Preparation method of tungsten-induced sub-nanometer iridium oxygen cluster electrocatalyst, electrocatalyst and application thereof
By synthesizing tungsten-induced sub-nanometer iridium-oxygen cluster electrocatalysts on graphene oxide, the problems of difficult deprotonation of IrOx nanoclusters in intermediates and poor high-potential stability were solved, and high-efficiency OER performance was achieved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- XI AN JIAOTONG UNIV
- Filing Date
- 2025-01-06
- Publication Date
- 2026-07-03
AI Technical Summary
Existing IrOx nanoclusters exhibit difficulties in direct surface deprotonation of intermediates and have poor stability in high-potential regions, affecting OER catalytic performance. Furthermore, the surface energy increases as the particle size decreases, leading to Ir atom aggregation and crystal growth into larger crystals, which impairs electrochemical activity.
Tungsten-induced sub-nanometer iridium-oxygen cluster electrocatalysts were synthesized on graphene oxide using a solvothermal method and chemical vapor deposition. The Ir-OW motifs were embedded into graphene oxide, and high-temperature nitridation was used to form bridging oxygen-linked W single-atom coupled sub-nanometer iridium-oxygen clusters. The electronic structure and surface chemical properties were controlled to suppress the excessive oxidation of iridium.
It improves OER activity, has high catalytic activity and stable performance, has abundant and uniformly distributed active sites, reduces the overpotential of oxygen evolution reaction, and accelerates the reaction kinetics.
Smart Images
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Abstract
Description
Technical Field
[0001] This invention belongs to the field of electrochemical catalysis technology, and specifically relates to a method for preparing a tungsten-induced sub-nanometer iridium-oxygen cluster electrocatalyst, the electrocatalyst itself, and its applications. Background Technology
[0002] The oxygen evolution reaction (OER) is a key component of various renewable electrochemical technologies in the field of energy conversion. Anodic OER consists of a complex proton-coupled four-electron transfer step, typically requiring high energies to overcome the reaction barrier, which severely limits the overall efficiency of water electrolysis. In recent years, iridium-based materials have been widely considered as state-of-the-art OER electrocatalysts due to their excellent intrinsic activity. Among them, IrO... x Nanoclusters possess abundant active sites, electrophilic oxygen properties, and excellent corrosion resistance under acidic conditions, making them stand out among iridium-based electrocatalysts. Unfortunately, IrO... x Nanoclusters exhibit considerable difficulty in direct surface deprotonation of intermediates and show poor stability in the high-potential region (>1.6V), which severely affects OER catalytic performance. Furthermore, as particle size decreases, surface energy increases rapidly, leading to strong aggregation of Ir atoms and further crystal growth into larger crystals, which significantly impairs electrochemical OER activity. Summary of the Invention
[0003] The purpose of this invention is to provide a method for preparing tungsten-induced sub-nanometer iridium-oxygen cluster electrocatalysts, the electrocatalysts themselves, and their applications, in order to solve the technical problems of existing preparation methods in how to achieve rapid deprotonation of intermediates and over-oxidation of catalytic sites in high-voltage regions.
[0004] To achieve the above objectives, the technical solution adopted by the present invention is as follows:
[0005] A method for preparing a tungsten-induced sub-nanometer iridium-oxygen cluster electrocatalyst includes the following steps:
[0006] S1. Iridium source, tungsten source, and graphene oxide are added to a mixed solvent consisting of deionized water and anhydrous ethanol to obtain a precursor solution. The pH of the precursor solution is adjusted to a strongly alkaline state using sodium hydroxide, with a pH of 9-11. Then, a solvothermal reaction is carried out to obtain the reaction product.
[0007] S2. The reaction product is dried and then subjected to high-temperature nitridation using chemical vapor deposition to obtain a sub-nanometer iridium-oxygen cluster electrocatalyst.
[0008] Preferably, the iridium in the iridium source accounts for 2.5% to 10% of the mass of graphene oxide; and the tungsten in the tungsten source accounts for 2% to 12% of the mass of graphene oxide.
[0009] Preferably, in step S1, graphene oxide is dispersed in a mixed solution of deionized water and anhydrous ethanol and ultrasonically treated for 4-8 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. Then, an iridium source and a tungsten source are added to the graphene oxide suspension and ultrasonically treated for 1-4 hours to obtain a precursor solution.
[0010] Preferably, the mass-to-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; the tungsten source is tungsten hexachloride.
[0012] Preferably, in step S1, the temperature of the solvothermal reaction is 160–200°C, and the reaction time is 10–18 h.
[0013] Preferably, in step S2, the drying process is freeze-drying, and the freeze-drying time is 2 to 15 hours.
[0014] Preferably, in step S2, the high-temperature nitriding using chemical vapor deposition includes the following steps: nitriding is carried out in a mixed atmosphere of argon and ammonia, with a reaction temperature of 600–1000°C, a reaction time of 1–3 h, an argon flow rate of 100 ± 50 sccm, and an ammonia flow rate of 50 ± 10 sccm.
[0015] In another aspect, the present invention provides an electrocatalyst prepared by the preparation method described above.
[0016] In another aspect, the present invention provides the application of the above-described electrocatalyst as an electrocatalyst for the generation of oxygen in an acidic oxygen evolution reaction.
[0017] This invention utilizes iridium trichloride (IrCl3) and tungsten hexachloride (WCl6) as iridium and tungsten sources, respectively, and ammonia (NH3) as a nitrogen source, to synthesize sub-nanometer-sized iridium-oxygen cluster electrocatalysts at high temperatures using a solvothermal method and chemical vapor deposition (CVD). In a strongly alkaline solution, IrCl3 undergoes hydrolysis and condensation to form [Ir(OH)6], which has an Ir-O oligomer structure. 3- The anion, WCl6, reacts with ethanol via a non-hydrolytic conversion to generate tungsten oxide (WCl6) with oxygen vacancies. 18 O 49 It can anchor negatively charged [Ir(OH)6] 3- [Ir(OH)6] 3-Anions are inserted into the oxygen vacancies of tungsten oxide formed by the conversion of WCl6 and loaded onto graphene oxide. Due to the gradual increase in 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 nitriding conditions, a bridged oxygen-linked W single-atom coupled sub-nanometer iridium-oxygen cluster (IrOx) electrocatalyst is formed. The introduction of high-valence W single atoms (W-N3O1) as electron-rich groups effectively regulates the local electron distribution of IrOx, significantly improving OER activity and inhibiting the over-oxidation of iridium.
[0018] This invention uses graphene as a carrier, where iridium trichloride and tungsten hexachloride are linked during a solvothermal process to form Ir-OW motifs that are embedded into graphene oxide. Subsequently, the size, distribution density, and crystallinity of the nanoclusters are controlled by chemical vapor deposition (CVD) to synthesize uniformly distributed sub-nanometer-sized iridium-oxygen clusters. During the preparation process, the abundance of defects in graphene oxide provides numerous anchoring sites for the uniform dispersion of iridium-oxygen sub-nanometer clusters and tungsten single atoms. Subsequently, the introduction of nitrogen during high-temperature nitriding is beneficial for anchoring W atoms on graphene oxide. Due to the difference in electronegativity, O atoms (EN = 3.5) preferentially combine with neighboring metal atoms to form stable covalent bonds than N atoms (EN = 3.0), achieving efficient oxygen bridging to improve the OER performance of the catalyst. The synthesis process of this invention is simple, the preparation cycle is short, and the precursors are inexpensive and readily available, showing good application prospects. Through solvothermal and chemical vapor deposition (CVD) methods, and by controlling the electronic structure and surface chemical properties of the material based on the formation of a large number of iridium-oxygen clusters on the surface induced by high-valence W, an electrocatalyst W-IrO3 coupled with sub-nanometer-sized iridium-oxygen clusters was synthesized. x / NG.
[0019] This catalyst exhibits excellent oxygen evolution electrochemical performance, with high catalytic activity, stable performance, abundant and uniformly distributed active sites, which can effectively reduce the overpotential of the oxygen evolution reaction and accelerate the reaction kinetics. Attached Figure Description
[0020] Figure 1 The XRD pattern of Ir / NG prepared in Comparative Example 1;
[0021] Figure 2 W-IrO prepared in Example 1 x XRD pattern of / NG;
[0022] Figure 3 The infrared spectrum of Ir / NG prepared in Comparative Example 1 is shown.
[0023] Figure 4 W-IrO prepared in Example 1x / NG infrared spectrum;
[0024] Figure 5 The Raman spectrum of Ir / NG prepared in Comparative Example 1 is shown below.
[0025] Figure 6 W-IrO prepared in Example 1 x Raman spectrum of / NG;
[0026] Figure 7 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 W-IrO prepared in Example 1 and Comparative Example 1 x Schematic diagram of XPS total spectra and elemental contents of / NG and Ir / NG electrocatalysts;
[0028] Figure 9 W-IrO prepared in Example 1 and Comparative Example 1 x XPS fine structure peaks of Ir 4f and W 4f in / NG and Ir / NG electrocatalysts, where: a-Ir 4f; b-W 4f;
[0029] Figure 10 W-IrO prepared in Example 1 and Comparative Example 1 x Schematic diagram of the acidic OER performance of / NG and Ir / NG on a three-electrode system test device, where: a-polarization curve; b-corresponding Tafel plot;
[0030] Figure 11 W-IrO prepared in Example 1 x CV curves and electrochemical double-layer capacitance (CNG) of the / NG electrocatalyst at different scan rates in the non-Radida potential region dl ), where: a-CV curve; b-corresponding electrochemical double-layer capacitance (C dl );
[0031] Figure 12 W-IrO prepared in Example 1 x Current galvanostatic testing of / NG electrocatalyst in 0.5M H2SO4 solution (current density 10 mA / cm²) -2 ). Detailed Implementation
[0032] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.
[0033] The graphene oxide in the following examples was prepared by a modified Hummers method, the specific process of which is as follows: 3g of graphite powder was dispersed in a mixed solution of concentrated H2SO4 / H3PO4 (360:40mL) with a volume ratio of 9:1 in an ice-water bath at 0°C. 18g of KMnO4 was slowly added while continuously stirring mechanically to oxidize the graphite powder and slowly release heat. The water bath temperature was then increased to 50°C and the reaction was maintained for 12 hours. After the solution cooled to room temperature, it was poured into 400mL of pre-prepared crushed ice and stirred continuously until completely dissolved. Then, an appropriate amount of H2O2 (30%) was slowly added to remove excess KMnO4 from the solution until the solution turned bright yellow. Subsequently, the solution was separated by centrifugation and washed repeatedly with 30% HCl solution, deionized water, and diethyl ether. The solution was then vacuum dried for more than 24 hours to obtain graphene oxide.
[0034] Example 1
[0035] A method for preparing a tungsten-induced sub-nanometer iridium-oxygen cluster electrocatalyst includes 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. The mixture was ultrasonicated for 8 h to obtain a uniform suspension with a graphene oxide concentration of 2 mg / mL.
[0037] The metal content of the precursors iridium trichloride and tungsten hexachloride was added to the prepared graphene oxide suspension according to the atomic mass ratio of iridium atoms loaded on graphene oxide (iridium atomic mass ratio of 5% and tungsten atomic mass ratio of 4%). The pH of the solution was adjusted to 11 using 0.5M NaOH and sonicated for 2 hours to obtain a uniformly dispersed precursor solution.
[0038] The precursor solution was transferred to a reaction vessel for a solvothermal reaction at a temperature of 180°C for 12 hours. After the reaction was completed, the reaction product was obtained.
[0039] S2: The obtained reaction product was placed in a freeze dryer and subjected to vacuum freeze-drying for 12 hours to obtain a black columnar product. The black columnar product was then placed in the center of a tube furnace and subjected to a high-temperature nitriding reaction using chemical vapor deposition (CVD). The CVD process parameters were: furnace temperature 800℃, reaction time 2 hours, and gas flow rates of Ar: 100 sccm and NH3: 50 sccm, to obtain 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 includes 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. The mixture was ultrasonicated for 8 h to obtain a uniform suspension with a graphene oxide concentration of 2 mg / mL.
[0043] The metal content of iridium trichloride trihydrate and tungsten hexachloride was added to the prepared graphene oxide suspension according to the atomic mass ratio of iridium atoms loaded on graphene oxide (iridium atomic mass ratio of 10% and tungsten atomic mass ratio of 4%). The pH of the solution was adjusted to 11 using 0.5M NaOH and sonicated for 2 hours to obtain a uniformly dispersed precursor solution.
[0044] The precursor solution was transferred to a reaction vessel for a solvothermal reaction at a temperature of 180°C for 12 hours. After the reaction was completed, the reaction product was obtained.
[0045] S2: The obtained reaction product was placed in a freeze dryer and subjected to vacuum freeze-drying for 12 hours to obtain a black columnar product. The black columnar product was then placed in the center of a tube furnace and subjected to a high-temperature nitriding reaction using chemical vapor deposition (CVD). The CVD process parameters were as follows: heating reaction under a mixed atmosphere of Ar and NH3, furnace temperature of 800℃, reaction time of 2 hours, and gas flow rates of Ar: 100 sccm and NH3: 50 sccm, 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 includes 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. The mixture was ultrasonicated for 8 h to obtain a uniform suspension with a graphene oxide concentration of 2 mg / mL.
[0049] The metal content of iridium trichloride trihydrate and tungsten hexachloride was added to the prepared graphene oxide suspension according to the atomic mass ratio of iridium atomic mass to tungsten atomic mass (7.5% and 4%) loaded on graphene oxide. The pH of the solution was adjusted to 11 using 0.5M NaOH and sonicated for 2 hours to obtain a uniformly dispersed precursor solution.
[0050] The precursor solution was transferred to a reaction vessel for a solvothermal reaction at a temperature of 180°C for 12 hours. After the reaction was completed, the reaction product was obtained.
[0051] S2: The obtained reaction product was placed in a freeze dryer and subjected to vacuum freeze-drying for 12 hours to obtain a black columnar product. The black columnar product was then placed in the center of a tube furnace and subjected to a high-temperature nitriding reaction using chemical vapor deposition (CVD). The CVD process parameters were as follows: heating reaction under a mixed atmosphere of Ar and NH3, furnace temperature of 800℃, reaction time of 2 hours, and gas flow rates of Ar: 100 sccm and NH3: 50 sccm, 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 includes 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. The mixture was ultrasonicated for 8 h to obtain a uniform suspension with a graphene oxide concentration of 2 mg / mL.
[0055] The metal content of iridium trichloride trihydrate and tungsten hexachloride was added to the prepared graphene oxide suspension according to the atomic mass ratio of iridium atomic mass to tungsten atomic mass to graphene oxide (iridium atomic mass ratio of 2.5% and tungsten atomic mass ratio of 4%). The pH of the solution was adjusted to 11 using 0.5M NaOH and sonicated for 2 hours to obtain a uniformly dispersed precursor solution.
[0056] The precursor solution was transferred to a reaction vessel for a solvothermal reaction at a temperature of 180°C for 12 hours. After the reaction was completed, the reaction product was obtained.
[0057] S2: The obtained reaction product was placed in a freeze dryer and subjected to vacuum freeze-drying for 12 hours to obtain a black columnar product. The black columnar product was then placed in the center of a tube furnace and subjected to a high-temperature nitriding reaction using chemical vapor deposition (CVD). The CVD process parameters were as follows: heating reaction under a mixed atmosphere of Ar and NH3, furnace temperature of 800℃, reaction time of 2 hours, and gas flow rates of Ar: 100 sccm and NH3: 50 sccm, 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 includes 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. The mixture was ultrasonicated for 8 h to obtain a uniform suspension with a graphene oxide concentration of 2 mg / mL.
[0061] The metal content of iridium trichloride trihydrate and tungsten hexachloride was added to the prepared graphene oxide suspension according to the atomic mass ratio of iridium atomic mass to tungsten atomic mass to graphene oxide (iridium atomic mass ratio of 5% and tungsten atomic mass ratio of 12%). The pH of the solution was adjusted to 11 using 0.5M NaOH and sonicated for 2 hours to obtain a uniformly dispersed precursor solution.
[0062] The precursor solution was transferred to a reaction vessel for a solvothermal reaction at a temperature of 180°C for 12 hours. After the reaction was completed, the reaction product was obtained.
[0063] S2: The obtained reaction product was placed in a freeze dryer and subjected to vacuum freeze-drying for 12 hours to obtain a black columnar product. The black columnar product was then placed in the center of a tube furnace and subjected to a high-temperature nitriding reaction using chemical vapor deposition (CVD). The CVD process parameters were as follows: heating reaction under a mixed atmosphere of Ar and NH3, furnace temperature of 800℃, reaction time of 2 hours, and gas flow rates of Ar: 100 sccm and NH3: 50 sccm, 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 includes 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. The mixture was ultrasonicated for 8 h to obtain a uniform suspension with a graphene oxide concentration of 2 mg / mL.
[0067] The metal content of iridium trichloride trihydrate and tungsten hexachloride was added to the prepared graphene oxide suspension according to the atomic mass ratio of iridium atomic mass to tungsten atomic mass to graphene oxide (iridium atomic mass ratio of 5% and tungsten atomic mass ratio of 8%). The pH of the solution was adjusted to 11 using 0.5M NaOH and sonicated for 2 hours to obtain a uniformly dispersed precursor solution.
[0068] The precursor solution was transferred to a reaction vessel for a solvothermal reaction at a temperature of 180°C for 12 hours. After the reaction was completed, the reaction product was obtained.
[0069] S2: The obtained reaction product was placed in a freeze dryer and subjected to vacuum freeze-drying for 12 hours to obtain a black columnar product. The black columnar product was then placed in the center of a tube furnace and subjected to a high-temperature nitriding reaction using chemical vapor deposition (CVD). The CVD process parameters were as follows: heating reaction under a mixed atmosphere of Ar and NH3, furnace temperature of 800℃, reaction time of 2 hours, and gas flow rates of Ar: 100 sccm and NH3: 50 sccm, 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 includes 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. The mixture was ultrasonicated for 8 h to obtain a uniform suspension with a graphene oxide concentration of 2 mg / mL.
[0073] The metal content of iridium trichloride trihydrate and tungsten hexachloride was added to the prepared graphene oxide suspension according to the atomic mass ratio of iridium atoms loaded on graphene oxide (iridium atomic mass ratio of 5% and tungsten atomic mass ratio of 2%). The pH of the solution was adjusted to 11 using 0.5M NaOH and sonicated for 2 hours to obtain a uniformly dispersed precursor solution.
[0074] The precursor solution was transferred to a reaction vessel for a solvothermal reaction at a temperature of 180°C for 12 hours. After the reaction was completed, the reaction product was obtained.
[0075] S2: The obtained reaction product was placed in a freeze dryer and subjected to vacuum freeze-drying for 12 hours to obtain a black columnar product. The black columnar product was then placed in the center of a tube furnace and subjected to a high-temperature nitriding reaction using chemical vapor deposition (CVD). The CVD process parameters were as follows: heating reaction under a mixed atmosphere of Ar and NH3, furnace temperature of 800℃, reaction time of 2 hours, and gas flow rates of Ar: 100 sccm and NH3: 50 sccm, 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 oxygen evolution electrocatalyst based on iridium nanocrystals includes 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. The mixture was ultrasonicated for 8 h to obtain a uniform suspension with a graphene oxide concentration of 2 mg / mL.
[0079] The metal content of iridium trichloride trihydrate was added to the prepared graphene oxide suspension according to the atomic mass ratio of iridium atoms loaded on graphene oxide (iridium atomic mass ratio of 5%), and ultrasonicated for 2 hours to obtain a uniformly dispersed precursor solution.
[0080] The precursor solution was transferred to a reaction vessel for a solvothermal reaction at a temperature of 180°C for 12 hours. After the reaction was completed, the reaction product was obtained.
[0081] S2: The obtained reaction product was placed in a freeze dryer and subjected to vacuum freeze drying for 12 hours to obtain a black columnar product. The black columnar product was placed in the center of a tube furnace and subjected to a high-temperature nitriding reaction using chemical vapor deposition. The process parameters of the chemical vapor deposition method were as follows: the reaction was carried out under a mixed atmosphere of Ar and NH3, the furnace temperature was 800℃, the reaction time was 2 hours, and the gas flow rate was Ar: 100 sccm and NH3: 50 sccm 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 includes 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. The mixture was ultrasonicated for 8 h to obtain a uniform suspension with a graphene oxide concentration of 2 mg / mL.
[0085] The metal content of tungsten hexachloride was added to the prepared graphene oxide suspension according to the atomic mass ratio of tungsten atoms loaded on graphene oxide (4% of the atomic mass of tungsten). The suspension was sonicated for 2 hours to obtain a uniformly dispersed precursor solution.
[0086] The precursor solution was transferred to a reaction vessel for a solvothermal reaction at a temperature of 180°C for 12 hours. After the reaction was completed, the reaction product was obtained.
[0087] S2: The obtained reaction product was placed in a freeze dryer and subjected to vacuum freeze drying for 12 hours to obtain a black columnar product. The black columnar product was placed in the center of a tube furnace and subjected to high-temperature nitriding reaction by chemical vapor deposition. The process parameters of the chemical vapor deposition method were as follows: heating reaction was carried out in a mixed atmosphere of Ar and NH3, furnace temperature was 800℃, reaction time was 2 hours, and gas flow rate was Ar: 100 sccm, NH3: 50 sccm to obtain a tungsten single-atom oxygen evolution electrocatalyst (W / NG).
[0088] The catalysts prepared in Example 1 and Comparative Example 1 were evaluated and characterized in the following ways:
[0089] An oxygen-defect-rich iron-nickel electrocatalyst was used as a catalyst in the electrocatalytic oxygen evolution reaction (OER) to produce oxygen. Electrochemical tests were conducted using a CH Instruments 760E electrochemical workstation in a three-electrode cell system. 2 mg of catalyst was ultrasonically dispersed in a mixture of 400 μL ethanol, 100 μL water, and 40 μL 5% Nafion solution for 20 min to prepare a catalyst dispersion. 5 μL of the catalyst dispersion was drop-coated twice onto a glassy carbon electrode (3 mm in diameter) and allowed to air dry for at least 24 h 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, in a 0.5M aqueous solution of H₂SO₄ saturated with nitrogen or oxygen, a scan rate of 100 mV s⁻¹ was used. -1 Cyclic voltammetry (CV) was used to activate the electrode for 30 min; linear sweep voltammetry (LSV) was used in oxygen-saturated electrolyte at 1.05–1.7 V at 5 mV s. -1 The polarization curves were obtained using the scan rate. Electrochemical impedance spectroscopy (EIS) was performed using a sinusoidal signal with an amplitude of 5 mV at 10... -2 Up to 10 6 Performed within the Hz range.
[0090] The sub-nanometer-sized iridium-oxygen cluster electrocatalyst maintains high efficiency in acidic water splitting to generate oxygen, with an overpotential of 220 mV and a low Tafel slope, demonstrating high stability and good OER performance.
[0091] like Figure 1The XRD pattern of the Ir / NG electrocatalyst prepared in Comparative Example 1 is shown. The 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 crystal is supported on the graphene substrate.
[0092] like Figure 2 The image shows the sub-nano clusters of IrO prepared in Example 1. x W-IrO coupled with a single W atom (W-N3O1) x The XRD pattern of the Ir / NG electrocatalyst shows three distinct diffraction peaks at 40.7°, 47.3°, and 69.1°, belonging to the (111), (200), and (220) crystal planes of Ir, respectively. Compared to Ir / NG, W-IrO x The (111) crystal plane of the / NG electrocatalyst is shifted at a high angle, indicating that the presence of W at high temperature causes W-IrO to... x The lattice structure of / NG is distorted.
[0093] like Figure 3 The image shows the infrared spectrum of the Ir / NG electrocatalyst prepared in Comparative Example 1. As can be seen from the image, the Ir / NG electrocatalyst possesses abundant oxygen functional groups in the range of 3300–2800 cm⁻¹. -1 Absorption of stretching vibrations in the CH region; 2270–2100 cm -1 The characteristic absorption peak for the stretching vibration of the C≡C bond; 1680–1640 cm⁻¹ -1 These are characteristic absorption peaks of the stretching vibrations of unsaturated carbon-carbon bonds (C=C).
[0094] like Figure 4 The image shows the sub-nano clusters of IrO prepared in Example 1. x W-IrO coupled with a single W atom (W-N3O1) x The infrared spectrum of the / NG electrocatalyst shows that the W-IrO x / NG electrocatalysts possess abundant oxygen functional groups, 3469 cm⁻¹ -1 Absorption occurs at 1346 cm⁻¹ due to the stretching vibration of the OH bond. -1 The characteristic absorption peaks for the stretching vibrations of CN are 800–1200 cm⁻¹. -1 The characteristic peaks for the stretching vibration absorption of WO- are shown.
[0095] like Figure 5 The image shows the Raman spectrum of the Ir / NG electrocatalyst prepared in Comparative Example 1, with the D peak at 1348 cm⁻¹. -1 The appearance of the peak () is caused by disordered carbon atoms, and the appearance of the G peak is caused by sp. 2The graph is generated by the in-plane vibrations of carbon atoms; as can be seen from the figure, the D peak, representing carbon atom defects, is the strongest, indicating that the prepared graphene is defect-enriched; the intensity ratio of the D peak to the G peak (I D / I G The value is 0.98.
[0096] like Figure 6 The image shows the W-IrO prepared in Example 1. x Raman spectrum of / NG electrocatalyst, D peak (1348 cm⁻¹) -1 The appearance of the peak () is caused by disordered carbon atoms, and the appearance of the G peak is caused by sp. 2 The graph is generated by the in-plane vibrations of carbon atoms; as can be seen from the figure, the D peak, representing carbon atom defects, is the strongest, indicating that the prepared graphene is defect-enriched; the intensity ratio of the D peak to the G peak (I D / I G The value is 1.02.
[0097] like Figure 7 a and Figure 7 As shown in b, the W-IrO prepared in Example 1 and Comparative Example 1 are respectively. x High-magnification TEM images of both W-IrO₂ and Ir / NG reveal a layered structure with abundant wrinkles and ripples. This morphology facilitates the exposure of more active sites, promoting electrochemical reactions on the surface. x The surface of the W-IrO4 / NG catalyst exhibits a large number of uniform sub-nanometer clusters, with average sizes smaller than those of the undoped Ir / NG electrocatalyst, and no agglomeration is observed. x In / NG, tungsten exists in the form of single atoms, while iridium mainly exists in the form of iridium-oxygen clusters, indicating that tungsten doping induces the formation of iridium-oxygen sub-nanometer clusters under high temperature conditions.
[0098] like Figure 8 a and Figure 8 As shown in b, the W-IrO prepared in Example 1 and Comparative Example 1 are shown. x XPS total spectra and elemental composition diagrams of W-IrO₂ and Ir / NG electrocatalysts. XPS total spectra analysis revealed W-IrO₂... x Both / NG and Ir / NG contain characteristic peaks of C, N, O, and Ir. Among them, W-IrO x The C content of the / NG catalyst is 89.5%, N is 2.47%, O is 6.49%, Ir is 1.07%, and W is 0.47%; the C content of the Ir / NG catalyst is 78.27%, N is 3.89%, O is 16.54%, and Ir is 1.32%.
[0099] like Figure 9 a and Figure 9 As shown in b, the W-IrO prepared in Example 1 and Comparative Example 1 are shown respectively.x XPS fine structure peaks of Ir 4f and W 4f in Ir / NG and Ir / NG electrocatalysts, in Figure 9 Ir can be observed in the fine spectrum of Ir 4f in a. 0 (60.8 and 63.8 eV), Ir 4+ (61.6 and 64.7 eV), tungsten doping did not affect the oxidation state of iridium; Figure 9 b's W-IrO x The negative shift of the WN (32.0 eV) peak in the W4f fine spectrum of / NG by 0.5 eV demonstrates electron transfer between WN species. Furthermore, W-IrO x The increase in WN content in / NG is more pronounced compared to W / NG.
[0100] like Figure 10 The figure shows the performance of the electrocatalysts prepared in Example 1 and Comparative Example 1 in an acidic OER test system on a CH Instruments 760E electrochemical workstation. Figure 10 a and Figure 10 b represents the polarization curve and the corresponding Tafel slope in 0.5MH2SO4 electrolyte, where W-IrO x / NG overpotential (220mV) and Tafel slope (84.9mV dec) -1 Both of these results are superior to Ir / NG, revealing its superior OER performance.
[0101] like Figure 11 As shown, this is the W-IrO prepared in Example 1. x The / NG electrocatalyst was tested for its acidic OER performance in a three-electrode cell system at a CH Instruments 760E electrochemical workstation. Figure 11 a and Figure 11 b represents the CV curves and electrochemical double-layer capacitance (C0) at different scan rates in 0.5 M H2SO4 electrolyte, respectively. dl The W-IrO x / NG catalyst C dl (12.2mF / cm 2 This is mainly due to the increased specific surface area brought about by the sub-nanometer-sized iridium-oxygen clusters induced by tungsten, which leads to enhanced catalytic activity, indicating that W-IrO x / NG electrocatalysts exhibit excellent OER activity.
[0102] like Figure 12 As shown, this is the W-IrO prepared in Example 1. xCurrent galvanostatic testing of / NG electrocatalyst in 0.5M H2SO4 solution (current density 10 mA / cm²) -2 ). At 10mAcm -2 At high current density, W-IrO x The / NG catalyst did not show significant deactivation during 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, Includes the following steps: S1. Add iridium source, tungsten source, and graphene oxide to a mixed solvent consisting of water and anhydrous ethanol to obtain a precursor solution; The pH of the precursor solution was adjusted to 11, and then a solvothermal reaction was carried out to obtain the reaction product. S2. The reaction product was dried and then subjected to high-temperature nitridation using chemical vapor deposition to obtain a sub-nanometer iridium-oxygen cluster electrocatalyst. Wherein, the iridium in the iridium source accounts for 2.5% to 10% of the mass of graphene oxide; and the tungsten in the tungsten source accounts for 2% to 12% of the mass of graphene oxide. The mass-to-volume ratio of the graphene oxide, water, and anhydrous ethanol is 4 mg: 1 mL: 1 mL. In step S1, the temperature of the solvothermal reaction is 160~200℃, and the reaction time is 10~18 h; In step S2, the drying process is freeze-drying, and the freeze-drying time is 2-15 hours. In step S2, the high-temperature nitriding using chemical vapor deposition includes the following steps: nitriding is carried out in a mixed atmosphere of argon and ammonia, with a reaction temperature of 600~1000℃, a reaction time of 1~3 h, an argon flow rate of 100±50 sccm, and an ammonia flow rate of 50±10 sccm.
2. 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 sonicated for 4-8 h to obtain a graphene oxide suspension. Then, an iridium source and a tungsten source are added to the graphene oxide suspension and sonicated for 1-4 h to obtain a precursor solution.
3. The preparation method according to claim 1 or 2, characterized in that, The iridium source is iridium trichloride; the tungsten source is tungsten hexachloride.
4. An electrocatalyst, prepared by any one of claims 1 to 3.
5. The application of the electrocatalyst according to claim 4 as an electrocatalyst for the generation of oxygen in the acidic oxygen evolution reaction.