Preparation method of tungsten-induced sub-nano iridium oxide cluster electrocatalyst, electrocatalyst and application thereof

Abstract

The invention relates to a preparation method of a tungsten-induced sub-nano iridium oxide cluster electrocatalyst, which comprises the following steps: adding an iridium source, a tungsten source and graphene oxide into a mixed solvent composed of water and absolute ethyl alcohol to obtain a precursor solution; adjusting the pH value of the precursor solution to strong alkalinity, and then carrying out solvothermal reaction to obtain a reaction product; and drying a reaction product, and then carrying out high-temperature nitridation by adopting a chemical vapor deposition method to obtain the sub-nano iridium oxide cluster electrocatalyst. The catalyst has excellent oxygen evolution electrochemical performance, is high in catalytic activity, stable in performance, rich in active sites and uniform in distribution, and can effectively reduce the overpotential of oxygen evolution reaction and accelerate the reaction kinetic process.

Description

Technical Field

[0001] The invention belongs to the technical field of electrochemical catalysis, and particularly relates to a preparation method of a tungsten-induced sub-nanometer iridium oxygen cluster electrocatalyst, an electrocatalyst and applications thereof. Background Art

[0002] Oxygen evolution reaction (OER) is a key component of various renewable electrochemical technologies in the field of energy conversion. Anodic OER consists of complex proton-coupled four-electron transfer steps, which usually requires high energy to overcome the reaction barrier, which severely limits the overall efficiency of electrolytic water splitting. In recent years, iridium-based materials have been widely regarded as state-of-the-art OER electrocatalysts due to their excellent intrinsic activity. Among them, IrO x Nanoclusters have abundant active sites, electrophilic oxygen properties, and excellent corrosion resistance under acidic conditions, making them stand out among iridium-based electrocatalysts. x Nanoclusters show considerable difficulty in direct surface deprotonation of intermediates and have poor stability in high potential regions (>1.6 V), which seriously affects the OER catalytic performance. At the same time, as the particle size decreases, the surface energy increases rapidly, Ir atoms tend to aggregate strongly, and the grains further grow into larger crystals, which seriously impairs the electrochemical OER activity. Summary of the invention

[0003] The purpose of the present invention is to provide a preparation method of a tungsten-induced sub-nanometer iridium oxygen cluster electrocatalyst, an electrocatalyst and its application, so as to solve the technical problems of the existing preparation method in how to achieve rapid deprotonation of intermediates and over-oxidation of catalytic sites in high voltage areas;

[0004] In order to achieve the above object, the technical solution adopted by the present invention is:

[0005] A method for preparing a tungsten-induced sub-nanometer iridium-oxygen cluster electrocatalyst comprises the following steps:

[0006] S1. Adding an iridium source, a tungsten source, and graphene oxide to a mixed solvent consisting of deionized water and anhydrous ethanol to obtain a precursor solution; adjusting the pH value of the precursor solution to a strong alkaline state with a pH value of 9-11 using sodium hydroxide, and then performing a solvothermal reaction to obtain a reaction product;

[0007] S2. Dry the reaction product, and then use chemical vapor deposition to perform high-temperature nitridation to obtain a sub-nanometer iridium oxide cluster electrocatalyst.

[0008] Preferably, the percentage of iridium in the iridium source to the mass of graphene oxide is 2.5-10%; the percentage of tungsten in the tungsten source to the mass of graphene oxide is 2-12%.

[0009] Preferably, in step S1, graphene oxide is dispersed in a mixed solution of deionized water and anhydrous ethanol, and ultrasonically treated for 4 to 8 hours to obtain a graphene oxide suspension, wherein the concentration of the graphene oxide suspension is 2 mg / mL, and the volume ratio of deionized water to anhydrous ethanol is 1:1, and then an iridium source and a tungsten source are added to the graphene oxide suspension, and ultrasonicated for 1 to 4 hours to obtain a precursor solution.

[0010] Preferably, the mass volume ratio of the graphene oxide, deionized water and anhydrous ethanol is: 4 mg: 1 mL:: 1 mL.

[0011] Preferably, the iridium source is iridium trichloride; and the tungsten source is tungsten hexachloride.

[0012] Preferably, in step S1, the temperature of the solvent thermal reaction is 160-200° C., and the reaction time is 10-18 hours.

[0013] Preferably, in step S2, the drying process is freeze-drying process, and the freeze-drying process time is 2 to 15 hours.

[0014] Preferably, in step S2, the high-temperature nitridation using chemical vapor deposition method includes the following steps: nitridation is carried out in a mixed atmosphere of argon and ammonia, the reaction temperature is 600-1000°C, the reaction time is 1-3h, the argon flow rate is 100±50sccm, and the ammonia flow rate is 50±10sccm.

[0015] Another aspect of the present invention provides an electrocatalyst prepared by the preparation method as described above.

[0016] Another aspect of the present invention provides the use of the electrocatalyst described above as an electrocatalyst for generating oxygen through an acidic oxygen evolution reaction.

[0017] The present invention uses iridium trichloride (IrCl3) and tungsten hexachloride (WCl6) as iridium source and tungsten source respectively, ammonia (NH3) as nitrogen source, and adopts solvent thermal method and chemical vapor deposition (CVD) method to synthesize sub-nanometer iridium oxygen cluster electrocatalyst at high temperature. In a strongly alkaline solution, IrCl3 hydrolyzes and polycondenses to form [Ir(OH)6] with Ir-O oligomer structure. 3- The anion, WCl6, reacts with ethanol to generate tungsten oxide (W) with oxygen vacancies via non-hydrolytic conversion. 18 O 49 ), which can anchor the negatively charged [Ir(OH)6] 3- , [Ir(OH)6] 3-Anions are embedded in the oxygen vacancies of tungsten oxide formed by the conversion of WCl6 and loaded on graphene oxide. Due to the gradual increase of water molecules in the reaction system, the OWO structure can partially convert W=O and W-OH2 bonds, thereby inhibiting the crystal growth of tungsten oxide. Subsequently, under high-temperature nitridation conditions, W single atoms coupled with subnanometer-sized iridium oxygen clusters (IrOx) electrocatalysts connected by bridging oxygen are formed. The introduction of high-valent W single atoms (W-N3O1) as electron-rich groups effectively regulates the local electron distribution of IrOx, significantly improves the OER activity, and inhibits the over-oxidation of iridium.

[0018] The invention uses graphene as a carrier, connects iridium trichloride and tungsten hexachloride in a solvent thermal process to form an Ir-OW motif embedded in graphene oxide, and then regulates the size, distribution density and crystallinity of nanoclusters by chemical vapor deposition (CVD) to synthesize uniformly distributed sub-nanometer-sized iridium oxygen clusters; in the preparation process, since graphene oxide contains abundant defects, a large number of anchoring sites are provided for the uniform dispersion of iridium oxygen sub-nanometer clusters and tungsten single atoms; subsequently, in a high-temperature nitridation process, the introduction of nitrogen elements is beneficial to anchoring W atoms on graphene oxide; due to the difference in electronegativity, O atoms (EN=3.5) are more preferentially combined with adjacent metal atoms than N atoms (EN=3.0) to form stable covalent bonds, thereby realizing efficient oxygen bridge connection to improve the OER performance of the catalyst. The invention has a simple synthesis process, a short preparation cycle, and a cheap and readily available precursor, and has good application prospects. The invention uses a solvothermal method and a chemical vapor deposition (CVD) method, and then uses a high-valent W to induce the formation of a large number of iridium oxygen clusters on the surface to regulate the electronic structure and surface chemical properties of the material, and synthesizes an electrocatalyst W-IrO2 with W single atoms (W-N3O1) coupled with sub-nanometer-sized iridium oxygen clusters. x / NG.

[0019] The catalyst has excellent electrochemical performance for oxygen evolution, with high catalytic activity, stable performance, abundant and evenly distributed active sites, and can effectively reduce the overpotential of the oxygen evolution reaction and accelerate the reaction kinetics. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is the XRD pattern of Ir / NG prepared in Comparative Example 1;

[0021] Figure 2 The W-IrO prepared in Example 1 x XRD pattern of / NG;

[0022] Figure 3 This is the infrared spectrum of Ir / NG prepared in Comparative Example 1;

[0023] Figure 4 The W-IrO prepared in Example 1x / NG’s infrared spectrum;

[0024] Figure 5 This is the Raman spectrum of Ir / NG prepared in Comparative Example 1;

[0025] Figure 6 The W-IrO prepared in Example 1 x / Raman spectrum of NG;

[0026] Figure 7 The W-IrO prepared in Example 1 and Comparative Example 1 x HRTEM images of / NG and Ir / NG, where: a-20nm; b-10nm;

[0027] Figure 8 The W-IrO prepared in Example 1 and Comparative Example 1 x Schematic diagram of XPS total spectra and element contents of / NG and Ir / NG electrocatalysts;

[0028] Fig. 9 The W-IrO prepared in Example 1 and Comparative Example 1 x XPS fine structure peaks of Ir 4f and W 4f of / NG and Ir / NG electrocatalysts, where: a-Ir 4f; b-W 4f;

[0029] Fig.10 The W-IrO prepared in Example 1 and Comparative Example 1 x Schematic diagram of the acidic OER performance of Ir / NG and Ir / NG on a three-electrode system test device, where: a-polarization curve; b-corresponding Tafel plot;

[0030] Fig.11 The W-IrO prepared in Example 1 x CV curves and electrochemical double layer capacitance (C dl ), where: a-CV curve; b-corresponding electrochemical double layer capacitance (C dl );

[0031] Fig.12 The W-IrO prepared in Example 1 x Constant current test of / NG electrocatalyst in 0.5M H2SO4 solution (current density 10mAcm -2 ). DETAILED DESCRIPTION

[0032] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments.

[0033] The graphene oxide in the following embodiments is prepared by a modified Hummers method, and the specific process is as follows: in an ice-water bath at 0°C, 3g of graphite powder is dispersed in a mixed solution of concentrated H2SO4 / H3PO4 (360:40mL) with a volume ratio of 9:1, 18g of KMnO4 is slowly added and mechanically stirred continuously to oxidize the graphite powder and slowly release heat, then the water bath temperature is increased to 50°C and the reaction is maintained for 12h; after the solution is cooled to room temperature, it is poured into 400mL of crushed ice prepared in advance, stirred continuously until completely dissolved, and then an appropriate amount of H2O2 (30%) is slowly added to remove excess KMnO4 in the solution until the solution appears bright yellow; then centrifugation is performed, and the solution is repeatedly washed with a mass concentration of 30% HCl solution, deionized water and ether, and vacuum dried for more than 24h to obtain graphene oxide.

[0034] Example 1

[0035] A method for preparing a tungsten-induced sub-nanometer iridium-oxygen cluster electrocatalyst comprises the following steps:

[0036] S1: 30 mg of graphene oxide was ultrasonically dispersed in a solution of deionized water and anhydrous ethanol, wherein the volume of deionized water and anhydrous ethanol was 7.5 mL each, and ultrasonicated for 8 h to obtain a uniform suspension with a graphene oxide concentration of 2 mg / mL;

[0037] Add the metal content in the precursors iridium trichloride and tungsten hexachloride to the prepared graphene oxide suspension according to the atomic mass ratio loaded on graphene oxide (iridium atomic mass accounts for 5%, tungsten atomic mass accounts for 4%), adjust the pH of the solution to 11 with 0.5M NaOH, and ultrasonicate for 2h to obtain a uniformly dispersed precursor solution;

[0038] The precursor solution was transferred to a reaction kettle for a solvothermal reaction at a temperature of 180°C and a time of 12 hours. After the reaction was completed, a reaction product was obtained.

[0039] S2: placing the obtained reaction product in a freeze dryer for vacuum freeze drying for 12 hours to obtain a black columnar product; placing the black columnar product in the center of a tubular furnace and performing a high-temperature nitridation reaction by a chemical vapor deposition method. The process parameters of the chemical vapor deposition method are: furnace temperature of 800°C, reaction time of 2 hours, gas flow rate of Ar: 100sccm, NH3: 50sccm, and obtaining a tungsten-induced sub-nanometer iridium oxygen cluster electrocatalyst (W-IrO x / NG).

[0040] Example 2

[0041] A method for preparing a tungsten-induced sub-nanometer iridium-oxygen cluster electrocatalyst comprises the following steps:

[0042] S1: 30 mg of graphene oxide was ultrasonically dispersed in a solution of deionized water and anhydrous ethanol, wherein the volume of deionized water and anhydrous ethanol was 7.5 mL each, and ultrasonicated for 8 h to obtain a uniform suspension with a graphene oxide concentration of 2 mg / mL;

[0043] Add iridium trichloride trihydrate and tungsten hexachloride according to the atomic mass ratio of the loaded graphene oxide (iridium atomic mass accounts for 10%, tungsten atomic mass accounts for 4%) to the prepared graphene oxide suspension, adjust the pH of the solution to 11 with 0.5M NaOH, and ultrasonicate for 2h to obtain a uniformly dispersed precursor solution;

[0044] The precursor solution was transferred to a reaction kettle for a solvothermal reaction at a temperature of 180°C and a time of 12 hours. After the reaction was completed, a reaction product was obtained.

[0045] S2: placing the obtained reaction product in a freeze dryer for vacuum freeze drying for 12 hours to obtain a black columnar product; placing the black columnar product in the center of a tubular furnace and performing a high-temperature nitridation reaction by a chemical vapor deposition method. The process parameters of the chemical vapor deposition method are: heating reaction in a mixed atmosphere of Ar and NH3, the furnace temperature is 800°C, the reaction time is 2 hours, and the gas flow rate is Ar: 100sccm, NH3: 50sccm, to obtain a tungsten-induced sub-nanometer iridium oxygen cluster electrocatalyst (W-IrO x / NG-1).

[0046] Example 3

[0047] A method for preparing a tungsten-induced sub-nanometer iridium-oxygen cluster electrocatalyst comprises the following steps:

[0048] S1: 30 mg of graphene oxide was ultrasonically dispersed in a solution of deionized water and anhydrous ethanol, wherein the volume of deionized water and anhydrous ethanol was 7.5 mL each, and ultrasonicated for 8 h to obtain a uniform suspension with a graphene oxide concentration of 2 mg / mL;

[0049] Add iridium trichloride trihydrate and tungsten hexachloride according to the atomic mass ratio of the metals loaded on graphene oxide (iridium atomic mass accounts for 7.5%, tungsten atomic mass accounts for 4%) to the prepared graphene oxide suspension, adjust the pH of the solution to 11 with 0.5M NaOH, and ultrasonicate for 2 hours to obtain a uniformly dispersed precursor solution;

[0050] The precursor solution was transferred to a reaction kettle for a solvothermal reaction at a temperature of 180°C and a time of 12 hours. After the reaction was completed, a reaction product was obtained.

[0051] S2: placing the obtained reaction product in a freeze dryer for vacuum freeze drying for 12 hours to obtain a black columnar product; placing the black columnar product in the center of a tubular furnace and performing a high-temperature nitridation reaction by a chemical vapor deposition method. The process parameters of the chemical vapor deposition method are: heating reaction in a mixed atmosphere of Ar and NH3, the furnace temperature is 800°C, the reaction time is 2 hours, and the gas flow rate is Ar: 100sccm, NH3: 50sccm, to obtain a tungsten-induced sub-nanometer iridium oxygen cluster electrocatalyst (W-IrO x / NG-2).

[0052] Example 4

[0053] A method for preparing a tungsten-induced sub-nanometer iridium-oxygen cluster electrocatalyst comprises the following steps:

[0054] S1: 30 mg of graphene oxide was ultrasonically dispersed in a solution of deionized water and anhydrous ethanol, wherein the volume of deionized water and anhydrous ethanol was 7.5 mL each, and ultrasonicated for 8 h to obtain a uniform suspension with a graphene oxide concentration of 2 mg / mL;

[0055] Add iridium trichloride trihydrate and tungsten hexachloride according to the atomic mass ratio of the loaded graphene oxide (iridium atomic mass accounts for 2.5%, tungsten atomic mass accounts for 4%) to the prepared graphene oxide suspension, adjust the pH of the solution to 11 with 0.5M NaOH, and ultrasonicate for 2h to obtain a uniformly dispersed precursor solution;

[0056] The precursor solution was transferred to a reaction kettle for a solvothermal reaction at a temperature of 180°C and a time of 12 hours. After the reaction was completed, a reaction product was obtained.

[0057] S2: placing the obtained reaction product in a freeze dryer for vacuum freeze drying for 12 hours to obtain a black columnar product; placing the black columnar product in the center of a tubular furnace and performing a high-temperature nitridation reaction by a chemical vapor deposition method. The process parameters of the chemical vapor deposition method are: heating reaction in a mixed atmosphere of Ar and NH3, the furnace temperature is 800°C, the reaction time is 2 hours, and the gas flow rate is Ar: 100sccm, NH3: 50sccm, to obtain a tungsten-induced sub-nanometer iridium oxygen cluster electrocatalyst (W-IrO x / NG-3).

[0058] Example 5

[0059] A method for preparing a tungsten-induced sub-nanometer iridium-oxygen cluster electrocatalyst comprises the following steps:

[0060] S1: 30 mg of graphene oxide was ultrasonically dispersed in a solution of deionized water and anhydrous ethanol, wherein the volume of deionized water and anhydrous ethanol was 7.5 mL each, and ultrasonicated for 8 h to obtain a uniform suspension with a graphene oxide concentration of 2 mg / mL;

[0061] Add iridium trichloride trihydrate and tungsten hexachloride into the prepared graphene oxide suspension according to the atomic mass ratio of the metals loaded on graphene oxide (iridium atomic mass accounts for 5%, tungsten atomic mass accounts for 12%), adjust the pH of the solution to 11 with 0.5M NaOH, and ultrasonicate for 2h to obtain a uniformly dispersed precursor solution;

[0062] The precursor solution was transferred to a reaction kettle for a solvothermal reaction at a temperature of 180°C and a time of 12 hours. After the reaction was completed, a reaction product was obtained.

[0063] S2: placing the obtained reaction product in a freeze dryer for vacuum freeze drying for 12 hours to obtain a black columnar product; placing the black columnar product in the center of a tubular furnace and performing a high-temperature nitridation reaction by a chemical vapor deposition method. The process parameters of the chemical vapor deposition method are: heating reaction in a mixed atmosphere of Ar and NH3, the furnace temperature is 800°C, the reaction time is 2 hours, and the gas flow rate is Ar: 100sccm, NH3: 50sccm, to obtain a tungsten-induced sub-nanometer iridium oxygen cluster electrocatalyst (W-IrO x / NG-4).

[0064] Example 6

[0065] A method for preparing a tungsten-induced sub-nanometer iridium-oxygen cluster electrocatalyst comprises the following steps:

[0066] S1: 30 mg of graphene oxide was ultrasonically dispersed in a solution of deionized water and anhydrous ethanol, wherein the volume of deionized water and anhydrous ethanol was 7.5 mL each, and ultrasonicated for 8 h to obtain a uniform suspension with a graphene oxide concentration of 2 mg / mL;

[0067] Add iridium trichloride trihydrate and tungsten hexachloride according to the atomic mass ratio of the metals loaded on graphene oxide (iridium atomic mass accounts for 5%, tungsten atomic mass accounts for 8%) to the prepared graphene oxide suspension, adjust the pH of the solution to 11 with 0.5M NaOH, and ultrasonicate for 2h to obtain a uniformly dispersed precursor solution;

[0068] The precursor solution was transferred to a reaction kettle for a solvothermal reaction at a temperature of 180°C and a time of 12 hours. After the reaction was completed, a reaction product was obtained.

[0069] S2: placing the obtained reaction product in a freeze dryer for vacuum freeze drying for 12 hours to obtain a black columnar product; placing the black columnar product in the center of a tubular furnace and performing a high-temperature nitridation reaction by a chemical vapor deposition method. The process parameters of the chemical vapor deposition method are: heating reaction in a mixed atmosphere of Ar and NH3, the furnace temperature is 800°C, the reaction time is 2 hours, and the gas flow rate is Ar: 100sccm, NH3: 50sccm, to obtain a tungsten-induced sub-nanometer iridium oxygen cluster electrocatalyst (W-IrO x / NG-5).

[0070] Example 7

[0071] A method for preparing a tungsten-induced sub-nanometer iridium-oxygen cluster electrocatalyst comprises the following steps:

[0072] S1: 30 mg of graphene oxide was ultrasonically dispersed in a solution of deionized water and anhydrous ethanol, wherein the volume of deionized water and anhydrous ethanol was 7.5 mL each, and ultrasonicated for 8 h to obtain a uniform suspension with a graphene oxide concentration of 2 mg / mL;

[0073] Add iridium trichloride trihydrate and tungsten hexachloride according to the atomic mass ratio of the loaded graphene oxide (iridium atomic mass accounts for 5%, tungsten atomic mass accounts for 2%) to the prepared graphene oxide suspension, adjust the pH of the solution to 11 with 0.5M NaOH, and ultrasonicate for 2h to obtain a uniformly dispersed precursor solution;

[0074] The precursor solution was transferred to a reaction kettle for a solvothermal reaction at a temperature of 180°C and a time of 12 hours. After the reaction was completed, a reaction product was obtained.

[0075] S2: placing the obtained reaction product in a freeze dryer for vacuum freeze drying for 12 hours to obtain a black columnar product; placing the black columnar product in the center of a tubular furnace and performing a high-temperature nitridation reaction by a chemical vapor deposition method. The process parameters of the chemical vapor deposition method are: heating reaction in a mixed atmosphere of Ar and NH3, the furnace temperature is 800°C, the reaction time is 2 hours, and the gas flow rate is Ar: 100sccm, NH3: 50sccm, to obtain a tungsten-induced sub-nanometer iridium oxygen cluster electrocatalyst (W-IrO x / NG-6).

[0076] Comparative Example 1

[0077] A method for preparing an iridium nanocrystal oxygen evolution electrocatalyst comprises the following steps:

[0078] S1: 30 mg of graphene oxide was ultrasonically dispersed in a solution of deionized water and anhydrous ethanol, wherein the volume of deionized water and anhydrous ethanol was 7.5 mL each, and ultrasonicated for 8 h to obtain a uniform suspension with a graphene oxide concentration of 2 mg / mL;

[0079] Add the metal content of iridium trichloride trihydrate to the prepared graphene oxide suspension according to the atomic mass ratio of the metal loaded on the graphene oxide (the atomic mass of iridium accounts for 5%), and ultrasonicate for 2 hours to obtain a uniformly dispersed precursor solution;

[0080] The precursor solution was transferred to a reaction kettle for a solvothermal reaction at a temperature of 180°C and a time of 12 hours. After the reaction was completed, a reaction product was obtained.

[0081] S2: placing the obtained reaction product in a freeze dryer for vacuum freeze drying treatment, the freeze drying time is 12 hours, and a black columnar product is obtained; placing the black columnar product in the center of a tubular furnace, and performing a high-temperature nitridation reaction by a chemical vapor deposition method. The process parameters of the chemical vapor deposition method are: heating reaction in a mixed atmosphere of Ar and NH3, the furnace temperature is 800°C, the reaction time is 2 hours, and the gas flow rate is Ar: 100sccm, NH3: 50sccm, to obtain an iridium nanocrystal oxygen evolution electrocatalyst (Ir / NG).

[0082] Comparative Example 2

[0083] A method for preparing a tungsten single-atom oxygen evolution electrocatalyst comprises the following steps:

[0084] S1: 30 mg of graphene oxide was ultrasonically dispersed in a solution of deionized water and anhydrous ethanol, wherein the volume of deionized water and anhydrous ethanol was 7.5 mL each, and ultrasonicated for 8 h to obtain a uniform suspension with a graphene oxide concentration of 2 mg / mL;

[0085] Add the metal content in tungsten hexachloride to the prepared graphene oxide suspension according to the atomic mass ratio of tungsten loaded on graphene oxide (the atomic mass of tungsten accounts for 4%), and ultrasonicate for 2 hours to obtain a uniformly dispersed precursor solution;

[0086] The precursor solution was transferred to a reaction kettle for a solvothermal reaction at a temperature of 180°C and a time of 12 hours. After the reaction was completed, a reaction product was obtained.

[0087] S2: The obtained reaction product is placed in a freeze dryer for vacuum freeze drying treatment. The freeze drying time is 12 hours to obtain a black columnar product; the black columnar product is placed in the center of a tubular furnace and subjected to a high-temperature nitridation reaction by a chemical vapor deposition method. The process parameters of the chemical vapor deposition method are: heating reaction in a mixed atmosphere of Ar and NH3, the furnace temperature is 800°C, the reaction time is 2 hours, and the gas flow rates are Ar: 100sccm, NH3: 50sccm, to obtain a tungsten single atom oxygen evolution electrocatalyst (W / NG).

[0088] The performance of the catalysts prepared in Example 1 and Comparative Example 1 was evaluated and characterized as follows:

[0089] The iron-nickel electrocatalyst rich in oxygen defects was used as a catalyst in the electrocatalytic oxygen evolution reaction to generate oxygen: the electrochemical test was carried out using a CH Instruments760E electrochemical workstation in a three-electrode battery test system; 2 mg of the catalyst was ultrasonically dispersed in a mixture of 400 μL of ethanol, 100 μL of water and 40 μL of 5% Nafion solution for 20 minutes to prepare a catalyst dispersion. 5 μL of the catalyst dispersion was drop-coated on a glassy carbon electrode (3 mm in diameter) twice and dried naturally for at least 24 hours before testing. In an O2-saturated 0.5 M H2SO4 electrolyte solution, a platinum wire was used as the counter electrode and a saturated calomel electrode (SCE) was used as the reference electrode; all potentials were referenced to the reversible hydrogen electrode RHE:E RHE =E SCE +(0.242+0.059pH)V, and all data were without iR compensation. Before the experiment, the samples were scanned at a rate of 100 mV s in a 0.5 M H2SO4 aqueous solution saturated with nitrogen or oxygen. -1 Cyclic voltammetry (CV) was used to activate the electrode for 30 min. Linear sweep voltammetry (LSV) was used in an oxygen-saturated electrolyte at 1.05–1.7 V at 5 mV s -1 The polarization curves were obtained at a scan rate of 10. -2 to 10 6 Hz range.

[0090] The sub-nanometer-sized iridium-oxygen cluster electrocatalyst can maintain the performance of efficient acidic water decomposition to generate oxygen, with an overpotential of 220 mV and a low Tafel slope, and has high stability, demonstrating good OER performance.

[0091] like Figure 1Shown is the XRD pattern of the Ir / NG electrocatalyst prepared in Comparative Example 1, in which three obvious diffraction peaks at 40.7°, 47.3° and 69.1° belong to the (111), (200) and (220) crystal planes of Ir, respectively, indicating that the formed Ir crystals are loaded on the graphene substrate.

[0092] like Figure 2 The sub-nano cluster IrO prepared in Example 1 is shown. x W-IrO coupled with W single atom (W-N3O1) x The XRD pattern of W-IrO / NG electrocatalyst shows that there are three obvious diffraction peaks at 40.7°, 47.3° and 69.1°, which belong to the (111), (200) and (220) crystal planes of Ir, respectively. x The (111) crystal plane of the / NG electrocatalyst shifts to a high angle, indicating that the presence of W makes the W-IrO x / NG's lattice structure is distorted.

[0093] like Figure 3 The infrared spectrum of the Ir / NG electrocatalyst prepared in Comparative Example 1 is shown. It can be seen from the figure that the Ir / NG electrocatalyst has abundant oxygen functional groups, 3300-2800 cm -1 CH stretching vibration absorption region; 2270~2100cm -1 It is the characteristic peak of the stretching vibration absorption of C≡C bond; 1680~1640cm -1 It is the characteristic peak of the stretching vibration absorption of unsaturated carbon-carbon bond (C=C).

[0094] like Figure 4 The sub-nano cluster IrO prepared in Example 1 is shown. x W-IrO coupled with W single atom (W-N3O1) x Infrared spectrum of W-IrO / NG electrocatalyst. x / NG electrocatalyst has abundant oxygen functional groups, 3469 cm -1 The stretching vibration absorption of OH bond is at 1346cm -1 It is the characteristic peak of CN stretching vibration absorption; 800~1200cm -1 It is the characteristic peak of WO- stretching vibration absorption.

[0095] like Figure 5 The Raman spectrum of the Ir / NG electrocatalyst prepared in Comparative Example 1 is shown. The D peak (1348 cm -1 ) is caused by disordered carbon atoms, and the G peak is caused by sp 2The intensity ratio of D peak to G peak (I D / I G ) is 0.98.

[0096] like Figure 6 The W-IrO prepared in Example 1 is shown. x Raman spectrum of / NG electrocatalyst, D peak (1348cm -1 ) is caused by disordered carbon atoms, and the G peak is caused by sp 2 The intensity ratio of D peak to G peak (I D / I G ) is 1.02.

[0097] like Figure 7 a and Figure 7 b are W-IrO prepared in Example 1 and Comparative Example 1, respectively. x The high-magnification TEM images of W-IrO / NG and Ir / NG both show a layered structure with abundant wrinkles and ripples. This morphology is conducive to exposing more active sites and promoting electrochemical reactions on the surface. x There are a large number of uniform sub-nanometer clusters distributed on the surface of W-IrO / NG, and the average size is smaller than that of the undoped tungsten Ir / NG electrocatalyst, and there is no agglomeration phenomenon. x In / NG, tungsten exists in the form of single atoms, and iridium exists mainly in the form of iridium oxide clusters, indicating that tungsten doping induces the formation of iridium oxide subnanoclusters under high temperature conditions.

[0098] like Figure 8 a and Figure 8 b shows the W-IrO prepared in Example 1 and Comparative Example 1. x The XPS total spectrum and element content diagram of the electrocatalysts of W-IrO / NG and Ir / NG. x / NG and Ir / NG both contain characteristic peaks of C, N, O, and Ir. x In the / NG catalyst, C:89.5, N:2.47, O:6.49, Ir:1.07, W:0.47; in the Ir / NG catalyst, C:78.27, N:3.89, O:16.54, Ir:1.32.

[0099] like Fig. 9 a and Fig. 9 b are W-IrO prepared in Example 1 and Comparative Example 1, respectively.x XPS fine structure peaks of Ir 4f and W 4f of Ir / NG and Ir / NG electrocatalysts are shown in Fig. 9 In the Ir 4f fine spectrum, Ir 0 (60.8 and 63.8 eV), Ir 4+ (61.6 and 64.7 eV), the doping of tungsten did not affect the oxidation state of iridium; Fig. 9 bW-IrO x The peak of WN (32.0 eV) species in the W4f fine spectrum of W-IrO / NG is negatively shifted by 0.5 eV, proving that electrons are transferred between WN. x The WN content in / NG increased more significantly than that in W / NG.

[0100] like Fig.10 The figure shows the acidic OER performance of the electrocatalysts prepared in Example 1 and Comparative Example 1 in a three-electrode battery test system of a CH Instruments 760E electrochemical workstation. Fig.10 a and Fig.10 b are the polarization curves and the corresponding Tafel slopes in 0.5MH2SO4 electrolyte, where W-IrO x / NG overpotential (220mV) and Tafel slope (84.9mV dec -1 ) are superior to Ir / NG, revealing its more excellent OER performance.

[0101] like Fig.11 The W-IrO prepared in Example 1 is shown in FIG. x The performance of the / NG electrocatalyst in the acidic OER test system of the CH Instruments760E electrochemical workstation is shown. Fig.11 a and Fig.11 b CV curves and electrochemical double layer capacitance (C dl ), the W-IrO x C / NG catalyst dl (12.2mF / cm 2 ), which is mainly due to the increase in specific surface area caused by the sub-nanometer-sized iridium-oxygen clusters induced by tungsten, resulting in enhanced catalytic activity, indicating that W-IrO x / NG electrocatalysts exhibit excellent OER activity.

[0102] like Fig.12 The W-IrO prepared in Example 1 is shown in FIG. xConstant current test of / NG electrocatalyst in 0.5M H2SO4 solution (current density 10mAcm -2 ). At 10mAcm -2 At high current density, W-IrO x The / NG catalyst did not show obvious deactivation in the 240-hour long-term stability test, which proves that the catalyst has good stability in the oxygen evolution process of acidic water electrolysis.

Claims

1. A method for preparing a tungsten-induced sub-nanometer iridium-oxygen cluster electrocatalyst, characterized in that: The following steps are involved: S1. adding an iridium source, a tungsten source, and graphene oxide to a mixed solvent consisting of water and anhydrous ethanol to obtain a precursor solution; adjusting the pH value of the precursor solution to a strongly alkaline state, and then performing a solvothermal reaction to obtain a reaction product; S2. Drying the reaction product, and then performing high-temperature nitridation using a chemical vapor deposition method to obtain a sub-nanometer iridium oxide cluster electrocatalyst.

2. The preparation method according to claim 1, characterized in that The percentage of iridium in the iridium source to the mass of graphene oxide is 2.5-10%; the percentage of tungsten in the tungsten source to the mass of graphene oxide is 2-12%.

3. The preparation method according to claim 1, characterized in that In step S1, graphene oxide is dispersed in a mixed solution of water and anhydrous ethanol, and ultrasonically treated for 4 to 8 hours to obtain a graphene oxide suspension. Then, an iridium source and a tungsten source are added to the graphene oxide suspension, and ultrasonicated for 1 to 4 hours to obtain a precursor solution.

4. The preparation method according to claim 1 or 3, characterized in that The mass volume ratio of the graphene oxide, water and anhydrous ethanol is: 4 mg: 1 mL: 1 mL.

5. The preparation method according to any one of claims 1 to 3, characterized in that The iridium source is iridium trichloride; the tungsten source is tungsten hexachloride.

6. The preparation method according to claim 1, characterized in that In step S1, the temperature of the solvent thermal reaction is 160-200° C., and the reaction time is 10-18 hours.

7. The preparation method according to claim 1, characterized in that In step S2, the drying process is freeze-drying process, and the freeze-drying process time is 2 to 15 hours.

8. The preparation method according to claim 1, characterized in that In step S2, the high-temperature nitridation using the chemical vapor deposition method includes the following steps: nitridation is performed in a mixed atmosphere of argon and ammonia, the reaction temperature is 600-1000°C, the reaction time is 1-3h, the argon flow rate is 100±50sccm, and the ammonia flow rate is 50±10sccm.

9. An electrocatalyst prepared by the preparation method according to any one of claims 1 to 8.

10. Use of the electrocatalyst according to claim 9 as an electrocatalyst for generating oxygen in an acidic oxygen evolution reaction.

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