Preparation method of electrolytic water catalyst suitable for full pH range

Abstract

The application relates to a preparation method of an electrolytic water catalyst suitable for a full pH range, which comprises the following steps: (S1) dissolving 1,1'-ferrocene dicarboxylic acid in an organic solvent to form solution A, dissolving a ferrous salt and a tungsten salt in water to form solution B, uniformly mixing solution A and solution B, adding foamed nickel, and carrying out a hydrothermal reaction of the mixed solution in a reaction kettle to obtain tungsten-doped ferrocene metal organic framework nanosheets; (S2) mixing the tungsten-doped ferrocene metal organic framework nanosheets obtained in step (S1) and a nitrogen source, and sintering under an inert atmosphere to obtain the electrolytic water catalyst suitable for the full pH range. The application uses the abundant transition metal tungsten as a dopant, forms a nanoelectrode material with the cost-effective transition metal iron-based nitride, and further obtains a catalyst which can be used for hydrogen evolution reaction, oxygen evolution reaction and overall water splitting and has high catalytic activity and high stability in different pH electrolytes.

Description

Technical Field

[0001] This invention belongs to the field of water electrolysis catalyst technology, specifically relating to a method for preparing a water electrolysis catalyst applicable across the entire pH range. Background Technology

[0002] Hydrogen energy, as a green, clean, and sustainable new energy source, has attracted widespread attention due to its zero carbon emissions, safety, non-toxicity, and high energy density. Electrochemical water splitting for hydrogen production is an effective way to address energy shortages and overcome time and space limitations. Electrochemical water splitting involves hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) at the cathode and anode, respectively, ideally requiring only a potential of 1.23V to achieve water splitting. Currently, the most effective catalysts for HER and OER are noble metal catalysts such as Pt / C and RuO2 / IrO2, respectively. However, the high cost, low abundance, and scarcity of these noble metal catalysts severely limit their widespread application.

[0003] Most reported high-performance electrocatalysts only achieve high activity in acidic or alkaline electrolytes. Considering cost and efficiency, constructing multifunctional electrocatalysts suitable for electrolytes with different pH values ​​is of significant technical importance. Therefore, developing transition metal-based catalysts with high activity, high stability, and low cost over a wide pH range remains a key research focus.

[0004] Transition metal nitrides (TMNs) are considered promising electrode materials for efficient hydrogen evolution reaction (HER), oxygen evolution reaction (OER), and overall water splitting due to their unique noble metal-like structure, high conductivity, corrosion resistance, broad pH stability, and structural modifiability. Iron-based nitride catalysts are considered ideal electrocatalysts due to their abundant reserves, low cost, and high catalytic activity. Fe has been reported in the literature. x N is a good OER catalyst (DING J, et al. N-doped mesoporous FeN). x / carbon as ORR and OER bifunctional electrocatalyst for rechargeable zinc-air batteries[J]. Electrochimica Acta, 2019, 296: 653-661). Due to insufficient MH / M-OH binding strength, the catalytic performance of iron-based nitrides alone is not ideal. Other transition metal nitrides, such as Ta3N5 and MoN, have shown good HER catalytic performance. However, there is currently no catalyst that can exhibit excellent OER and HER catalytic activity under all pH conditions.

[0005] CN111206271A discloses a self-supporting metal-doped iron nitride electrode. The process involves cleaning an iron foil, using it as the anode, and a platinum sheet as the cathode. An ethylene glycol solution containing 0.1 M NH4F and 1 M H2O is used as the electrolyte to electrolyze and obtain porous iron oxide with an iron-based conductive substrate. Then, using the porous iron oxide as the cathode and the platinum sheet as the anode, electrodeposition is performed in an electrolyte containing 0.9-1.2 M metal salts. The pH is adjusted with boric acid to obtain metal-doped porous iron oxide. Finally, the metal-doped porous iron oxide undergoes a nitriding reaction in a CVD tube furnace under an ammonia atmosphere. After cooling, the self-supporting metal-doped iron nitride electrode is obtained. This patented process is complex and the operation is complicated, making it unsuitable for large-scale industrial production. Furthermore, ammonia is a flammable and explosive gas with an irritating odor and toxicity, posing potential safety hazards when used as a nitrogen source in the reaction. Summary of the Invention

[0006] To address the shortcomings of existing technologies where transition metal nitrides as water electrolysis catalysts cannot be used across the entire pH range and where catalytic activity and stability need further improvement, this invention utilizes abundant transition metal tungsten as a dopant to form nanoelectrode materials with cost-effective transition metal iron-based nitrides. This results in a catalyst with high catalytic activity and high stability in electrolytes of different pH values, suitable for hydrogen evolution reaction, oxygen evolution reaction, and overall water splitting.

[0007] The present invention achieves the above objectives through the following technical solutions:

[0008] A method for preparing a water electrolysis catalyst suitable for the entire pH range includes the following steps:

[0009] (S1) 1,1'-ferrocene dicarboxylic acid is dissolved in an organic solvent to form solution A, and iron salt and tungsten salt are dissolved in water to form solution B. Solution A and solution B are mixed evenly, and nickel foam is added. The mixed solution is subjected to hydrothermal reaction in a reactor to obtain tungsten-doped ferrocene-based metal-organic framework nanosheets.

[0010] (S2) The tungsten-doped ferrocene-based metal-organic framework nanosheets obtained in step (S1) are mixed with a nitrogen source and sintered under an inert atmosphere to obtain the water electrolysis catalyst applicable to the entire pH range.

[0011] The water electrolysis catalyst suitable for the entire pH range obtained in this invention is named W-Fe3N@NC@NF, where W-Fe3N represents tungsten-doped iron nitride, NC represents N-doped carbon layer, and NF represents nickel foam support.

[0012] This invention utilizes ferrocene dicarboxylic acid (FCA) as a precursor for metal-organic frameworks (MOFs). The conformation of FCA makes it an attractive ligand for constructing MOFs with various structural features. This invention employs a one-pot hydrothermal process and a nitridation step to obtain a tungsten-doped transition metal iron-based nitride—W-Fe3N@NC@NF—supported on a nickel foam substrate. The organic components in the FCA precursor can form a nitrogen-doped carbon layer, which can both stabilize the catalyst and prevent aggregation, and also serve as an electron collecting and transport layer. Furthermore, during the reaction, the carbon in the nitrogen-doped carbon layer can form activated carbon (C2). * -Csp 3 and C * -C sp 2 This process can promote electron transfer, enhance reactivity, and accelerate the reaction process. Furthermore, ferrocene dicarboxylic acid is a representative transition metal complex with a sandwich structure. Due to the aromaticity of the two cyclopentadienyl rings, it exhibits excellent chemical stability as well as significant redox and magnetic properties. After nitriding, the metal-organic framework structure can serve as a supporting framework, effectively preventing particle aggregation, avoiding activity decay, and enhancing stability. In 1.0 M PBS and 1.0 M KOH solution, the HER reaction of W-Fe3N@NC@NF maintained a current density above 90% after 72 hours of continuous operation.

[0013] Compared to pure-phase iron nitride (Fe3N@NC@NF) without W doping, the W doping-induced catalyst underwent electron transfer and charge redistribution, resulting in the production of some Fe with higher oxidation states. 4+ Species. Fe 4+ Species, as high-valence metal active sites, are highly active centers in the OER process and can exhibit better OER activity.

[0014] The incorporation of W as a dopant enhances the structural stability of the catalyst, significantly improving its HER stability under all pH conditions (alkaline, acidic, and neutral) and OER stability in alkaline media. The catalyst exhibits a slow decay in current density after prolonged operation.

[0015] Further, in step (S1), the iron salt is selected from at least one of trivalent iron halides, nitrates, and sulfates; the tungsten salt is selected from at least one of sodium tungstate, tungsten hexachloride, tungsten pentachloride, calcium tungstate, and tungsten carbonate; the organic solvent is selected from at least one of N,N-dimethylformamide, formamide, diethylformamide, and dimethylacetamide; even further, the concentration of 1,1'-ferrocene dicarboxylic acid in solution A is 0.05-0.10 mol / L, preferably 0.0625-0.08 mol / L; and the concentrations of iron salt (calculated as Fe) and tungsten salt (calculated as W) in solution B are 0.04-0.12 mol / L, preferably 0.05-0.08 mol / L.

[0016] Further, in step (S1), the molar ratio of 1,1'-ferrocene dicarboxylic acid, iron salt (calculated as Fe) and tungsten salt (calculated as W) is 1-2:0.3-1.2:0.3-1.2, preferably 1-2:1-1.2:1-1.2.

[0017] Furthermore, in step (S1), solution A and solution B are mixed under stirring conditions; the hydrothermal reaction conditions are 110-130℃ for 10-20h, preferably 120-125℃ for 12-15h.

[0018] Further, in step (S1), the nickel foam is cleaned by sequentially ultrasonically washing with 0.5-2M HCl, deionized water, and ethanol for 10-30 minutes. The purpose of cleaning is to remove surface impurities. The treated nickel foam is then transferred to a vacuum drying oven for later use. The amount of nickel foam used is 0.2-0.4 mmol of ferrocene diformate per 100 mg of nickel foam.

[0019] Further, in step (S2), the nitrogen source is selected from at least one of urea, melamine, imidazole, pyridine, thiazole, benzothiazole, and dibenzothiazole disulfide, and the ratio of nitrogen source to nickel foam is 1g: 400-600mg, preferably 1g: 450-500mg.

[0020] Further, in step (S2), the inert atmosphere is nitrogen and / or argon, and the sintering is performed by heating to 400-600°C at a heating rate of 2-5°C / min and holding for 2-5 hours, preferably heating to 450-500°C and holding for 2-3 hours.

[0021] Compared with the prior art, the present invention has achieved the following technical advancements:

[0022] I. This invention synthesizes and prepares a catalyst for water electrolysis that can operate under all pH conditions through simple steps. The catalyst obtained by this invention has high catalytic activity, is stable, has a long lifespan, and can work for a long time while maintaining high catalytic activity, providing the possibility of industrial practicality for hydrogen production by water electrolysis.

[0023] II. This invention uses non-precious metal tungsten as a dopant to obtain a tungsten-doped transition metal iron-based nitride hybrid nanosheet catalyst. Compared with precious metal catalysts, this significantly reduces material costs.

[0024] III. The hybrid catalyst material of this invention exhibits a rough yet ordered nanosheet array structure. Compared to pure Fe3N@NC@NF, the thickness of the nanosheets can be adjusted by regulating the amount of tungsten doping. The W-Fe3N@NC@NF nanosheets are thinner, resulting in a larger contact area with the electrolyte during the reaction. XRD results show that the introduction of tungsten did not alter the crystal structure of the iron-based nitrides. However, TEM results show that the Fe3N grain size in W-Fe3N@NC@NF is smaller than that in Fe3N@NC@NF. The smaller grain size increases the specific surface area, exposing more reaction sites.

[0025] IV. This invention utilizes a simple strategy to directly and in-situ form iron ions (Fe2+) with a higher oxidation state after incorporating metallic tungsten. 4+ ) species. The doping of W induces changes in the electronic structure of the W-Fe3N@NC@NF catalyst, producing some high-valence iron-Fe. 4+ As highly active species in the OER process, these species can further enhance the catalytic activity.

[0026] V. The hybrid catalyst formed by the present invention, thanks to the incorporation of W, effectively improves its stability in the catalytic reaction and exhibits excellent long-cycle stability during the catalytic process.

[0027] VI. This invention utilizes ferrocene dicarboxylic acid as an organic ligand. After nitriding, the nitrogen-doped carbon layer derived from the organic component in the ferrocene structure can not only stabilize the catalyst and prevent aggregation, but also serve as an electron collection and transport layer. Furthermore, it can act as an active substance (C*-Csp) during the reaction process. 3 C*-C sp 2 It improves electron transport efficiency and enhances catalytic performance. Attached Figure Description

[0028] Figure 1 Here is a SEM image of the catalyst obtained in Example 1;

[0029] Figure 2 The image shows the SEM image of the catalyst obtained in Comparative Example 1.

[0030] Figure 3 The image shows a TEM image of the catalyst obtained in Example 1.

[0031] Figure 4 The XRD pattern of the catalyst obtained in Example 1 is shown below.

[0032] Figure 5 XPS plot (A) of the catalyst obtained in Example 1 and Fe 2p plot (B) of the catalyst obtained in Example 1;

[0033] Figure 6 The EDS spectrum of the catalyst obtained in Example 1 is shown below.

[0034] Figure 7 The above are C1s XPS images of the catalyst obtained in Example 1 before and after the reaction.

[0035] Figure 8 The polarization curves (A) and electrochemical impedance curves (B) of the hydrogen evolution reaction (HER) in 0.5 M H2SO4 for the catalysts obtained in Example 1 and Comparative Example 1 are shown.

[0036] Figure 9 The polarization curves (A) and electrochemical impedance curves (B) of the hydrogen evolution reaction (HER) of the catalysts obtained in Example 1 and Comparative Example 1 in 1.0 M PBS solution are shown.

[0037] Figure 10 The polarization curves (A) and electrochemical impedance curves (B) of the hydrogen evolution reaction (HER) of the catalysts obtained in Example 1 and Comparative Example 1 in 1.0 M KOH solution are shown.

[0038] Figure 11 The polarization curves (A) and electrochemical impedance curves (B) of the oxygen evolution reaction (OER) in 1.0 M KOH solution are shown for the catalysts obtained in Example 1 and Comparative Example 1.

[0039] Figure 12 The stability of the catalysts obtained in Example 1 and Comparative Example 1 in the hydrogen evolution reaction (HER) in 0.5 M H2SO4 solution was tested.

[0040] Figure 13 The stability of the catalysts obtained in Example 1 and Comparative Example 1 in the hydrogen evolution reaction (HER) in 1.0 M PBS solution was tested.

[0041] Figure 14 The stability of the catalysts obtained in Example 1 and Comparative Example 1 in the hydrogen evolution reaction (HER) in 1.0 M KOH solution was tested.

[0042] Figure 15 The stability of the catalysts obtained in Example 1 and Comparative Example 1 in the oxygen evolution reaction (OER) in 1.0 M KOH solution;

[0043] Figure 16 The image shows the polarization curve of the catalyst obtained in Example 1 during the electrochemical decomposition of water in 1.0 M KOH solution. Detailed Implementation

[0044] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be described in detail below. The following embodiments are provided to better understand this invention, but do not limit the invention. Unless otherwise specified, the experimental methods in the following embodiments are conventional methods.

[0045] Example 1

[0046] (S1) Before use, the nickel foam (1cm×2cm) was pretreated by ultrasonically washing with 1.0M HCl, deionized water, and ethanol for 10 minutes to remove surface impurities. The treated nickel foam was then transferred to a vacuum drying oven for drying. Tungsten-doped ferrocene-based metal-organic framework compounds were obtained using a hydrothermal reaction. The specific steps are as follows: 0.5 mmol of 1,1'-ferrocene dicarboxylic acid was dissolved in 8 mL of N,N-dimethylformamide to form solution A; 0.25 mmol of FeCl3·6H2O and 0.25 mmol of Na2WO4·2H2O were dissolved in 4 mL of deionized water by ultrasonic dissolution to form solution B. The two solutions were then rapidly mixed thoroughly. Two pieces of nickel foam (approximately 225 mg) were immersed in the solution. The mixed solution was poured into a 50 mL stainless steel reactor, the reactor was sealed, and heated at 125°C for 12 hours. After the reaction vessel has cooled to room temperature, the sample is washed with deionized water and ethanol respectively, and then vacuum dried at 60°C overnight to successfully prepare tungsten-doped ferrocene-based metal-organic framework nanosheets.

[0047] (S2) Then, the tungsten-doped ferrocene-based metal-organic framework nanosheets obtained in step (S1) and 0.5 g of urea were placed in a quartz tube of a tubular furnace and incubated at 2 °C for 1 minute under an Ar atmosphere. -1 The temperature was increased to 450℃ at a rising rate and held for 120 min. After cooling to room temperature, the target product, namely a water electrolysis catalyst suitable for the entire pH range, was obtained and named W-Fe3N@NC@NF, where W-Fe3N represents tungsten-doped iron nitride, NC represents N-doped carbon layer, and NF represents nickel foam support.

[0048] Figure 1 This is an SEM image of the catalyst obtained in Example 1. Figure 2The image shows a SEM image of the catalyst obtained in Comparative Example 1. It can be seen that the thickness of the W-Fe3N@NC@NF nanosheets is approximately 35–80 nm, while the thickness of the Fe3N@NC@NF nanosheets is approximately 500–650 nm. This indicates that W doping effectively controls the morphology of the nanosheets, resulting in thinner nanosheets after W doping. Figure 3 The image shows a TEM image of the catalyst obtained in Example 1. It can be seen that the Fe3N particles are uniformly distributed on the nitrogen-doped carbon support.

[0049] Figure 4 This is the XRD pattern of the catalyst obtained in Example 1. It can be seen that the obtained W-Fe3N@NC@NF is composed of Fe3N (JCPDS No. 49-1663), and the doping of W did not change the crystal structure of Fe3N. Due to the W doping, the XRD pattern shows a very small shift.

[0050] Figure 5 The image shows the XPS plot of the catalyst obtained in Example 1, which reveals the presence of Fe, W, C, and O elements.

[0051] Figure 6 The image shows the EDS spectrum of the catalyst obtained in Example 1. It can be seen that the Fe content is stronger than that of W, and the ratio is approximately Fe:W = 25:1.

[0052] Figure 7 The images show the C1s XPS plots of the catalyst obtained in Example 1 before and after the reaction; after the HER and OER reactions, C*-Csp appears. 3 and C*-C sp 2 The characteristic peak signal is the excited state of carbon in the electrochemical process, which can promote electron transfer and enhance catalytic performance.

[0053] Example 2

[0054] The other conditions are the same as in Example 1, except that the ratio of FeCl3·6H2O to Na2WO4·2H2O is changed to 5:1 (the total amount is kept at 0.5 mmol).

[0055] Example 3

[0056] The other conditions are the same as in Example 1, except that the ratio of FeCl3·6H2O to Na2WO4·2H2O is changed to 1:5 (the total amount is kept at 0.5 mmol).

[0057] Example 4

[0058] The other conditions are the same as in Example 1, except that urea is replaced with an equal mass of melamine.

[0059] Example 5

[0060] The other conditions are the same as in Example 1, except that urea is replaced with an equal mass of thiazole.

[0061] Comparative Example 1

[0062] The other conditions are the same as in Example 1, except that Na2WO4·2H2O is not added, i.e., W doping is not performed. It is named Fe3N@NC@NF.

[0063] Comparative Example 2

[0064] The other conditions are the same as in Example 1, except that Na2WO4·2H2O is replaced with an equal amount of Na2MoO4·2H2O.

[0065] Comparative Example 3

[0066] The other conditions are the same as in Example 1, except that 1,1'-ferrocene dicarboxylic acid is replaced with an equal amount of ferric citrate.

[0067] Application examples

[0068] The electrochemical performance of the materials was evaluated using a three-electrode system on an electrochemical workstation. The obtained materials were used directly as the working electrode without further processing, with a graphite rod (HER) or platinum wire (OER) as the counter electrode and a saturated calomel electrode as the reference electrode. Electrolysis was performed in electrolytes of 0.5 M H₂SO₄ (pH=0), 1.0 M PBS (pH=7), and 1.0 M KOH (pH=14) at a rate of 5 mV / s. -1 With a scan rate of 5 mVs and a resistance compensation of 90%, the HER polarization curves were obtained using linear sweep voltammetry (LSV). The method was performed in a 1.0 M KOH electrolyte. -1 At a scan rate of 10, with 90% resistance compensation, the OER polarization curve was obtained using the linear sweep voltammetry (LSV) method. -1 ~10 5 Electrochemical impedance spectroscopy (EIS) was studied in the frequency range of Hz. The stability of the catalyst was determined by chronoamperometry.

[0069] In the overall water splitting (OWS) test, the synthesized catalyst material was used as both the cathode and anode in a 1.0 M KOH electrolyte.

[0070] Figure 8 These are the polarization curves of the hydrogen evolution reaction (HER) of the catalysts obtained in Example 1 and Comparative Example 1 in 0.5 M H2SO4. Figure 8 Electrochemical impedance spectroscopy (EIR) curves of HER in the hydrogen evolution reaction at 0.5 M H₂SO₄ (A) and (B) Figure 8 (B).

[0071] Figure 9 These are the polarization curves of the hydrogen evolution reaction (HER) of the catalysts obtained in Example 1 and Comparative Example 1 in 1.0 M PBS solution. Figure 9 Electrochemical impedance spectroscopy curves of HER (A) and hydrogen evolution reaction in 1.0 M PBS solution ( Figure 9 (B).

[0072] Figure 10 These are the polarization curves of the hydrogen evolution reaction (HER) of the catalysts obtained in Example 1 and Comparative Example 1 in 1.0 M KOH solution. Figure 10 Electrochemical impedance spectroscopy curves of HER (A) and the hydrogen evolution reaction in 1.0 M KOH solution. Figure 10 (B).

[0073] Figure 11 These are the polarization curves of the oxygen evolution reaction (OER) of the catalysts obtained in Example 1 and Comparative Example 1 in 1.0 M KOH solution. Figure 11 Electrochemical impedance spectroscopy curves of the oxygen evolution reaction (OER) in 1.0 M KOH solution (A) and OER in 1.0 M KOH solution. Figure 11 (B).

[0074] Figure 12 The stability of the catalysts obtained in Example 1 and Comparative Example 1 in the hydrogen evolution reaction (HER) in 0.5 M H2SO4 solution.

[0075] Figure 13 The stability of the catalysts obtained in Example 1 and Comparative Example 1 in the hydrogen evolution reaction (HER) in 1.0 M PBS solution was measured.

[0076] Figure 14 The stability of the catalysts obtained in Example 1 and Comparative Example 1 in the hydrogen evolution reaction (HER) in 1.0 M KOH solution.

[0077] Figure 15 The stability of the catalysts obtained in Example 1 and Comparative Example 1 in the oxygen evolution reaction (OER) in 1.0 M KOH solution.

[0078] Figure 16 The image shows the polarization curve of the catalyst obtained in Example 1 during the electrochemical complete water splitting in 1.0 M KOH solution.

[0079] The electrochemical performance test results of Example 1 and Comparative Example 1 show that Example 1's HER performance across the entire pH range and its OER performance under alkaline conditions are significantly better than those of Comparative Example 1. Figures 8-11 ).

[0080] The stability test results from Example 1 and Comparative Example 1 show that W doping effectively improves catalyst durability. Figures 12-15 ).

[0081] In total dissolved water ( Figure 16 Example 1 requires only a 1.47V battery voltage to generate 10mA cm. -2 The current density required for Comparative Example 1 is 1.57V, while Comparative Example 1 requires 1.57V to reach 10mA cm⁻¹. -2 .

[0082] The electrochemical performance of the catalysts obtained in the above examples and comparative examples is listed below.

[0083] Table 1 Electrochemical performance of catalysts

[0084]

[0085] Table 2. Stability properties of the catalysts

[0086]

[0087]

[0088] The performance comparison between the electrocatalyst provided by this invention and existing catalysts is as follows:

[0089] Table 3 Comparison of HER performance of the catalyst and other iron-based catalysts in 0.5 M H2SO4 solution

[0090] Ce-FeP 51 76 <![CDATA[P-Fe2N / rGO]]> 64 48 <![CDATA[Pt5 / Fe2O3]]> 15 25 <![CDATA[Pd / NiFeO x ]]> 46 76 FeP@CoP 40 34 <![CDATA[FeN4 / NF / EG]]> 294 129 Fe-N-WC 98 90 <![CDATA[NiFe2O4@N-rGO-CC]]> 188 218 <![CDATA[MoS2@FePS3]]> 168 107 <![CDATA[Fe 0.4 What 0.6 -NCNTs]]> 50 40 Example 1 67 85 Comparative Example 1 115 142

[0091] Table 4. Comparison of HER performance of the catalyst and other iron-based catalysts in 1.0 M PBS solution.

[0092] <![CDATA[Pd / NiFeO x ]]> 75 103.1 FeP@CoP 66 83 pFe / FeP 250 63 <![CDATA[Fe 0.4 What 0.6 -NCNTs]]> 202 - <![CDATA[P-Fe3O4@3DG]]> 295.4 234.6 CoP@3DOM-FeP 71.1 76 <![CDATA[Fe-Ni3S2@FeNi3]]> 83 73 CoP-FeP 134.2 50.1 <![CDATA[FeMo@CoNi-OH / Ni3S2]]> 177 119.3 Example 1 174 195.29 Comparative Example 1 208 270.08

[0093] Table 5. Comparison of HER performance of the catalyst and other iron-based catalysts in 1.0 M KOH solution.

[0094]

[0095]

[0096] Table 6. Comparison of OER performance of the catalyst and other iron-based catalysts in 1.0 M KOH solution.

[0097] <![CDATA[C / O-FeNi / FeF2]]> <![CDATA[250(10mA cm -2 )]]> 52 <![CDATA[FeNi3-N]]> <![CDATA[222(10mA cm -2 )]]> 41.53 <![CDATA[Fe3N@Ni2Co-LDHs]]> <![CDATA[240(10mA cm -2 )]]> 38.9 <![CDATA[Fe2P@CoMnP4 / NF]]> <![CDATA[249(10mA cm -2 )]]> 52 <![CDATA[Fe / Fe3C-A@CNT]]> <![CDATA[292(10mA cm -2 )]]> 29 <![CDATA[Cu2S / CoFeCuOOH]]> <![CDATA[170(10mA cm -2 )]]> 41 CoFe-P-1 <![CDATA[258(10mA cm -2 )]]> 70.1 <![CDATA[FeS2 / CoNiSe2]]> <![CDATA[230(10mA cm -2 )]]> 54 <![CDATA[γ-Fe2O3@FeS2@C]]> <![CDATA[268(10mA cm -2 )]]> 54 <![CDATA[FeNi3N-Ni3S2]]> <![CDATA[230(10mA cm -2 )]]> 38 <![CDATA[Ni2Fe2N / Ni3Fe]]> <![CDATA[251(10mA cm -2 )]]> 35 <![CDATA[Ni2Co2Fe1-P]]> <![CDATA[275(10mA cm -2 )]]> 39 <![CDATA[Fe3N@Ni2Co-LDHs]]> <![CDATA[240(10mA cm -2 )]]> 38.9 Example 1 <![CDATA[239(20mA cm -2 )]]> 61.6 Comparative Example 1 <![CDATA[370(20mA cm -2 )]]> 109.1

Claims

1. A method for preparing a water electrolysis catalyst suitable for the entire pH range, characterized in that, Includes the following steps: (S1) 1,1'-ferrocene dicarboxylic acid is dissolved in an organic solvent to form solution A, and iron salt and tungsten salt are dissolved in water to form solution B. Solution A and solution B are mixed evenly, and nickel foam is added. The mixed solution is subjected to hydrothermal reaction in a reactor to obtain tungsten-doped ferrocene-based metal-organic framework nanosheets. The concentration of 1,1'-ferrocene dicarboxylic acid in solution A is 0.05-0.10 mol / L; the concentration of iron salt (calculated as Fe) and tungsten salt (calculated as W) in solution B is 0.04-0.12 mol / L; the molar ratio of 1,1'-ferrocene dicarboxylic acid, iron salt (calculated as Fe), and tungsten salt (calculated as W) is 1-2:0.3-1.2:0.3-1.

2. (S2) The tungsten-doped ferrocene-based metal-organic framework nanosheets obtained in step (S1) are mixed with a nitrogen source and sintered under an inert atmosphere to obtain the water electrolysis catalyst applicable to the entire pH range.

2. The preparation method according to claim 1, characterized in that, In step (S1), the iron salt is selected from at least one of trivalent iron halides, nitrates, and sulfates; the tungsten salt is selected from at least one of sodium tungstate, tungsten hexachloride, tungsten pentachloride, calcium tungstate, and tungsten carbonate; and the organic solvent is selected from at least one of N,N-dimethylformamide, formamide, diethylformamide, and dimethylacetamide.

3. The preparation method according to claim 1, characterized in that, The concentration of 1,1'-ferrocene dicarboxylic acid in solution A is 0.0625-0.08 mol / L; the concentrations of iron salt (calculated as Fe) and tungsten salt (calculated as W) in solution B are 0.05-0.08 mol / L.

4. The preparation method according to claim 1, characterized in that, In step (S1), the molar ratio of 1,1'-ferrocene dicarboxylic acid, iron salt (calculated as Fe), and tungsten salt (calculated as W) is 1-2:1-1.2:1-1.

2.

5. The preparation method according to claim 1, characterized in that, In step (S1), the hydrothermal reaction conditions are 110-130℃ for 10-20h.

6. The preparation method according to claim 1, characterized in that, In step (S1), the hydrothermal reaction conditions are 120-125℃ for 12-15 hours.

7. The preparation method according to claim 1, characterized in that, In step (S1), the nickel foam is cleaned by sequentially ultrasonically washing with 0.5-2 M HCl, deionized water, and ethanol for 10-30 min. The treated nickel foam is then transferred to a vacuum drying oven for later use.

8. The preparation method according to claim 7, characterized in that, The dosage of nickel foam is 0.2-0.4 mmol of 1,1'-ferrocene dicarboxylic acid per 100 mg of nickel foam.

9. The preparation method according to claim 1, characterized in that, In step (S2), the nitrogen source is selected from at least one of urea, melamine, imidazole, pyridine, thiazole, benzothiazole, and dibenzothiazole disulfide, and the ratio of nitrogen source to nickel foam is 1g: 400-600mg.

10. The preparation method according to claim 1, characterized in that, In step (S2), the ratio of nitrogen source to nickel foam is 1g: 450-500mg.

11. The preparation method according to claim 1, characterized in that, In step (S2), the inert atmosphere is nitrogen and / or argon, and the sintering is carried out by heating to 400-600℃ at a heating rate of 2-5℃ / min and holding at that temperature for 2-5 h.

12. The preparation method according to claim 1, characterized in that, In step (S2), sintering is performed by heating to 450-500℃ at a heating rate of 2-5℃ / min and holding at that temperature for 2-3 hours.

13. A water electrolysis catalyst, characterized in that, It is prepared by the method described in any one of claims 1-12.

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