic oxidation of small molecules such as methanol and ethylene glycol, and has a wide application prospect.

Description

Technical Field

[0001] This invention belongs to the field of electrocatalysis, specifically relating to a method for preparing a Ni / Mn bimetallic electrocatalyst and its small molecule electro-oxidation application. Background Technology

[0002] With the development of clean and renewable energy sources such as wind and solar power, electro-driven catalytic small molecule conversion has ushered in new development opportunities, especially water electrolysis for hydrogen production and electrochemical synthesis of fine chemicals. The depletion of fossil fuel reserves and the resulting environmental pollution have fueled the robust development of hydrogen energy as a green and clean energy source. With the maturation of technology and large-scale development, the use of hydrogen energy is expected to achieve low carbon emissions throughout its entire life cycle, contributing to the achievement of dual-carbon goals.

[0003] Hydrogen production through water electrolysis is constrained by energy consumption, putting it at a cost disadvantage compared to hydrogen production from fossil fuels. Reducing energy consumption is crucial for its large-scale application. The oxygen evolution reaction (OER) at the anode accounts for over 90% of the energy consumption in hydrogen production through water electrolysis, and the resulting oxygen has low economic value, representing a significant bottleneck that urgently needs to be addressed. Small molecule oxidation reactions, as an alternative to OER, offer an effective strategy for reducing energy consumption in water electrolysis. Small molecule alcohols, such as methanol and glycerol, have lower oxidation potentials than OER, resulting in significant energy savings at the same hydrogen production rate. Furthermore, the electrochemical upgrading of small molecule chemicals can increase added value, thereby reducing the overall cost of the hydrogen production process. Additionally, it effectively avoids contact between hydrogen and oxygen in traditional water electrolysis, improving the safety and operating cycle of the equipment.

[0004] Developing catalysts with high catalytic activity, high product selectivity, good stability, and low cost is crucial for the electrocatalytic oxidation of small organic molecules coupled with hydrogen production, and is also an important way to reduce the cost of hydrogen production through water electrolysis. CN114086202A discloses a non-precious metal catalyst for glycerol oxidation-assisted hydrogen production, using Co3O4 material grown on nickel foam obtained through a hydrothermal method and high-temperature calcination. This catalyst achieves 10 mA / cm² at 1.22 V. 2 The above studies show that many of the currently disclosed catalysts have problems such as low catalytic activity and poor selectivity. In particular, the catalytic activity and stability under industrial current density requirements are difficult to meet actual needs. At the same time, most catalysts are difficult to prepare on a large scale. Therefore, it is of great significance to develop low-cost catalysts with high activity and high selectivity for the electro-oxidation of small molecules. Summary of the Invention

[0005] To overcome the shortcomings of existing technologies, this invention provides a method for preparing Ni / Mn bimetallic electrocatalysts and their small molecule electro-oxidation applications. It has advantages such as simple and controllable synthesis process, low raw material cost, high catalytic activity and selectivity, and scalable preparation, and is expected to provide excellent catalysts for the industrial development of electrocatalytic small molecule oxidation coupled with green hydrogen production.

[0006] To achieve the above-mentioned objectives and solve the problems existing in the prior art, the technical solution adopted by the present invention is as follows:

[0007] A method for preparing a Ni / Mn bimetallic electrocatalyst includes the following steps:

[0008] (1) Clean the substrate to remove the surface oxide layer and obtain the treated substrate;

[0009] (2) Dissolve nickel salt, manganese salt, terephthalic acid, salicylic acid and urea into a mixed solution, and transfer it together with the treated matrix into a high-pressure hydrothermal reactor for hydrothermal reaction; then cool, clean and dry to obtain NiMn-MOF precursor;

[0010] The molar ratio of nickel salt to manganese salt is 0.5:1 to 2:1, and the molar ratio of terephthalic acid to metal salt is 1:8 to 1:2; the mixed solution is a mixture of ethanol, N,N-dimethylformamide and water.

[0011] (3) Dissolve sodium borohydride and selenium powder in deionized water and stir continuously for 0.5-2 h under a nitrogen atmosphere; then transfer to a high-pressure hydrothermal reactor and add NiMn-MOF precursor to carry out hydrothermal selenization reaction; then cool and wash to obtain a self-supporting NiMn-MOF-Se catalyst with uniform nanosheet structure; the mass ratio of sodium borohydride to selenium powder is 1:1 to 1:4.

[0012] The substrate is nickel foam, copper foam, or carbon fiber paper; nickel foam substrate is preferred.

[0013] Step (1) Clean the substrate by sequentially cleaning it with hydrochloric acid, ethanol and water.

[0014] The volume ratio of ethanol, N,N-dimethylformamide, and water in the mixture is 1:3:2.

[0015] In step (2), the hydrothermal reaction temperature is 120-160℃ and the reaction time is 6-24h.

[0016] In step (3), the temperature of the hydrothermal selenization reaction is 120-160℃ and the reaction time is 6-24h.

[0017] The nickel salt is nickel nitrate, nickel acetate, nickel chloride, or nickel sulfate; the manganese salt is manganese sulfate, manganese nitrate, or manganese chloride.

[0018] The NiMn-MOF-Se catalyst is used for the electrochemical oxidation of small molecule alcohols.

[0019] The NiMn-MOF-Se catalyst is used for the electrochemical oxidation of methanol, ethylene glycol, or glycerol.

[0020] Commercially available nickel foam substrates can be replaced with copper foam or carbon fiber paper.

[0021] The ratio of ethanol, N,N-dimethylformamide, and water is 1:3:2 to ensure the complete dissolution of terephthalic acid.

[0022] The ratio of sodium borohydride to selenium powder is 1:1 to 1:4. When stirring under a nitrogen atmosphere, it is necessary to wait for the selenium powder and sodium borohydride to react fully and for the solution to become clear.

[0023] The prepared Ni / Mn bimetallic electrocatalyst can be applied to the electrochemical oxidation of small molecule chemicals such as methanol, ethylene glycol, and glycerol.

[0024] Further, the specific steps are as follows:

[0025] Step 1) Cut the nickel foam substrate into 2*4cm pieces. 2 The sample was ultrasonically cleaned with 1-3 mol / L hydrochloric acid for 30 minutes, and then repeatedly cleaned with ethanol and water.

[0026] Step 2) Dissolve 1 mmol Ni(NO3)2·6H2O, 1 mmol MnCl2·4H2O, 0.5 mmol terephthalic acid, 0.2 g salicylic acid, and 0.3 g urea in a mixed solution of ethanol, N,N-dimethylformamide, and water using ultrasonication. Transfer this solution, along with the treated nickel foam, to a hydrothermal reactor and maintain the solution at 150 °C for 12 h. After cooling, wash with deionized water and ethanol, and dry overnight in an oven at 60 °C to obtain the NiMn-MOF / NF catalyst precursor.

[0027] Step 3) Weigh 0.1g sodium borohydride and 0.16g selenium powder and dissolve them in deionized water. Stir continuously for 30min under a nitrogen atmosphere. After the solution starts to change from black to colorless, transfer it to a hydrothermal reactor and add the NiMn-MOF / NF catalyst precursor obtained in Step 2. Perform hydrothermal selenization reaction and maintain at 140℃ for 8h. After cooling, wash with deionized water and ethanol, and dry in an oven at 60℃ overnight to obtain a self-supported NiMn-MOF-Se / NF catalyst with a uniform nanosheet structure.

[0028] Electrocatalytic small molecule oxidation performance study. In a standard three-electrode electrolytic cell system, the NiMn-MOF-Se / NF catalyst was directly used as the working electrode, and Hg / HgO and a carbon rod were used as the reference electrode and counter electrode, respectively. The electrolyte consisted of 1M KOH with an appropriate concentration of organic small molecule substrate (e.g., 0.5 mol / L methanol). All electrochemical performance tests were performed using a Chenhua 760E electrochemical workstation. Before the tests, CV electrochemical activation was performed, with the voltage range set to -0.2 to 0.6 V (vs. Hg / HgO), the scan rate to 10 mV / s, and the number of scan cycles to 40. After the CV scan curve stabilized, the LSV polarization curve was tested, with the following parameters: potential range -0.2 V to 0.6 V (vs. Hg / HgO), scan rate to 10 mV / s, and iR compensation set to 85%. In addition to polarization curves, quantitative analysis of the Faraday efficiency of oxidation products is required. Electrolytes operating at different voltages for 2 hours were obtained using the transverse potential method. 1 Quantitative analysis was performed using 1H NMR. The Faraday efficiency of the target product was calculated based on the amount of transferred charge. Finally, multiple charge-time curves were obtained using the potentiostatic method to evaluate the stability of the catalyst.

[0029] The advantages of this invention are: the preparation method is simple and controllable, the raw materials are non-precious metals, the cost is low, it can be prepared on a large scale, and the uniformity of the catalyst morphology is easy to achieve. In terms of applications, the synthesized NiMn-MOF-Se catalyst exhibits excellent catalytic activity for small molecule alcohols (methanol, glycerol, ethylene glycol, etc.), thus demonstrating significant energy-saving potential in the coupled hydrogen production industry, and enabling the conversion of low-value chemicals into high-value-added chemicals.

[0030] The introduction of high-valence metals and hybridization with non-metallic elements facilitates the modulation of the electronic structure of the active center, thereby enhancing catalytic activity and selectivity. Furthermore, as a self-supporting electrode, it eliminates the need for adhesives, resulting in excellent electron transport capabilities and low interfacial resistance. The abundant pore structure and good hydrophilicity provided by the nanoarray also promote the exposure of active sites and electrolyte penetration. The NiMn-MOF-Se / NF catalyst synthesized in this invention exhibits excellent catalytic activity and selectivity for the electro-oxidation of small molecules such as methanol, achieving 400 mA cm⁻¹ oxidation at only 1.42 V (vs. RHE). -2 With an industrial current density and a formic acid product selectivity of over 95%, it can meet the needs of commercialization and provides a reliable catalyst for the development of electrochemical synthesis coupled with green hydrogen preparation systems. Attached Figure Description

[0031] Figure 1 This is a SEM image of the NiMn-MOF-Se / NF catalyst in Example 1.

[0032] Figure 2 This is the XRD pattern of the NiMn-MOF-Se / NF catalyst in Example 1.

[0033] Figure 3 This is an LSV curve of methanol electro-oxidation using precursors with different proportions of Ni and Mn in Example 3.

[0034] Figure 4 This is the LSV curve of methanol electro-oxidation by the NiMn-MOF-Se / NF catalyst in Example 9. Detailed Implementation

[0035] The present invention will be further described below with reference to embodiments. The following non-limiting embodiments are intended to enable those skilled in the art to more fully understand the present invention, but do not limit the present invention in any way.

[0036] Unless otherwise specified, the experimental methods described in the following examples are conventional methods; unless otherwise specified, the reagents and materials are commercially available.

[0037] Example 1

[0038] The preparation method of Ni / Mn bimetallic electrocatalysts for small molecule electrooxidation is as follows:

[0039] Step 1) Cut the nickel foam substrate into 2*4cm pieces. 2 The sample was ultrasonically cleaned with 2 mol / L hydrochloric acid for 30 min, and then repeatedly rinsed with ethanol and water to remove the surface oxide layer.

[0040] Step 2) Dissolve 1 mmol Ni(NO3)2·6H2O, 1 mmol MnCl2·4H2O, 0.5 mmol terephthalic acid, 0.2 g salicylic acid, and 0.3 g urea in a mixed solution containing 5 mL ethanol, 15 mL N,N-dimethylformamide, and 10 mL water using ultrasonication. Transfer this solution, along with the treated nickel foam matrix, to an autoclave and maintain the solution at 150 °C for 12 h. After cooling, wash the nickel foam with the grown nanocatalyst using deionized water and ethanol, and dry it overnight in an oven to obtain the NiMn-MOF / NF precursor catalyst.

[0041] Step 3) Weigh 0.1g sodium borohydride and 0.2g selenium powder and dissolve them in deionized water. Stir continuously for 30min under a nitrogen atmosphere. After the solution starts to change from black to colorless, transfer it to a high-pressure hydrothermal reactor. At the same time, add the NiMn-MOF / NF precursor obtained in step 2 and carry out a hydrothermal selenization reaction at 140℃ for 8h. After cooling, wash and dry overnight to obtain a self-supporting NiMn-MOF-Se / NF catalyst with a uniform nanosheet structure.

[0042] The material morphology was characterized by scanning electron microscopy, and the results showed that the NiMn-MOF-Se / NF catalyst had a uniform nanosheet structure grown on a nickel foam matrix framework. Figure 1 Subsequently, its crystal structure was characterized by XRD. Figure 2 Its characteristic peaks are similar to those of NiSe (PDF:18-0887) on the (300), (021), (211), (131), (103), and (201) crystal planes and Ni 0.85 The (101), (102), and (110) crystal planes of Se (PDF:18-0888) are matched, where Mn is incorporated into the NiSe crystal structure in a lattice-doped manner.

[0043] Example 2

[0044] The preparation method of Ni / Mn bimetallic electrocatalysts for small molecule electrooxidation mentions the use of replaceable substrates, which can also achieve good results. Here, copper foam and carbon paper are selected as the research substrates, as follows:

[0045] Step 1) Cut the foam copper and carbon paper into 2*4cm pieces. 2 The sample was ultrasonically cleaned with 2 mol / L hydrochloric acid for 30 min, and then rinsed repeatedly with ethanol and water.

[0046] Step 2) Dissolve 1 mmol Ni(NO3)2·6H2O, 1 mmol MnCl2·4H2O, 0.5 mmol terephthalic acid, 0.2 g salicylic acid, and 0.3 g urea in a mixed solution containing 5 mL ethanol, 15 mL N,N-dimethylformamide, and 10 mL water using ultrasonication. Transfer this solution, along with treated copper foam or carbon paper, to an autoclave and maintain the solution at 150 °C for 12 h. After cooling, clean and dry to obtain the NiMn-MOF / CF precursor catalyst.

[0047] Step 3) Weigh 0.1g sodium borohydride and 0.16g selenium powder and dissolve them in deionized water. After stirring continuously for 30 minutes under a nitrogen atmosphere, transfer the mixture to a high-pressure hydrothermal reactor and add the NiMn-MOF / CF precursor obtained in Step 2. Perform a hydrothermal selenization reaction at 140℃ for 8 hours. After cooling, clean and dry the mixture and dry it overnight in an oven at 60℃ to obtain the self-supporting NiMn-MOF-Se / CF catalyst.

[0048] From a morphological perspective, replacing the substrate with carbon fiber paper or copper foam has minimal impact on the catalyst morphology, which still exhibits a uniform nanoarray structure. Further electrochemical tests using the same method were conducted to evaluate the catalytic performance of both catalysts. Compared to the nickel foam substrate, the performance of both catalysts decreased. The copper foam substrate catalyst performed relatively well, slightly inferior to the NiMn-MOF-Se / NF catalyst. However, the performance of the carbon paper substrate catalyst was significantly reduced due to the inherent conductivity and charge transfer capacity of the carbon paper, requiring an anode potential of 1.5V–1.6V (vs. RHE) to achieve 400 mA cm⁻¹. -2 Industrial current density.

[0049] Example 3

[0050] The preparation method of Ni / Mn bimetallic electrocatalysts for small molecule electrooxidation mentions that the ratio of Ni to Mn precursors can be adjusted. Further investigation is needed:

[0051] Step 1) Cut the nickel foam substrate into 2*4cm pieces. 2 The sample was ultrasonically cleaned with 2 mol / L hydrochloric acid for 30 min, and then rinsed with ethanol and water.

[0052] Step 2) Dissolve 1 mmol Ni(NO3)2·6H2O, 1 mmol MnCl2·4H2O, 0.5 mmol terephthalic acid, 0.2 g salicylic acid, and 0.3 g urea in a mixed solution containing 5 mL ethanol, 15 mL N,N-dimethylformamide, and 10 mL water using ultrasonication. Prepare two additional solutions with different Ni and Mn ratios: one containing 2 mmol Ni(NO3)2·6H2O and 1 mmol MnCl2·4H2O, and the other containing 1 mmol Ni(NO3)2·6H2O and 2 mmol MnCl2·4H2O. The amounts of other chemicals added are the same. After thorough stirring and dissolution, transfer the solutions together with the treated nickel foam matrix to an autoclave and maintain at 150 °C for 12 h. After cooling, clean and dry to obtain three catalysts: Ni1Mn2-MOF / NF, Ni1Mn1-MOF / NF, and Ni2Mn1-MOF / NF.

[0053] In a standard three-electrode electrolyzer system, the three catalysts mentioned above were used directly as working electrodes, with Hg / HgO and carbon rods serving as reference and counter electrodes, respectively. The electrolyte consisted of 1 mol / L KOH and 0.5 mol / L methanol. All electrochemical performance tests were conducted using a Chenhua 760E electrochemical workstation. The results showed that the three precursor catalysts exhibited different catalytic activities for methanol oxidation, with Ni1Mn1-MOF / NF exhibiting the best catalytic performance, requiring only an electrode potential of 1.42 V (vs. RHE) to achieve 400 mA cm⁻¹. -2 Industrial current density ( Figure 3 The other two require 1.48V and 1.53V respectively.

[0054] Example 4

[0055] The preparation method of Ni / Mn bimetallic electrocatalysts for small molecule electrooxidation mentions a molar ratio of terephthalic acid to metal precursor of 1:8 to 1:2. Further investigation is needed:

[0056] Step 1) Cut the nickel foam substrate into 2*4cm pieces. 2 The sample was ultrasonically cleaned with 2 mol / L hydrochloric acid for 30 min, and then rinsed with ethanol and water.

[0057] Step 2) Dissolve 1 mmol Ni(NO3)2·6H2O, 1 mmol MnCl2·4H2O, 0.5 mmol terephthalic acid, 0.2 g salicylic acid, and 0.3 g urea in a mixed solution containing 5 mL ethanol, 15 mL N,N-dimethylformamide, and 10 mL water using ultrasonication. Prepare two separate mixed solutions containing 0.25 mmol and 1 mmol terephthalic acid, respectively. Transfer these solutions, along with the treated nickel foam matrix, to an autoclave and maintain at 150 °C for 12 h. After cooling, clean and dry to obtain NiMn-MOF / NF precursor catalysts with different terephthalic acid contents.

[0058] Step 3) Weigh 0.1g sodium borohydride and 0.16g selenium powder and dissolve them in deionized water. After stirring continuously for 30 minutes under a nitrogen atmosphere, transfer the mixture to a high-pressure hydrothermal reactor. At the same time, add the three NiMn-MOF / NF precursors obtained in Step 2 and carry out a hydrothermal selenization reaction at 140℃ for 8 hours. After cooling, wash and dry overnight to obtain the self-supported NiMn-MOF-Se / NF catalyst.

[0059] During the dissolution process of the mixture in step 2, it was found that the prepared mixed solution had limited solubility for terephthalic acid. Excess terephthalic acid was difficult to dissolve completely. According to the scanning electron microscope results, the morphology of the catalyst was slightly different, but not very obvious. Therefore, the ratio of terephthalic acid to metal precursor added is 1:4, which is most suitable.

[0060] Example 5

[0061] The preparation method of Ni / Mn bimetallic electrocatalysts for small molecule electrooxidation mentions that the hydrothermal reaction temperature in step 2 is 120–160 °C. Further investigation is needed:

[0062] Step 1) Cut the nickel foam substrate into 2*4cm pieces. 2 The sample was ultrasonically cleaned with 2 mol / L hydrochloric acid for 30 min, and then rinsed with ethanol and water to remove the surface oxide layer.

[0063] Step 2) Dissolve 1 mmol Ni(NO3)2·6H2O, 1 mmol MnCl2·4H2O, 0.5 mmol terephthalic acid, 0.2 g salicylic acid, and 0.3 g urea in a mixed solution containing 5 mL ethanol, 15 mL N,N-dimethylformamide, and 10 mL water using ultrasonication. Transfer this solution, along with the treated nickel foam matrix, to an autoclave and maintain the solutions at 120 °C, 130 °C, 140 °C, 150 °C, and 160 °C for 12 h, respectively. After cooling, clean and dry to obtain the NiMn-MOF / NF precursor catalyst.

[0064] Step 3) Weigh 0.1g sodium borohydride and 0.16g selenium powder and dissolve them in deionized water. After stirring continuously for 30 minutes under a nitrogen atmosphere, transfer the mixture to a high-pressure hydrothermal reactor. At the same time, add the three NiMn-MOF / NF precursors obtained in Step 2 and carry out a hydrothermal selenization reaction at 140℃ for 8 hours. After cooling, wash and dry overnight to obtain the self-supported NiMn-MOF-Se / NF catalyst.

[0065] In terms of morphology, the temperature of the hydrothermal reaction in step 2 affects the synthesis of the catalyst. As the reaction temperature increases, the structure of the nanoarray becomes more uniform. There is little difference between the three temperatures of 140℃, 150℃ and 160℃. In terms of catalytic activity, the catalysts synthesized at each temperature all exhibit excellent catalytic performance, especially at the temperatures of 150℃ and 160℃, where the performance is the best.

[0066] Example 6

[0067] The preparation method of Ni / Mn bimetallic electrocatalysts for small molecule electrooxidation mentions that the hydrothermal reaction time in step 2 is 6–24 h. This paper investigates the relevant findings.

[0068] Step 1) Cut the nickel foam substrate into 2*4cm pieces. 2 The sample was ultrasonically cleaned with 2 mol / L hydrochloric acid for 30 min, and then rinsed with ethanol and water.

[0069] Step 2) Dissolve 1 mmol Ni(NO3)2·6H2O, 1 mmol MnCl2·4H2O, 0.5 mmol terephthalic acid, 0.2 g salicylic acid, and 0.3 g urea in a mixed solution containing 5 mL ethanol, 15 mL N,N-dimethylformamide, and 10 mL water using ultrasonication. Transfer this solution, along with the treated nickel foam matrix, to an autoclave and maintain the solution at 120 °C for 6 h, 8 h, 12 h, 18 h, and 24 h, respectively. After cooling, clean and dry to obtain the NiMn-MOF / NF precursor catalyst.

[0070] Step 3) Weigh 0.1g sodium borohydride and 0.16g selenium powder and dissolve them in deionized water. After stirring continuously for 30 minutes under a nitrogen atmosphere, transfer the mixture to a high-pressure hydrothermal reactor. At the same time, add the three NiMn-MOF / NF precursors obtained in Step 2 and carry out a hydrothermal selenization reaction at 140℃ for 8 hours. After cooling, wash and dry overnight to obtain the self-supported NiMn-MOF-Se / NF catalyst.

[0071] In terms of morphology, the hydrothermal reaction time in step 2 has little effect on the catalyst, but in terms of catalytic activity, the catalysts prepared at 8h and 12h can already exhibit the desired catalytic performance.

[0072] Example 7

[0073] The preparation method of Ni / Mn bimetallic electrocatalysts for small molecule electrooxidation mentions that the ratio of sodium borohydride to selenium powder in step 3 is 1:1 to 1:4. Further investigation is needed:

[0074] Step 1) Cut the nickel foam substrate into 2*4cm pieces. 2 The sample was ultrasonically cleaned with 2 mol / L hydrochloric acid for 30 min, and then rinsed with ethanol and water.

[0075] Step 2) Dissolve 1 mmol Ni(NO3)2·6H2O, 1 mmol MnCl2·4H2O, 0.5 mmol terephthalic acid, 0.2 g salicylic acid, and 0.3 g urea in a mixed solution containing 5 mL ethanol, 15 mL N,N-dimethylformamide, and 10 mL water using ultrasonication. Transfer this solution, along with the treated nickel foam matrix, to an autoclave and maintain the solution at 120 °C for 12 h. After cooling, clean and dry to obtain the NiMn-MOF / NF precursor catalyst.

[0076] Step 3) Weigh out different proportions of sodium borohydride and selenium powder (Sample 1: 1.0g sodium borohydride and 1.0g selenium powder; Sample 2: 1.0g sodium borohydride and 2.0g selenium powder; Sample 3: 1.0g sodium borohydride and 3.0g selenium powder; Sample 4: 1.0g sodium borohydride and 4.0g selenium powder) and dissolve them in deionized water. Stir continuously under a nitrogen atmosphere until the solution becomes clear, then transfer it to a high-pressure hydrothermal reactor. At the same time, add the three NiMn-MOF / NF precursors obtained in Step 2 and carry out a hydrothermal selenization reaction at 140℃ for 8 hours. After cooling, wash and dry overnight to obtain the self-supported NiMn-MOF-Se / NF catalyst.

[0077] Studies have found that the content of sodium borohydride and selenium powder determines the progress of their reaction. When the selenium powder content is low, excessive sodium borohydride will cause the reduction of metals in the catalyst, which will affect the morphology and performance. Excess selenium powder will be difficult to clarify during stirring, but it will not affect the morphology and performance of the material, resulting in a waste of resources.

[0078] Example 8

[0079] The preparation method of Ni / Mn bimetallic electrocatalysts for small molecule electrooxidation mentions that the hydrothermal temperature in step 3 is 120–160℃ and the reaction time is 6–24 h. Further investigation is needed:

[0080] Step 1) Cut the nickel foam substrate into 2*4cm pieces. 2 The sample was ultrasonically cleaned with 2 mol / L hydrochloric acid for 30 min, and then rinsed with ethanol and water.

[0081] Step 2) Dissolve 1 mmol Ni(NO3)2·6H2O, 1 mmol MnCl2·4H2O, 0.5 mmol terephthalic acid, 0.2 g salicylic acid, and 0.3 g urea in a mixed solution containing 5 mL ethanol, 15 mL N,N-dimethylformamide, and 10 mL water using ultrasonication. Transfer this solution, along with the treated nickel foam matrix, to an autoclave and maintain the solution at 120 °C for 12 h. After cooling, clean and dry to obtain the NiMn-MOF / NF precursor catalyst.

[0082] Step 3) Weigh 0.1g sodium borohydride and 0.2g selenium powder and dissolve them in deionized water. After stirring continuously for 30 minutes under a nitrogen atmosphere, transfer the mixture to a high-pressure hydrothermal reactor. At the same time, add the three NiMn-MOF / NF precursors obtained in Step 2 and carry out hydrothermal selenization reaction. Maintain the reaction at 140℃, 150℃ and 160℃ for 6h, 12h, 18h and 24h respectively. After cooling, wash and dry overnight to obtain the self-supported NiMn-MOF-Se / NF catalyst.

[0083] The results show that the hydrothermal reaction time and reaction temperature in step 3 have little effect on the catalyst, especially the reaction time. However, in terms of catalytic activity, increasing the reaction temperature is beneficial to the selenization process, and thus the catalytic activity is also improved.

[0084] Example 9

[0085] The preparation method of Ni / Mn bimetallic electrocatalysts for small molecule electrooxidation mentions that the catalyst can be used for the electrochemical oxidation of small molecule chemicals such as methanol, ethylene glycol, and glycerol. Further research is needed.

[0086] The NiMn-MOF-Se / NF catalyst was prepared using the method described in Example 1. Electrochemical performance tests were then conducted under the same electrolysis conditions and apparatus, with the exception that methanol in the electrolyte was replaced with 0.5 mol / L ethylene glycol and 0.5 mol / L glycerol. Based on the polarization curves, the NiMn-MOF-Se / NF catalyst exhibits broad applicability for the electrochemical oxidation of various small molecules, demonstrating excellent catalytic activity. Achieving 400 mA / cm² can be achieved with electrode potentials of only 1.39 V and 1.40 V (vs. RHE). -2 Industrial current density ( Figure 4 Furthermore, the electrolysis products are all formic acid, and the Faraday efficiency exceeds 90%.

[0087] The method for preparing a Ni / Mn bimetallic electrocatalyst disclosed in this invention is simple and controllable, has low cost due to its non-precious metal nature, and can be prepared on a large scale according to demand. In addition, it also exhibits attractive catalytic activity and selectivity, and has broad application prospects, with important economic and practical value.

[0088] Although the invention has been specifically shown and described by reference to the embodiments, it should be understood by those skilled in the art that various changes in form and detail, and various combinations of embodiments, may be made therein without departing from the spirit and scope of the invention as defined by the claims.

Claims

1. A method for preparing a Ni / Mn bimetallic electrocatalyst, characterized in that: Includes the following steps: (1) Clean the substrate to remove the surface oxide layer and obtain the treated substrate; (2) Dissolve nickel salt, manganese salt, terephthalic acid, salicylic acid and urea into a mixed solution, and transfer it together with the treated matrix into a high-pressure hydrothermal reactor for hydrothermal reaction; then cool, clean and dry to obtain NiMn-MOF precursor; The molar ratio of nickel salt to manganese salt is 0.5:1 to 2:1, and the molar ratio of terephthalic acid to the total molar ratio of nickel salt and manganese salt is 1:8 to 1:2; the mixed solution is a mixture of ethanol, N,N-dimethylformamide and water. (3) Dissolve sodium borohydride and selenium powder in deionized water and stir continuously for 0.5-2 h under a nitrogen atmosphere; then transfer to a high-pressure hydrothermal reactor and add NiMn-MOF precursor to carry out hydrothermal selenization reaction; then cool and wash to obtain a self-supporting NiMn-MOF-Se catalyst with uniform nanosheet structure; the mass ratio of sodium borohydride and selenium powder is 1:1 to 1:

4.

2. The method for preparing a Ni / Mn bimetallic electrocatalyst according to claim 1, characterized in that: The substrate is nickel foam, copper foam, or carbon fiber paper.

3. The method for preparing a Ni / Mn bimetallic electrocatalyst according to claim 2, characterized in that: The substrate is a nickel foam substrate.

4. The method for preparing a Ni / Mn bimetallic electrocatalyst according to claim 1, characterized in that: Step (1) Clean the substrate by sequentially cleaning it with hydrochloric acid, ethanol and water.

5. The method for preparing a Ni, Mn bimetallic electrocatalyst according to claim 1, characterized in that: The volume ratio of ethanol, N,N-dimethylformamide and water in the mixture is 1:3:

2.

6. The method for preparing a Ni, Mn bimetallic electrocatalyst according to claim 1, characterized in that: In step (2), the hydrothermal reaction temperature is 120~160 ℃ and the reaction time is 6~24 h.

7. The method for preparing a Ni, Mn bimetallic electrocatalyst according to claim 1, characterized in that: In step (3), the temperature of the hydrothermal selenization reaction is 120~160℃ and the reaction time is 6~24 h.

8. The method for preparing a Ni, Mn bimetallic electrocatalyst according to claim 1, characterized in that: The nickel salt is nickel nitrate, nickel acetate, nickel chloride, or nickel sulfate; the manganese salt is manganese sulfate, manganese nitrate, or manganese chloride.

9. The application of the NiMn-MOF-Se catalyst prepared by any one of claims 1-8 in the electrochemical oxidation of small molecule alcohols, wherein the small molecule alcohol is methanol, ethylene glycol or glycerol.

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