A vanadium-cobalt-nickel ternary phosphide and its preparation method and application

Abstract

The present invention relates to the technical field of electrolytic hydrogen evolution catalysts, and in particular to a vanadium-cobalt-nickel ternary phosphide, its preparation method, and application. The preparation method provided by the present invention comprises the following steps: mixing a first soluble vanadium salt, a first soluble cobalt salt, a first soluble nickel salt, a reaction aid, and water, adding nickel foam, and performing a first hydrothermal reaction to obtain a first nickel foam containing a hydroxide precursor; mixing the first nickel foam containing a hydroxide precursor, a second soluble vanadium salt, a second soluble cobalt salt, a second soluble nickel salt, ammonium fluoride, trisodium citrate, and water, and performing a second hydrothermal reaction to obtain a second nickel foam containing a hydroxide precursor; and subjecting the second nickel foam containing a hydroxide precursor to a vapor phase phosphating treatment to obtain the vanadium-cobalt-nickel ternary phosphide. The vanadium-cobalt-nickel ternary phosphide prepared by the preparation method has high hydrogen evolution catalytic activity and is low in cost.

Description

Technical Field

[0001] The present invention relates to the technical field of electrohydrogen evolution catalysts, and in particular to a vanadium-cobalt-nickel ternary phosphide and a preparation method and application thereof. Background Art

[0002] Hydrogen is considered a mid-level energy source for resolving energy and environmental challenges. Using renewable energy to electrolyze water to produce hydrogen is considered a viable approach. However, current electrolyzers for hydrogen production typically use platinum-group precious metals as catalysts, which are expensive and difficult to implement on a large scale. Therefore, the development of lower-cost electrolyzers is crucial, with the development of low-cost, high-performance hydrogen evolution catalysts being a top priority. Summary of the Invention

[0003] The object of the present invention is to provide a vanadium-cobalt-nickel ternary phosphide and a preparation method and application thereof. The vanadium-cobalt-nickel ternary phosphide prepared by the preparation method has high hydrogen evolution catalytic activity and low cost.

[0004] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0005] The present invention provides a method for preparing ternary vanadium-cobalt-nickel phosphide, comprising the following steps:

[0006] After mixing a first soluble vanadium salt, a first soluble cobalt salt, a first soluble nickel salt, a reaction aid and water, adding nickel foam, and performing a first hydrothermal reaction to obtain a first nickel foam containing a hydroxide precursor;

[0007] Mixing the first nickel foam containing a hydroxide precursor, a second soluble vanadium salt, a second soluble cobalt salt, a second soluble nickel salt, ammonium fluoride, trisodium citrate, and water, and performing a second hydrothermal reaction to obtain a second nickel foam containing a hydroxide precursor;

[0008] The second nickel foam containing the hydroxide precursor is subjected to a gas phase phosphating treatment to obtain the vanadium-cobalt-nickel ternary phosphide.

[0009] Preferably, the reaction aid comprises CO(NH2)2 and NH4F;

[0010] The molar ratio of CO(NH2)2 and NH4F is (4-6):(5-7).

[0011] Preferably, the molar ratio of the first soluble vanadium salt, the first soluble cobalt salt, the first soluble nickel salt and the reaction aid is (0.2-0.5):(0.4-0.6):(0.5-0.8):(9-13).

[0012] Preferably, the temperature of the first hydrothermal reaction is 120-180° C., and the time is 16-24 hours.

[0013] Preferably, the molar ratio of the first soluble vanadium salt, the second soluble vanadium salt, the second soluble cobalt salt, the second soluble nickel salt, ammonium fluoride and trisodium citrate is (0.2-0.5):(0.2-0.5):0.5:(0.5-0.8):(5-7):(0.2-0.25).

[0014] Preferably, the temperature of the second hydrothermal reaction is 120-180° C., and the time is 4-8 hours.

[0015] Preferably, the gas used in the gas phase phosphating treatment is phosphine gas;

[0016] The phosphine gas is obtained by thermal decomposition of NaH2PO2·H2O.

[0017] Preferably, the temperature of the vapor phase phosphating treatment is 350-450° C., and the time is 2-4 hours.

[0018] The present invention also provides vanadium-cobalt-nickel ternary phosphide prepared by the preparation method described in the above technical solution.

[0019] The present invention also provides the use of the vanadium-cobalt-nickel ternary phosphide described in the above technical solution in the field of electrochemical hydrogen evolution.

[0020] The present invention provides a method for preparing a vanadium-cobalt-nickel ternary phosphide, comprising the following steps: mixing a first soluble vanadium salt, a first soluble cobalt salt, a first soluble nickel salt, a reaction aid, and water, adding nickel foam, and performing a first hydrothermal reaction to obtain a first nickel foam containing a hydroxide precursor; mixing the first nickel foam containing a hydroxide precursor, a second soluble vanadium salt, a second soluble cobalt salt, a second soluble nickel salt, ammonium fluoride, trisodium citrate, and water, and performing a second hydrothermal reaction to obtain a second nickel foam containing a hydroxide precursor; and subjecting the second nickel foam containing a hydroxide precursor to a vapor phase phosphating treatment to obtain the vanadium-cobalt-nickel ternary phosphide. The present invention utilizes a step-by-step hydrothermal process to grow more hydroxide precursors on the surface of the foam substrate, and to make the hydroxide precursors grow more uniformly, generating more active sites, thereby improving their catalytic activity. At the same time, the present invention uses three non-precious metal elements to synthesize the precursor. The three metal elements work synergistically to obtain a catalyst with superior performance. To a certain extent, it can replace traditional precious metal catalysts, greatly reducing the synthesis cost of the catalyst (the cost price of vanadium is about 1.9 yuan / g, the cost price of cobalt is about 0.357 yuan / g, the cost price of nickel is about 0.17 yuan / g, and the cost price of platinum is about 190 yuan / g); foam nickel is used as the substrate, and the catalyst is directly grown on its surface. There is a chemical bond between the catalyst and the substrate, rather than relying on a single intermolecular force to combine, so the catalyst is more tightly bound to the substrate and has higher stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is the element distribution diagram of the vanadium-cobalt-nickel ternary phosphide described in Example 1;

[0022] Figure 2 Polarization curves of the vanadium-cobalt-nickel ternary phosphide and the pretreated nickel foam described in Examples 1 to 4;

[0023] Figure 3 Polarization curves of the vanadium-cobalt-nickel ternary phosphide and the commercial 20% Pt / C catalyst described in Example 3;

[0024] Figure 4 This is the stability curve of the vanadium-cobalt-nickel ternary phosphide described in Example 1. DETAILED DESCRIPTION

[0025] The present invention provides a method for preparing ternary vanadium-cobalt-nickel phosphide, comprising the following steps:

[0026] After mixing a first soluble vanadium salt, a first soluble cobalt salt, a first soluble nickel salt, a reaction aid and water, adding nickel foam, and performing a first hydrothermal reaction to obtain a first nickel foam containing a hydroxide precursor;

[0027] Mixing the first nickel foam containing a hydroxide precursor, a second soluble vanadium salt, a second soluble cobalt salt, a second soluble nickel salt, ammonium fluoride, trisodium citrate, and water, and performing a second hydrothermal reaction to obtain a second nickel foam containing a hydroxide precursor;

[0028] The second nickel foam containing the hydroxide precursor is subjected to a gas phase phosphating treatment to obtain the vanadium-cobalt-nickel ternary phosphide.

[0029] In the present invention, unless otherwise specified, all preparation raw materials are commercially available products well known to those skilled in the art.

[0030] The present invention mixes a first soluble vanadium salt, a first soluble cobalt salt, a first soluble nickel salt, a reaction aid and water, adds foamed nickel, and performs a first hydrothermal reaction to obtain a first foamed nickel containing a hydroxide precursor.

[0031] The present invention does not specifically limit the types of the first soluble vanadium salt, the first soluble cobalt salt, and the first soluble nickel salt; any of the types known to those skilled in the art may be used. In an embodiment of the present invention, the first soluble vanadium salt is specifically vanadium trichloride; the first soluble cobalt salt is specifically cobalt dichloride hexahydrate; and the first soluble nickel salt is specifically nickel dichloride hexahydrate.

[0032] In the present invention, the reaction aid preferably includes CO(NH2)2 and NH4F; the molar ratio of CO(NH2)2 and NH4F is preferably (4-6):(5-7), more preferably 5:6.

[0033] In the present invention, the molar ratio of the first soluble vanadium salt, the first soluble cobalt salt, the first soluble nickel salt and the reaction aid is preferably (0.2-0.5):(0.4-0.6):(0.5-0.8):(9-13), more preferably (0.2-0.5):0.5:(0.5-0.8):11, further preferably (0.3-0.4):0.5:(0.6-0.7):11, and most preferably 0.4:0.5:0.6:11.

[0034] In the present invention, the usage ratio of the first soluble vanadium salt to water is preferably 0.4 mmol:30 mL.

[0035] The present invention does not have any special limitation on the mixing process, and the mixing process may be carried out using a process well known to those skilled in the art.

[0036] The present invention does not have any special restrictions on the type of nickel foam, and any type known to those skilled in the art can be used. In the embodiment of the present invention, the nickel foam specifically has a surface density of 350g / m 2 , with a specific surface area of ​​0.08 cm2 / g, a pore density of 110ppi, a porosity of 98%, and a nickel foam containing 99.9wt%.

[0037] Before adding the nickel foam, the present invention also preferably includes pre-treating the nickel foam, wherein the pre-treatment includes sequentially trimming and cleaning. The present invention does not have any particular limitations on the trimming process, and the process can be performed using a process well known to those skilled in the art. In the present invention, the cleaning is preferably performed sequentially using acetone, a 3 mol / L hydrochloric acid solution, and anhydrous ethanol for 15 minutes. In the present invention, the purpose of the cleaning is to remove organic matter and oxide layers remaining on the surface of the nickel foam during surface processing.

[0038] In the present invention, the temperature of the first hydrothermal reaction is preferably 120-180°C, more preferably 130-160°C, and most preferably 140-150°C; the time is preferably 16-24 hours, more preferably 18-22 hours, and most preferably 19-20 hours. In an embodiment of the present invention, the first hydrothermal reaction is preferably carried out by placing 30 mL of the reaction system obtained by the first hydrothermal reaction into a 40 mL Teflon-lined stainless steel autoclave.

[0039] After the first hydrothermal reaction is completed, the present invention also preferably includes sequential washing and drying; the washing is preferably performed using water and ethanol in sequence; the present invention does not have any special limitation on the drying process, and the process well known to those skilled in the art can be used.

[0040] After obtaining the first nickel foam containing a hydroxide precursor, the present invention mixes the first nickel foam containing a hydroxide precursor, a second soluble vanadium salt, a second soluble cobalt salt, a second soluble nickel salt, ammonium fluoride, trisodium citrate and water, and performs a second hydrothermal reaction to obtain a second nickel foam containing a hydroxide precursor.

[0041] The present invention does not impose any particular restrictions on the types of the second soluble vanadium salt, the second soluble cobalt salt, and the second soluble nickel salt; any of the types known to those skilled in the art may be used. In an embodiment of the present invention, the second soluble vanadium salt is specifically vanadium trichloride; the second soluble cobalt salt is specifically cobalt dichloride hexahydrate; and the second soluble nickel salt is specifically nickel dichloride hexahydrate.

[0042] In the present invention, the molar ratio of the first soluble vanadium salt, the second soluble vanadium salt, the second soluble cobalt salt, the second soluble nickel salt, ammonium fluoride and trisodium citrate is preferably (0.2-0.5): (0.2-0.5):0.5: (0.5-0.8): (5-7): (0.2-0.25), more preferably (0.2-0.5): (0.2-0.5): 0.5: (0.5-0.8): 6:0.2, further preferably (0.3-0.4): (0.3-0.4): 0.5: (0.6-0.7): 6:0.2, and most preferably 0.4:0.4:0.5:0.6:6:0.2.

[0043] In the present invention, the temperature of the second hydrothermal reaction is preferably 120-180°C, more preferably 130-160°C, and most preferably 140-150°C; the time is preferably 4-8 hours, more preferably 5-6 hours. In an embodiment of the present invention, the second hydrothermal reaction is preferably carried out by placing 30 mL of the reaction system obtained by the second hydrothermal reaction into a 40 mL Teflon-lined stainless steel autoclave.

[0044] After the second hydrothermal reaction is completed, the present invention preferably further comprises cleaning; the cleaning is preferably performed using water and ethanol in sequence.

[0045] After obtaining the second nickel foam containing a hydroxide precursor, the present invention performs a vapor phase phosphating treatment on the second nickel foam containing a hydroxide precursor to obtain the vanadium-cobalt-nickel ternary phosphide.

[0046] In the present invention, the gas used in the gas-phase phosphating treatment is preferably phosphine gas; the phosphine gas is preferably obtained by thermal decomposition of NaH2PO2·H2O.

[0047] In the present invention, the temperature of the vapor phase phosphating treatment is preferably 350-450°C, more preferably 380-420°C, and most preferably 400°C; the time is preferably 2-4 hours, more preferably 2-3 hours. In the present invention, the vapor phase phosphating treatment is preferably carried out in an argon atmosphere.

[0048] In the present invention, the process of the gas phase phosphating treatment is preferably to place NaH2PO2·H2O upstream of a tube furnace, and to place the second nickel foam containing a hydroxide precursor downstream of the tube furnace, and to heat and perform the gas phase phosphating treatment.

[0049] The present invention also provides vanadium-cobalt-nickel ternary phosphide prepared by the preparation method described in the above technical solution.

[0050] The present invention also provides the use of the vanadium-cobalt-nickel ternary phosphide described in the above technical solution in the field of electrochemical hydrogen evolution. The present invention does not have any special restrictions on the method of the application, and the method well known to those skilled in the art can be used.

[0051] The vanadium-cobalt-nickel ternary phosphide provided by the present invention, its preparation method and application are described in detail below with reference to the examples, but they should not be construed as limiting the scope of protection of the present invention.

[0052] Example 1

[0053] The surface density is 350g / m 2 , with a specific surface area of ​​0.08 cm 2 / g, pore density 110ppi, porosity 98%, nickel content 99.9wt% nickel foam was cut into 1.5×4cm 2 Then, the nickel foam was washed with acetone, 3 mol / L hydrochloric acid solution and anhydrous ethanol for 15 min in sequence to obtain pretreated nickel foam.

[0054] 0.4 mmol of vanadium trichloride, 0.5 mmol of cobalt dichloride hexahydrate, 0.6 mmol of nickel dichloride hexahydrate, 5 mmol of CO(NH2)2, 6 mmol of NH4F and 30 mL of water were mixed, and the mixture was placed in a 40 mL Teflon-lined stainless steel autoclave. The pretreated nickel foam was added and subjected to a hydrothermal reaction at 140° C. for 20 h. The mixture was washed with water and ethanol in sequence and dried to obtain a first nickel foam containing a hydroxide precursor.

[0055] The first nickel foam containing a hydroxide precursor, 0.4 mmol vanadium trichloride, 0.5 mmol cobalt dichloride hexahydrate, 0.6 mmol nickel dichloride hexahydrate, 6 mmol NH4F, 0.2 mmol trisodium citrate and 30 mL water were mixed, placed in a 40 mL Teflon-lined stainless steel autoclave, and subjected to hydrothermal reaction at 140°C for 5 h. The mixture was then rinsed with water and ethanol in sequence and dried to obtain a second nickel foam containing a hydroxide precursor;

[0056] NaH2PO2·H2O is placed upstream of a tube furnace, and the second nickel foam containing a hydroxide precursor is placed downstream of the tube furnace. The mixture is heated at 400°C for 2 hours in an argon atmosphere to perform a vapor phase phosphating treatment to obtain vanadium-cobalt-nickel ternary phosphide (molar ratio: V:Co:Ni=0.4:0.5:0.6);

[0057] Figure 1 is the element distribution diagram of the vanadium-cobalt-nickel ternary phosphide, Figure 1 It can be seen that V, Co, Ni and P in the vanadium-cobalt-nickel ternary phosphide are uniformly distributed in the vanadium-cobalt-nickel ternary phosphide.

[0058] Example 2

[0059] Refer to Example 1, with the difference that: when preparing the first nickel foam containing a hydroxide precursor, the amounts of vanadium trichloride, cobalt dichloride hexahydrate and nickel dichloride hexahydrate are 0.5 mmol, 0.5 mmol and 0.5 mmol, respectively; when preparing the second nickel foam containing a hydroxide precursor, the amounts of vanadium trichloride, cobalt dichloride hexahydrate and nickel dichloride hexahydrate are 0.5 mmol, 0.5 mmol and 0.5 mmol, respectively, to prepare vanadium cobalt nickel ternary phosphide (molar ratio: V: Co: Ni = 0.5:0.5:0.5).

[0060] Example 3

[0061] Refer to Example 1, with the difference that: when preparing the first nickel foam containing a hydroxide precursor, the amounts of vanadium trichloride, cobalt dichloride hexahydrate and nickel dichloride hexahydrate are 0.3 mmol, 0.5 mmol and 0.7 mmol, respectively; when preparing the second nickel foam containing a hydroxide precursor, the amounts of vanadium trichloride, cobalt dichloride hexahydrate and nickel dichloride hexahydrate are 0.3 mmol, 0.5 mmol and 0.7 mmol, respectively, to prepare vanadium cobalt nickel ternary phosphide (molar ratio: V: Co: Ni = 0.3:0.5:0.7).

[0062] Example 4

[0063] Refer to Example 1, with the difference that: when preparing the first nickel foam containing a hydroxide precursor, the amounts of vanadium trichloride, cobalt dichloride hexahydrate and nickel dichloride hexahydrate are 0.2 mmol, 0.5 mmol and 0.8 mmol, respectively; when preparing the second nickel foam containing a hydroxide precursor, the amounts of vanadium trichloride, cobalt dichloride hexahydrate and nickel dichloride hexahydrate are 0.2 mmol, 0.5 mmol and 0.8 mmol, respectively, to prepare vanadium cobalt nickel ternary phosphide (molar ratio: V: Co: Ni = 0.2:0.5:0.8).

[0064] Test Case

[0065] The vanadium-cobalt-nickel ternary phosphide and pretreated nickel foam described in Examples 1 to 4 were tested for electrocatalytic hydrogen evolution performance. The test process was as follows: all tests were carried out in a standard three-electrode system, and the test instrument was a Shanghai Chenhua CHI660E electrochemical workstation; the prepared samples were cut into appropriate sizes and used as working electrodes, Hg / HgO electrodes were used as reference electrodes, platinum electrodes were used as counter electrodes, 1 mol / L KOH solution was used as electrolyte, and the test temperature was kept constant at 25°C. Before the test, cyclic voltammetry was used to make the catalyst reach a relatively stable state, and linear sweep voltammetry (LSV) tests were performed after 30 cyclic voltammetry scans. All potentials have been converted to standard hydrogen electrode potentials (vs. RHE);

[0066] Polarization curves such as Figure 2 As shown by Figure 2 It can be seen that the vanadium-cobalt-nickel ternary phosphide described in Example 1 in Examples 1 to 4 has a current density of 1000 mA / cm 2 When the overpotential is only 266 mV, it shows excellent electrocatalytic hydrogen evolution performance, which is similar to the electrocatalytic performance of commercial platinum-carbon catalysts.

[0067] Figure 3 The polarization curves of the vanadium-cobalt-nickel ternary phosphide and the commercial 20% Pt / C catalyst described in Example 3 are shown in FIG. Figure 3 It can be seen that the electrocatalytic performance of the vanadium-cobalt-nickel ternary phosphide described in Example 2 is similar to that of the commercial platinum-carbon catalyst;

[0068] The electrocatalytic stability of the vanadium-cobalt-nickel ternary phosphide described in Example 1 was tested in a standard three-electrode system using a Shanghai Chenhua CHI660E electrochemical workstation. The prepared sample was cut into appropriate sizes and used as the working electrode, a Hg / HgO electrode as the reference electrode, a carbon rod electrode as the counter electrode, and a 1 mol / L KOH solution as the electrolyte. The test temperature was maintained at 25°C and the test potential was -130 mV (vs. RHE). The stability curve is shown in Figure 2. Figure 4 As shown by Figure 4 It can be seen that the catalytic performance of the vanadium-cobalt-nickel ternary phosphide described in Example 1 has no visible attenuation after continuous operation for 12 hours.

[0069] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. An application of vanadium-cobalt-nickel ternary phosphide in the field of electrochemical hydrogen evolution, characterized in that: The preparation method of the vanadium-cobalt-nickel ternary phosphide comprises the following steps: After mixing a first soluble vanadium salt, a first soluble cobalt salt, a first soluble nickel salt, a reaction aid and water, adding nickel foam, and performing a first hydrothermal reaction to obtain a first nickel foam containing a hydroxide precursor; Mixing the first nickel foam containing a hydroxide precursor, a second soluble vanadium salt, a second soluble cobalt salt, a second soluble nickel salt, ammonium fluoride, trisodium citrate, and water, and performing a second hydrothermal reaction to obtain a second nickel foam containing a hydroxide precursor; performing a gas-phase phosphating treatment on the second nickel foam containing the hydroxide precursor to obtain the vanadium-cobalt-nickel ternary phosphide; The reaction aids include CO(NH2)2 and NH4F; The molar ratio of CO(NH2)2 and NH4F is (4-6):(5-7); The molar ratio of the first soluble vanadium salt, the first soluble cobalt salt, the first soluble nickel salt and the reaction aid is (0.2-0.5):(0.4-0.6):(0.5-0.8):(9-13); The molar ratio of the first soluble vanadium salt, the second soluble vanadium salt, the second soluble cobalt salt, the second soluble nickel salt, ammonium fluoride and trisodium citrate is (0.2-0.5):(0.2-0.5):0.5:(0.5-0.8):(5-7):(0.2-0.25).

2. The use according to claim 1, characterized in that The temperature of the first hydrothermal reaction is 120-180° C., and the time is 16-24 hours.

3. The use according to claim 1, characterized in that The temperature of the second hydrothermal reaction is 120-180° C., and the time is 4-8 hours.

4. The use according to claim 1, wherein The gas used in the gas phase phosphating treatment is phosphine gas; The phosphine gas is obtained by thermal decomposition of NaH2PO2·H2O.

5. The use according to claim 1 or 4, characterized in that The temperature of the gas phase phosphating treatment is 350-450° C., and the time is 2-4 hours.

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