Hydrogen evolution reaction electrocatalyst, preparation method and application thereof

Abstract

The present application relates to the field of hydrogen evolution reaction electrocatalyst, discloses hydrogen evolution reaction electrocatalyst and its preparation method and application.The method comprises the following steps: (1) under inert atmosphere, the metal organic framework material is calcined, and the metal in the metal organic framework material includes Co;(2) the calcination product is contacted with platinum source.The method of the present application is beneficial to the improvement of Pt utilization rate, and can effectively improve the activity of low Pt electrolytic water catalyst, and the HER overpotential of the catalyst is not higher than 80 mV under the current density of 10 mA / cm 2 .

Description

Technical Field

[0001] This invention relates to the field of electrocatalysts for hydrogen evolution reaction, specifically to electrocatalysts for hydrogen evolution reaction, their preparation methods, and applications. Background Technology

[0002] Compared to traditional hydrogen production technologies, water electrolysis is considered a highly efficient and environmentally friendly method due to its simpler production process, the use of water as a raw material, the high purity of the hydrogen produced, and the absence of pollutants. Developing efficient hydrogen evolution and oxygen evolution electrocatalysts can alter the electron transfer pathways and reaction energy barriers in the electrocatalytic water splitting process, thereby effectively reducing the reaction overpotential and improving the energy efficiency of water electrolysis. Pt / C catalysts, due to their high activity, are currently widely used commercial hydrogen evolution catalysts. However, their low reserves and high price limit their widespread application in water electrolysis hydrogen production. Therefore, developing efficient and low-cost hydrogen evolution catalysts is beneficial to the development of water electrolysis technology. Summary of the Invention

[0003] The purpose of this invention is to overcome the problems existing in the prior art and to provide an electrocatalyst for hydrogen evolution reaction, its preparation method, and its application.

[0004] To achieve the above objectives, a first aspect of the present invention provides a method for preparing an electrocatalyst for the hydrogen evolution reaction, the method comprising: (1) The metal-organic framework material is calcined under an inert atmosphere, wherein the metal in the metal-organic framework material includes Co; (2) Contact the calcined product with a platinum source.

[0005] A second aspect of the present invention provides an electrocatalyst for the hydrogen evolution reaction, which is prepared by the method described above; Alternatively, the catalyst comprises a support and Pt supported on the support, the elemental composition of the support comprising Co, C and N, and the loading of Pt being 1.7-4 wt%.

[0006] The third aspect of the present invention provides the application of the above-mentioned hydrogen evolution reaction electrocatalyst in the electrolysis of water to produce hydrogen.

[0007] Through the above technical solution, this invention uses Co metal-organic framework materials as precursors and obtains Co-C based catalysts through calcination. Due to the defect sites generated by high-temperature calcination, the noble metal Pt is adsorbed and coordinated with the surface defects of ZIF-derived carbides. Reducing the Pt particle size is beneficial to improving Pt atom utilization, which can effectively enhance the activity of low-Pt water electrolysis catalysts. At 10 mA / cm² 2 At the current density, the HER overpotential of this catalyst is no higher than 80mV. Attached Figure Description

[0008] Figure 1 This is a TEM image of Co-ZIF after high-temperature calcination in Example 1; Figure 2 This is a SEM image of Co-ZIF after high-temperature calcination in Example 2. Detailed Implementation

[0009] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0010] The first aspect of this invention provides a method for preparing an electrocatalyst for the hydrogen evolution reaction, the method comprising: (1) The metal-organic framework material is calcined under an inert atmosphere, wherein the metal in the metal-organic framework material includes Co; (2) Contact the calcined product with a platinum source.

[0011] In this invention, the organic ligand in the metal-organic framework material is not limited; Co can be loaded onto the organic framework, and it can be a metal-organic framework material commonly used in the art. Preferably, the organic ligand in the metal-organic framework material is provided by 2-methylimidazole.

[0012] In this invention, the preparation method of the metal-organic framework material is not limited and can be a common method for preparing metal-organic frameworks in the art. The metal-organic framework material can be obtained by mixing a cobalt source and an organic ligand in the presence of a first solvent.

[0013] Preferably, the metal-organic framework material is obtained by mixing a cobalt source with an organic ligand in the presence of a first solvent.

[0014] In this invention, for better mixing, when mixing the cobalt source and the organic ligand in the presence of the first solvent, the cobalt source can be mixed with the first solvent first, and then mixed with the mixture of the organic ligand and the first solvent.

[0015] In this invention, in order to obtain metal-organic framework materials, the mixed products can be centrifuged, washed, and dried.

[0016] In this invention, in order to load more Co onto the organic framework without causing waste, the molar ratio of Co to the organic ligand is 1:10-30, which can be any two values ​​of 1:10, 1:15, 1:20, 1:25, 1:30 or above, or any value within the range.

[0017] In this invention, in order to bind more Co to the organic framework, the mixing conditions include: a temperature of 20-40°C, which can be any two of the following values: 20°C, 25°C, 30°C, 35°C, 40°C or above; and a time of 8-15 hours, which can be any two of the following values: 8 hours, 9 hours, 10 hours, 11 hours, 12 hours, 13 hours, 14 hours, 15 hours or above.

[0018] In this invention, the cobalt source is not limited and can be any Co, preferably selected from Co(NO3)2 and / or cobalt chloride. In actual operation, it can be used in conjunction with bound water, preferably Co(NO3)2·6H2O.

[0019] In this invention, the first solvent is not limited and can be used to dissolve the cobalt source. The first solvent is selected from C1-C4 alcohols, preferably methanol.

[0020] In this invention, the organic ligand is not limited; it can provide an organic framework and can be loaded with a metal. The organic ligand is selected from 2-methylimidazole.

[0021] In this invention, the calcination conditions include: heating to 600°C or higher at a rate of 3-7°C / min, and maintaining this temperature for 0.5-5 hours, which can be any two values ​​within the range of 0.5h, 1h, 1.5h, 2h, 2.5h, 3h, 3.5h, 4h, 4.5h, 5h, or more; preferably, the heating rate can be any two values ​​within the range of 3°C / min, 4°C / min, 5°C / min, 6°C / min, 7°C / min, or more, preferably 4-6°C / min; more preferably, heating to 600-950°C, which can be any two values ​​within the range of 600°C, 650°C, 700°C, 750°C, 800°C, 850°C, 900°C, 950°C, or more; and even more preferably, the maintenance time is 1-3 hours. h can be any range formed by two or more values, such as 1h, 1.5h, 2h, 2.5h, 3h, or the values ​​within that range.

[0022] In this invention, the platinum source is not limited and can be any Pt source, preferably selected from PtCl4 and / or chloroplatinic acid.

[0023] In this invention, in order to prevent the calcination product from being mixed with other elements, the calcination is carried out under an inert atmosphere. Preferably, the inert atmosphere is provided by nitrogen and / or an inert gas, and more preferably by at least one of argon, helium and neon.

[0024] In this invention, to ensure that the calcined product is loaded with more Pt, the contact conditions include: first, ultrasonic contact at room temperature for 20-40 min (20 min, 25 min, 30 min, 35 min, 40 min or more, or any two values ​​within the range); then, contact at 50-70℃ (50℃, 55℃, 60℃, 65℃, 70℃ or more, or any two values ​​within the range) for 8-18 h (8h, 9h, 10h, 11h, 12h, 13h, 14h, 15h, 16h, 17h, 18h or more, or any two values ​​within the range).

[0025] In this invention, in order to load more Pt in the calcined product, the weight ratio of the calcined product to the platinum source is 10:0.05-0.5, which can be any two of the following values: 10:0.05, 10:0.1, 10:0.15, 10:0.2, 10:0.25, 10:0.3, 10:0.35, 10:0.4, 10:0.45, 10:0.5, or any value within the range formed by any two of the above values.

[0026] In this invention, in order to load Pt onto the calcined product, the contact is carried out in a second solvent. Preferably, the amount of platinum source relative to 1 mL of the second solvent is 0.1-1 mg, which can be any two of the following values: 0.1 mg, 0.2 mg, 0.3 mg, 0.4 mg, 0.5 mg, 0.6 mg, 0.7 mg, 0.8 mg, 0.9 mg, 1 mg, or a value within that range.

[0027] In this invention, in order to enable more Pt to be loaded in the calcination product, the pH of the contact system is 7.5-9.

[0028] In this invention, the second solvent is a polar weak base solvent, which allows the contact system to be within the above pH range and helps more Pt to be loaded in the calcined product. The second solvent is N-methylpyrrolidone.

[0029] In this invention, in order to enable the hydrogen evolution reaction electrocatalyst to catalyze the hydrogen evolution reaction in water electrolysis, the method further includes: reducing the solid in the product of step (2); preferably, the reduction conditions include: heating to 100-200℃ at a heating rate of 8-12℃ / min, which can be 8℃ / min, 8.5℃ / min, 9℃ / min, 9.5℃ / min, 10℃ / min, 10.5℃ / min, 11℃ / min, 11.5℃ / min, 12℃ / min or any two of the above values, and values ​​within that range, which can be 100℃, 110℃, 12℃ / min or any two of the above values. The temperature range is 20℃, 130℃, 140℃, 150℃, 160℃, 170℃, 180℃, 190℃, 200℃ or higher, and maintained at this temperature for 0.5-5 hours. The values ​​can be 0.5h, 1h, 1.5h, 2h, 2.5h, 3h, 3.5h, 4h, 4.5h, 5h or higher. More preferably, the reduction is carried out in the presence of hydrogen. Even more preferably, the flow rate of hydrogen and / or argon relative to 20-40mg of platinum source is 20-30mL / min, which can be 20 mL / min, 21 mL / min, 22 mL / min, 23 mL / min, 24 mL / min, 25 mL / min, 26 mL / min, 27 mL / min, 28 mL / min, 29 mL / min, 30 mL / min or higher.

[0030] In this invention, the solid in the product of step (2) is obtained by centrifugation, washing and drying of the product of step (2).

[0031] A second aspect of the present invention provides an electrocatalyst for the hydrogen evolution reaction, which is prepared by the method described above; Alternatively, the catalyst comprises a support and Pt supported on the support, the elemental composition of the support comprising Co, C and N, and the Pt loading (i.e. the Pt content in the catalyst) is 1.7-4 by weight. Preferably, the C content is 40-70% by weight of the carrier, which can be any two values ​​within the range of 40%, 45%, 50%, 55%, 60%, 65%, 70% or more; the Co content is 20-55% by weight of the carrier, which can be any two values ​​within the range of 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55% or more; the carrier also includes N, which is 1-5% by weight of the carrier, which can be any two values ​​within the range of 1%, 2%, 3%, 4%, 5% or more; the carrier also includes optional O, which is not more than 0.01% by weight of the carrier.

[0032] The third aspect of the present invention provides the application of the above-mentioned hydrogen evolution reaction electrocatalyst in the electrolysis of water to produce hydrogen.

[0033] Preferably, the hydrogen evolution reaction electrocatalyst is a cathode electrocatalyst; more preferably, the electrolysis is carried out under alkaline conditions.

[0034] In this invention, the catalyst can be applied to the electrode during practical use. Specifically, it can be ground, uniformly mixed with a solvent, and then dripped onto the electrode.

[0035] The present invention will be described in detail below through embodiments.

[0036] Example 1 First, 0.72 g of cobalt nitrate (Co(NO3)2·6H2O, 2.7 mmol) was weighed and mixed with 50 mL of methanol to obtain solution A. Then, 1.64 g of 2-methylimidazole (20 mmol) was mixed with 50 mL of methanol to obtain solution B. The two solutions were mixed evenly and stirred at room temperature for 12 h. The product was washed by centrifugation with ethanol to obtain Co-ZIF nanomaterials with a size of approximately 400-500 nm, which were then dried at 60 °C for later use.

[0037] 1 g of the dried sample was weighed and placed in a tube furnace. Under argon atmosphere, the argon flow rate was adjusted to 20 mL / min, and the temperature was increased to 700℃ at a heating rate of 5℃ / min. The temperature was maintained for 2 h, and then allowed to cool naturally to room temperature to obtain a black Co-C powder. The sample was observed under a transmission electron microscope (TEM). Figure 1As shown in the figure. According to the ICP results, the composition of the pyrolyzed sample is C: 50 wt%, Co: 45 wt%, N: 4.5 wt%, O: 0.1 wt%.

[0038] Weigh 30 mg of PtCl4 and mix it with 40 ml of NMP (N-methylpyrrolidone) at pH 8.5. Then add 0.3 g of Co-C black powder, sonicate at room temperature for half an hour, then heat and stir at 60°C for 12 hours. Add 10 ml of acetone solution, centrifuge, wash three times with ethanol solution, and dry in a 60°C oven for later use. Use a 10 v / v H2 / Ar mixture (H2 to Ar volume ratio of 1:9) at a flow rate of 25 mL / min, and heat to 150°C for 2 hours at a heating rate of 10°C / min. ICP test showed C: 49.2 wt%, Co: 44 wt%, N: 3.5 wt%, and Pt loading of 2.8 wt%.

[0039] The prepared catalyst was thoroughly ground. 10 mg of the catalyst was weighed and added to 1 mL of an ethanol solution containing Nafion (4% by volume) and 1 mL of isopropanol solution. The mixture was then ultrasonically dispersed. 20 μL of the dispersion (0.2 mg of catalyst) was measured and added dropwise to a rotating disk electrode for HER performance determination. Electrochemical testing was performed using a Shanghai Chenhua 760E electrochemical workstation. Before testing, N2 was passed through the electrolyte for approximately 30 min to saturate it. The three-electrode test system was then assembled, with the voltage range set to -0.1 to 0.1 V (vs. RHE) and the number of test cycles set to 20 to ensure complete sample activation and exposure of active sites. H2 was then passed through the electrolyte using a hydrogen generator for 30 min to completely saturate it. LSV testing was then performed at 0 to -0.6 V. 1 M KOH was used as the electrolyte, and the reaction was carried out at 10 mA / cm². 2 At the current density, the HER overpotential of this catalyst is 62 mV.

[0040] Example 2 The method was the same as in Example 1, except that the calcination temperature was 800°C. Scanning electron microscope images of the samples are shown below. Figure 2 As shown.

[0041] ICP testing showed C: 50 wt%, Co: 43.4 wt%, N: 2.5 wt%, and Pt loading of 3.8 wt%. This catalyst operates at 10 mA / cm². 2 At the current density, the HER overpotential is 53 mV.

[0042] Example 3 The method is the same as in Example 1, except that the calcination temperature is 900°C.

[0043] ICP testing showed C: 51.3 wt%, Co: 42 wt%, N: 2.3 wt%, and Pt loading of 4.1 wt%. This catalyst operates at 10 mA / cm². 2 At the current density, the HER overpotential is 52 mV.

[0044] Example 4 The method of Example 1 was followed, except that the concentration of the reaction solution was adjusted, i.e., 0.48 g (1.8 mmol) of cobalt nitrate was added to 50 mL of methanol solution to obtain Co-ZIF nanomaterials with different metal contents.

[0045] ICP testing showed C: 44.1 wt%, Co: 50 wt%, N: 4.0 wt%, and Pt loading of 1.9 wt%. This catalyst operates at 10 mA / cm². 2 At current density, the HER overpotential is 70mV.

[0046] Example 5 The method was the same as in Example 1, except that the concentration of the reaction solution was adjusted by adding 0.96 g (3.6 mmol) of cobalt nitrate to 50 mL of methanol solution.

[0047] ICP testing showed C: 54.2 wt%, Co: 38 wt%, N: 4.3 wt%, and Pt loading of 3.5 wt%. This catalyst operates at 10 mA / cm². 2 At current density, the HER overpotential is 58mV.

[0048] Example 6 The method was followed as in Example 1, except that the concentration of the reaction solution was adjusted. Specifically, 1.2 g of cobalt nitrate was weighed into 50 mL of methanol to obtain solution A, and then 3.28 g of 2-methylimidazole was mixed with 50 mL of methanol to obtain solution B. The Co-ZIF nanomaterials were obtained by mixing the above solutions.

[0049] ICP testing showed C: 41.2 wt%, Co: 52 wt%, N: 3.3 wt%, and Pt loading of 2.8 wt%. This catalyst operates at 10 mA / cm². 2 At current density, the HER overpotential is 70mV.

[0050] Example 7 The method was the same as in Example 1, except that the Pt ion concentration was reduced. Specifically, 13 mg of PtCl4 was weighed and mixed with 40 ml of NMP.

[0051] ICP analysis showed a Pt loading of 2.5 wt%. This catalyst operates at 10 mA / cm². 2 At current density, the HER overpotential is 74 mV.

[0052] Example 8 The method was followed as in Example 1, except that Pt was loaded using an aqueous solution impregnation method. 20 mg of PtCl4 was weighed and mixed with 40 mL of deionized water, then 0.3 g of Co-C black powder (synthesized according to the method in Example 1) was added. The mixture was sonicated for half an hour, followed by rotary evaporation at 60 degrees Celsius for 0.5 hours. Reduction was then carried out using a 10% (v / v) H2 / Ar mixed gas at a flow rate of 25 mL / min, heated to 150°C at a heating rate of 10°C / min for 2 hours.

[0053] ICP analysis showed a Pt loading of 4.6 wt%. Electrochemical performance testing was conducted at 10 mA / cm². 2 At current density, the HER overpotential is 85 mV.

[0054] The results above show that the catalyst obtained using the method of this invention exhibits higher water electrolysis catalyst activity with a lower Pt loading, and a smaller HER overpotential at the same current density. Comparing Example 1 with Examples 4-8 demonstrates that using appropriate Co source concentration, platinum source dosage, and platinum source loading method can yield better results.

[0055] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for preparing an electrocatalyst for the hydrogen evolution reaction, characterized in that, The method includes: (1) The metal-organic framework material is calcined under an inert atmosphere, wherein the metal in the metal-organic framework material is Co; (2) Contact the calcined product with a platinum source; the conditions for contacting the platinum source include: first ultrasonic contact at room temperature for 20-40 min, and then contact at 50-70℃ for 8-18 h. The method further includes: reducing the solid in the product of step (2); The reduction conditions include: heating to 100-200°C at a heating rate of 8-12°C / min, and maintaining at that temperature for 0.5-5 hours; The reduction is carried out in the presence of hydrogen gas; The metal-organic framework material is obtained by mixing a cobalt source with an organic ligand in the presence of a first solvent; The organic ligand in the metal-organic framework material is provided by 2-methylimidazole; The calcination conditions include: heating to 800-950°C at a rate of 3-7°C / min and maintaining that temperature for 0.5-5 hours; The weight ratio of the calcined product to the platinum source is 10:0.05-0.

5.

2. The method according to claim 1, wherein the molar ratio of Co to the organic ligand is 1:10-30.

3. The method according to claim 2, wherein, The cobalt source is selected from Co(NO3)2 and / or cobalt chloride; And / or, the first solvent is selected from C1-C4 alcohols; And / or, the mixing conditions include: a temperature of 20-40°C and a time of 8-15 hours.

4. The method according to claim 2, wherein, The first solvent is methanol.

5. The method according to claim 1 or 2, wherein, The platinum source is selected from PtCl4 and / or chloroplatinic acid.

6. The method according to claim 1, wherein, The heating rate is 4-6℃ / min; And / or, the duration of the maintenance is 1-3 hours.

7. The method according to claim 1, wherein, The contact takes place in a second solvent.

8. The method according to claim 7, wherein, The amount of the platinum source relative to 1 mL of the second solvent is 0.1-1 mg; And / or, the second solvent is N-methylpyrrolidone.

9. The method according to claim 1 or 2, wherein, The hydrogen flow rate is 20-30 mL / min relative to 20-40 mg of platinum source.

10. An electrocatalyst for hydrogen evolution reaction, characterized in that, The catalyst is prepared by any one of the methods in claims 1-9; Alternatively, the catalyst comprises a support and Pt supported on the support, the elemental composition of the support comprising Co, C and N, and the loading of Pt being 1.7-4 by weight.

11. The application of the hydrogen evolution reaction electrocatalyst according to claim 10 in the electrolysis of water to produce hydrogen.

12. The application according to claim 11, wherein, The hydrogen evolution reaction electrocatalyst is a cathode electrocatalyst; And / or, the electrolysis is carried out under alkaline conditions.

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