Nickel-vanadium-based composite catalyst as well as preparation method and application thereof

Abstract

The invention discloses a nickel-vanadium-based composite catalyst as well as a preparation method and application thereof. The nickel-vanadium-based composite catalyst is prepared from a Ni-S compound and Ni3V. Through sulfuration doping, a catalytic site with high activity can be generated in situ, and the conductivity of the catalytic material is remarkably improved. The nickel-vanadium-based composite catalyst disclosed by the invention shows relatively good oxygen evolution performance.

Description

Technical Field

[0001] This invention relates to the field of hydrogen production by water electrolysis, specifically to a nickel-vanadium based composite catalyst, its preparation method, and its application in electrocatalytic oxygen evolution. Background Technology

[0002] With the global energy crisis worsening and drastic climate change occurring, the Earth is facing serious environmental problems. To address environmental issues such as global warming and resource shortages, developing green, renewable, and clean energy sources to replace fossil fuels has become a hot research topic in the energy industry. Hydrogen energy, as a clean energy source, holds the promise of replacing traditional fossil fuels.

[0003] With the advancement of technology, various methods for producing hydrogen have been developed. Among them, the water electrolysis method uses water as raw material, produces no pollutants during the electrolysis process, and has a relatively simple production process. Therefore, it is considered an efficient, environmentally friendly, and sustainable hydrogen production technology with broad application prospects.

[0004] Anion exchange membrane electrolysis of water uses anion exchange membranes (AEMs) as the diaphragm and low- or non-precious metals as catalysts. Compared to traditional alkaline water electrolysis technology, it can use low-concentration alkaline solutions or water as the electrolyte, giving it multiple advantages such as low cost and high efficiency, making it a promising water electrolysis technology for the future.

[0005] Developing highly active hydrogen evolution and oxygen evolution catalysts is an effective way to reduce energy consumption in water electrolysis. While precious metal catalysts exhibit high activity in the catalytic oxygen evolution process, their high cost due to low precious metal content hinders their commercial application. Therefore, it is crucial to research and develop low-cost, simple-to-prepare, and highly active oxygen evolution catalytic electrodes.

[0006] Although numerous studies on OER electrocatalysts in alkaline media have been reported in the literature, their application in AEM is still relatively limited. Oxides and hydroxides have attracted widespread attention due to their low cost and good oxygen evolution reaction activity, but they still fall short of practical application requirements, and their performance and stability need further improvement. Summary of the Invention

[0007] To address the problems existing in the prior art, this invention develops a low-cost, high-performance electrocatalytic oxygen evolution catalyst.

[0008] One objective of this invention is to provide a nickel-vanadium based composite catalyst, comprising Ni-S compounds and Ni3V.

[0009] The nickel-vanadium-based composite catalyst material of the present invention has a composite structure of an external sulfide (Ni-S compound) and an internal metal alloy (Ni3V).

[0010] In the nickel-vanadium-based composite catalyst, the molar ratio of Ni3V to Ni-S compound is (2-10):1, preferably (2-5):1, for example, it can be 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, etc.

[0011] The size of the nickel-vanadium-based composite catalyst is 20–100 nm, preferably 20–60 nm.

[0012] The Ni-S / Ni3V composite catalyst of the present invention improves the oxygen vacancy density of the material by Ni-S doping, thereby enhancing the material's charge transfer capability and oxygen evolution performance.

[0013] The second objective of this invention is to provide a method for preparing the nickel-vanadium-based composite catalyst described in the first objective of this invention:

[0014] The process involves mixing a sulfur-containing nickel source and a sulfur-containing vanadium source with water, adding an alkaline solution, and performing hydrothermal crystallization to obtain a nickel-vanadium-based precursor, which is then calcined in an inert gas / H2 atmosphere.

[0015] According to the present invention, the sulfur-containing nickel source is selected from nickel sulfate.

[0016] According to the present invention, the sulfur-containing vanadium source is selected from vanadium oxysulfate.

[0017] According to the present invention, the alkaline solution is selected from at least one of potassium hydroxide solution, sodium hydroxide solution, and ammonia water.

[0018] According to the present invention, the molar ratio of nickel source to vanadium source is (4-8):1, for example, it can be 4:1, 5:1, 6:1, 7:1, 8:1, etc.

[0019] According to the present invention, the concentration of the alkaline solution is 1 to 2.5 M, for example, it can be 1 M, 1.5 M, 2 M, 2.5 M, etc.

[0020] According to the present invention, the molar ratio of alkaline solution to vanadium source is (4 to 10):1, for example, it can be 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, etc.

[0021] According to the present invention, the temperature for hydrothermal crystallization is 100–180°C, and the time is 20–28 h.

[0022] According to the present invention, preferably, the hydrothermal crystallization temperature is 100-160°C and the time is 23-26 hours.

[0023] According to the present invention, the heating rate of calcination is 4 to 8 °C / min, preferably 4 to 6 °C / min.

[0024] According to the present invention, the calcination temperature is 360–580°C and the time is 2–4 hours.

[0025] According to the present invention, preferably, the calcination temperature is 370-550°C and the time is 2-3 hours.

[0026] This invention employs a one-step hydrothermal method to synthesize a nanocomposite structure consisting of an external sulfide and an internal metal alloy, namely a Ni-S / Ni3V composite catalyst with a size of 20–100 nm. Ni-S doping increases the oxygen vacancy density of the material, thereby enhancing its charge transfer capability and oxygen evolution performance.

[0027] A third objective of this invention is to provide the application of the nickel-vanadium-based composite catalyst described in one objective of this invention or the nickel-vanadium-based composite catalyst obtained by the preparation method described in another objective of this invention in the electrocatalytic oxygen evolution process.

[0028] Specifically, the nickel-vanadium-based composite catalyst can be used in alkaline membrane water electrolysis processes.

[0029] The beneficial effects of this invention are:

[0030] This invention, through sulfide doping, can generate highly active catalytic sites in situ, significantly improving the conductivity of catalytic materials.

[0031] The nickel-vanadium-based composite catalyst described in this invention exhibits good oxygen evolution performance at a current density of 10 mA / cm². 2 At that time, the oxygen evolution overpotential can reach 278mV. However, at the same 10mA / cm², the oxygen evolution overpotential can reach 278mV. 2 At the current density, the oxygen evolution overpotential of IrO2 is about 350mV. Attached Figure Description

[0032] Figure 1 SEM image of the sample in Example 1.

[0033] from Figure 1 As can be seen, the product (nickel-vanadium-based composite catalyst) is in the form of particles with a size of approximately 20–50 nm.

[0034] Figure 2 EDS image of the sample in Example 1.

[0035] from Figure 2 The product contains elements such as Ni, V, and S.

[0036] Figure 3 XRD pattern of the sample in Example 1.

[0037] from Figure 3The product contains Ni3V and Ni-S compounds.

[0038] Figure 4 XPS image of the sample in Example 1.

[0039] from Figure 4 The product surface contains Ni-S compounds.

[0040] Figure 5 LSV polarization curves of the sample in Example 1.

[0041] from Figure 5 The nickel-vanadium-based composite catalyst can be seen at a current density of 10 mA / cm². 2 At that time, the oxygen evolution overpotential was 278mV.

[0042] Figure 6 Tafel plot of the sample in Example 1.

[0043] from Figure 6 As can be seen, the slope of Tafel is 89mv / dec.

[0044] Figure 7 SEM image of the sample in Example 2.

[0045] from Figure 7 The product can be seen to be in the form of particles with a size of approximately 30–60 nm. Detailed Implementation

[0046] The present invention will now be described in detail with reference to the accompanying drawings and embodiments. It should be noted that the following embodiments are only used to further illustrate the present invention and should not be construed as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the content of the present invention are still within the scope of protection of the present invention.

[0047] It should also be noted that the various specific technical features described in the following embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, the various possible combinations will not be described separately in this invention.

[0048] Furthermore, various embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention. The resulting technical solutions are part of the original disclosure of this specification and also fall within the protection scope of the present invention.

[0049] 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.

[0050] Unless otherwise specified, the raw materials used in the examples and comparative examples are all disclosed in the prior art, such as those that can be directly purchased or prepared according to the preparation methods disclosed in the prior art.

[0051] To achieve the above objectives, the first aspect of the present invention provides a nickel-vanadium-based composite catalyst, which is an oxygen evolution electrode catalyst. The catalyst is a nanocomposite structure of an external sulfide and an internal metal alloy, namely a Ni-S / Ni3V composite catalyst.

[0052] According to some preferred embodiments of the present invention, the molar ratio of Ni3V to Ni-S in the catalyst is 2 to 10:1, preferably 2 to 5:1.

[0053] According to some preferred embodiments of the present invention, the particle size of the catalyst nanostructure is 20-100 nm.

[0054] A second aspect of the present invention provides a method for preparing an oxygen evolution electrode catalyst.

[0055] According to a preferred embodiment of the present invention, the method includes:

[0056] Sulfur-containing nickel salt and sulfur-containing vanadium salt were dissolved and uniformly mixed. Then, a certain concentration of alkaline solution was added dropwise and mixed thoroughly. The solution was placed in a reactor for hydrothermal crystallization at a certain temperature and time. After filtration and vacuum drying, the solution was calcined in a tube furnace under an inert gas / H2 atmosphere at a certain temperature and time.

[0057] According to some preferred embodiments of the present invention, the sulfur-containing nickel salt may be nickel sulfate.

[0058] According to some preferred embodiments of the present invention, the sulfur-containing vanadium salt may be vanadium oxysulfate.

[0059] According to some preferred embodiments of the present invention, the alkaline solution may be potassium hydroxide solution, sodium hydroxide solution, ammonia water, etc.

[0060] According to some preferred embodiments of the present invention, the concentration of the alkali solution in the reaction solution is 1 to 2.5 M.

[0061] According to some preferred embodiments of the present invention, the molar ratio of alkali solution to vanadium source in the reaction solution is 4 to 10:1.

[0062] According to some preferred embodiments of the present invention, the molar ratio of nickel source to vanadium source in the reaction solution is 4 to 8:1.

[0063] According to some preferred embodiments of the present invention, the inert gas may be Ar or the like.

[0064] According to some preferred embodiments of the present invention, the hydrogen content in the calcining atmosphere is 5-15 wt%.

[0065] According to some preferred embodiments of the present invention, the temperature of the reactor is 100-180°C and the reaction time is 20-28h.

[0066] According to some preferred embodiments of the present invention, the temperature of the tube furnace is 360–580°C, and the calcination time is 2–4 hours.

[0067] According to some preferred embodiments of the present invention, the heating rate of the tube furnace is 4 to 8 °C / min.

[0068] According to some preferred embodiments of the present invention, the preparation of the catalyst may include the following steps:

[0069] NiSO4, VOSO4, and deionized water (30 mL) were mixed and stirred for 10 minutes. Then, KOH solution, NaOH solution, or ammonia solution was added dropwise, and stirring continued for another 10 minutes. Subsequently, the mixture was placed in a Teflon pressure reactor for hydrothermal crystallization. Finally, the solution was filtered with deionized water, and the recovered solid was vacuum dried overnight to obtain the nickel-vanadium-based precursor. The synthesized nickel-vanadium-based precursor was calcined in a 10 wt% H2 / Ar atmosphere.

[0070] In this invention, the electrode slurry is prepared as follows:

[0071] First, the Ni-S / Ni3V composite catalyst was ground. 10 mg of the catalyst was weighed and added to 1 mL of isopropanol and 1 mL of Nafion, and ultrasonically dispersed for 30 min. Five 5 μL portions of the dispersion were then added dropwise to a rotating disk electrode for testing its oxygen evolution performance in water electrolysis.

[0072] A three-electrode system was constructed using a rotating disk electrode with a supported catalyst as the working electrode, a graphite rod as the counter electrode, a standard hydrogen electrode as the reference electrode, and 1M KOH solution as the electrolyte. The catalyst was activated and stabilized using cyclic voltammetry, and its OER performance was evaluated using linear sweep voltammetry.

[0073] The electrochemical testing experiment used the Shanghai Chenhua 760E electrochemical workstation.

[0074] Before testing, N2 was bubbled through the electrolyte for approximately 30 minutes to saturate it. Then, the three-electrode test system was assembled, with the voltage range set at 0–1.2V (vs. RHE). CV scans were performed for 20 cycles at scan rates of 100mV / s and 50mV / s to ensure complete sample activation and exposure of active sites. LSV testing was then conducted at 1.2–1.8V. The resistivity of the materials was determined by AC impedance spectroscopy to analyze and compare the kinetic activity of different materials.

[0075] Test conditions: 10mV disturbance near the test voltage, frequency range of 100kHz to 1Hz.

[0076] Example 1

[0077] NiSO4 (AR, 8 mmol), VOSO4 (AR, 2 mmol), and deionized water (30 mL) were mixed and stirred for 10 minutes. Then, 10 mL of KOH (AR) solution (1 mol / L) was added dropwise, and stirring was continued for another 10 minutes. Subsequently, the mixture was placed in a Teflon pressure reactor and hydrothermally crystallized at 120 °C for 24 hours. Finally, the solution was filtered with deionized water, and the recovered solid was vacuum dried overnight to obtain the NiV precursor. The synthesized NiV precursor was then subjected to hydrothermal treatment in 10 wt% H2 / Ar at 5 °C·min. -1 The heating rate was increased to 370℃, and calcined for 2.5 hours. Then dried for later use.

[0078] Scanning electron microscope, such as Figure 1 As shown, the particle size is approximately 20–50 nm.

[0079] The Ni-S / Ni3V composite catalyst was ground. 10 mg of the catalyst was weighed and added to 1 mL of isopropanol and 1 mL of Nafion, and ultrasonically dispersed for 30 min. Five 5 μL portions of the dispersion were added dropwise to a rotating disk electrode for testing its oxygen evolution performance in water electrolysis. A three-electrode system was constructed using the catalyst-supported rotating disk electrode as the working electrode, a graphite rod as the counter electrode, a standard hydrogen electrode as the reference electrode, and 1 M KOH solution as the electrolyte. The catalyst was activated and stabilized using cyclic voltammetry, and its OER performance was evaluated using linear sweep voltammetry.

[0080] The electrochemical testing experiment used the Shanghai Chenhua 760E electrochemical workstation.

[0081] Before testing, N2 was bubbled through the electrolyte for approximately 30 minutes to saturate it. Then, the three-electrode testing system was assembled, with the voltage range set at 0–1.2V (vs. RHE). CV scans were performed for 20 cycles at scan rates of 100mV / s and 50mV / s respectively to ensure complete sample activation and exposure of active sites. LSV testing was then conducted at 1.2–1.8V.

[0082] Test results are as follows Figure 5 As shown, at a current density of 10 mA / cm² 2 At this time, the oxygen evolution overpotential is 278 mV. At a current density of 100 mA / cm², 2 At that time, the oxygen evolution overpotential was 350 mV. The Tafel slope was 89 mV / dec.

[0083] Example 2

[0084] The procedure was carried out according to Example 1, except that NiSO4 (AR, 8 mmol), VOSO4 (AR, 1 mmol) and deionized water (30 mL) were mixed and stirred for 10 minutes.

[0085] Scanning electron microscope, such as Figure 7 As shown, the particle size is approximately 30–60 nm.

[0086] At a current density of 10 mA / cm 2 At that time, the oxygen evolution overpotential was 285mV.

[0087] Example 3

[0088] The method was carried out according to Example 1, except that NiSO4 (AR, 8 mmol), VOSO4 (AR, 1.2 mmol) and deionized water (30 mL) were mixed and stirred for 10 minutes.

[0089] The particle size of the product is approximately 40–70 nm.

[0090] At a current density of 10 mA / cm 2 At that time, the oxygen evolution overpotential was 282mV.

[0091] Example 4

[0092] The method was carried out according to Example 1, except that NiSO4 (AR, 8 mmol), VOSO4 (AR, 1.8 mmol) and deionized water (30 mL) were mixed and stirred for 10 minutes.

[0093] The particle size is approximately 30–80 nm.

[0094] At a current density of 10 mA / cm 2At that time, the oxygen evolution overpotential was 280mV.

[0095] Comparative Example 1

[0096] The procedure was carried out according to Example 1, except that Ni(NO3)2 (AR, 8 mmol) and Na3VO4 (AR, 2 mmol) were mixed with 30 mL of deionized water and stirred for 10 minutes.

[0097] At a current density of 10 mA / cm 2 At that time, the oxygen evolution overpotential was 381mV.

[0098] Comparative Example 2

[0099] The procedure was carried out according to Example 1, except that NiSO4 (AR, 8 mmol) and deionized water (30 mL) were mixed and stirred for 10 minutes.

[0100] At a current density of 10 mA / cm 2 At that time, the oxygen evolution overpotential was 370mV.

[0101] Comparative Example 3

[0102] The method was carried out according to Example 1, except that NiSO4 (AR, 8 mmol), VOSO4 (AR, 0.5 mmol) and deionized water (30 mL) were mixed and stirred for 10 minutes.

[0103] The particle size of the product is approximately 60–120 nm.

[0104] At a current density of 10 mA / cm 2 At that time, the oxygen evolution overpotential was 324mV.

[0105] Comparative Example 4

[0106] The method was carried out according to Example 1, except that NiSO4 (AR, 8 mmol), VOSO4 (AR, 0.2 mmol) and deionized water (30 mL) were mixed and stirred for 10 minutes.

[0107] The particle size of the product is approximately 60–120 nm.

[0108] At a current density of 10 mA / cm 2 At that time, the oxygen evolution overpotential was 364mV.

[0109] Comparative Example 5

[0110] The procedure was carried out according to Example 1, except that NiSO4 (AR, 8 mmol), VOSO4 (AR, 8 mmol) and deionized water (30 mL) were mixed and stirred for 10 minutes.

[0111] The particle size of the product is approximately 50–110 nm.

[0112] At a current density of 10 mA / cm 2 At that time, the oxygen evolution overpotential was 359mV.

[0113] Comparative Example 6

[0114] Commercial IrO2 was used as the oxygen evolution catalyst. Electrode solutions were prepared using the same method and coated onto the surface of a disk electrode for electrochemical performance testing.

[0115] At 10mA / cm 2 At the current density, the oxygen evolution overpotential of IrO2 is about 350mV.

[0116] The present invention has been described in detail above with reference to specific embodiments and exemplary examples; however, these descriptions should not be construed as limiting the present invention. Those skilled in the art will understand that various equivalent substitutions, modifications, or improvements can be made to the technical solutions and embodiments of the present invention without departing from the spirit and scope of the invention, and all such modifications and improvements fall within the scope of the present invention. The scope of protection of the present invention is defined by the appended claims.

[0117] All publications, patent applications, patents, and other references mentioned in this specification are incorporated herein by reference. Unless otherwise defined, all technical and scientific terms used in this specification have the meanings commonly understood by those skilled in the art. In case of conflict, the definitions in this specification shall prevail.

[0118] When this specification uses the prefixes “known to those skilled in the art,” “prior art,” or similar terms to derive materials, substances, methods, steps, apparatus, or components, the objects derived from such prefixes cover those commonly used in the art at the time of this application’s filing, but also include those that are not currently commonly used but will become generally recognized in the art as suitable for similar purposes.

[0119] In the context of this specification, except where expressly stated otherwise, any matters or issues not mentioned shall apply directly to those known in the art without any modification.

Claims

1. A nickel-vanadium-based composite catalyst comprising a Ni-S compound and Ni3V.

2. The nickel-vanadium based composite catalyst according to claim 1, characterized in that: The molar ratio of Ni3V to Ni-S compound is (2-10):1, preferably (2-5):

1.

3. The nickel-vanadium based composite catalyst according to claim 1, characterized in that: The size of the nickel-vanadium-based composite catalyst is 20–100 nm, preferably 20–60 nm.

4. A method for preparing a nickel-vanadium-based composite catalyst, preferably used to prepare the nickel-vanadium-based composite catalyst according to any one of claims 1 to 3, comprising mixing a sulfur-containing nickel source and a sulfur-containing vanadium source with water, adding an alkaline solution, performing hydrothermal crystallization to obtain a nickel-vanadium-based precursor, and finally calcining it in an inert gas / H2 atmosphere.

5. The preparation method according to claim 4, characterized in that: The sulfur-containing nickel source is selected from nickel sulfate; and / or, The sulfur-containing vanadium source is selected from vanadium oxysulfate; and / or, The alkaline solution is selected from at least one of potassium hydroxide solution, sodium hydroxide solution, and ammonia water.

6. The preparation method according to claim 4, characterized in that: The molar ratio of nickel source to vanadium source is (4–8):1; and / or, The molar ratio of alkaline solution to vanadium source is (4–10):1; and / or, The concentration of the alkali solution is 1–2.5 M.

7. The preparation method according to claim 4, characterized in that: The hydrothermal crystallization temperature is 100–180℃ and the time is 20–28h; preferably, the hydrothermal crystallization temperature is 100–160℃ and the time is 23–26h.

8. The preparation method according to claim 4, characterized in that: The heating rate for calcination is 4–8 °C / min, preferably 4–6 °C / min; and / or, The calcination temperature is 360–580℃ and the time is 2–4 hours; preferably, the calcination temperature is 370–550℃ and the time is 2–3 hours.

9. The application of the nickel-vanadium-based composite catalyst according to any one of claims 1 to 3 or the nickel-vanadium-based composite catalyst obtained by the preparation method according to any one of claims 2 to 8 in the electrocatalytic oxygen evolution process.

10. The application according to claim 9, characterized in that: The nickel-vanadium-based composite catalyst is used in the alkaline membrane water electrolysis process.

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