Ir cluster loaded nano array self-supporting electrode and preparation method and application thereof

Abstract

The invention relates to the field of oxygen evolution electrodes, and discloses an Ir cluster loaded nano array self-supporting electrode and a preparation method and application thereof.The preparation method comprises the steps that a mixed solution of Co (NO3) 2 and Mn (NO3) 2 is prepared, and a conductive substrate is placed in the mixed solution for constant-voltage deposition; then annealing in an air atmosphere; placing the annealed electrode in an iridium tetrachloride solution for dipping; then annealing in an inert atmosphere; and performing acid activation thermal induction on the annealed electrode. According to the invention, carrier structure engineering-monatomic coordination reconstruction-interface stability enhancement is taken as a coordinated regulation path, an ultrathin Co2MnO4 spinel nano array synthesized by developing in-situ self-supporting electro-deposition is taken as a carrier, and unique two-dimensional open structure advantages and an acidic activation-induced directional phase change mechanism are utilized; the invention aims to optimize electron transmission and mass transfer paths and finally realize dynamic balance between'monatomic activity 'and'cluster stability'.

Description

Technical Field

[0001] The present invention relates to the technical field of oxygen evolution electrodes, and in particular to an Ir cluster-loaded nanoarray self-supporting electrode and a preparation method and application thereof. Background Art

[0002] In the field of acidic oxygen evolution reaction (OER) catalysts, the core of proton exchange membrane water electrolysis (PEMWE) technology, iridium-based materials are considered key catalytic components due to their relative stability in strong acid conditions and high oxidation potentials. However, current technology systems face severe challenges in terms of activity, stability, and precious metal utilization. While traditional iridium-based catalysts exhibit considerable OER activity, their mass activity is generally low, and high iridium loadings are required to meet the long-term operation requirements of industrial-scale PEMWEs. To reduce iridium usage, the design concept of single-atom catalysts (SACs) has emerged. By dispersing Ir atoms on a transition metal oxide support, theoretically near-limited atomic utilization can be achieved. For example, patent CN114134533A discloses an oxygen vacancy-anchored iridium single-atom catalyst, its preparation method, and application. However, such systems have exposed multiple technical bottlenecks in engineering applications.

[0003] First, in terms of single-atom loading, the lattice sites of traditional transition metal oxide supports are limited and the surface energy is high, resulting in the maximum loading of Ir single atoms being limited by the accommodation capacity of the crystal structure. Excessive increase in loading will cause atomic aggregation to form low-activity IrO2 nanoparticles, which is fundamentally contradictory to the original design intention of the single-atom catalyst of "high dispersion and high atomic utilization". Secondly, the coordination activity of single atoms is closely related to their local electronic structure, but the Ir single atoms in conventional spinel supports are often bound to rigid oxygen octahedral sites, and their t2g orbital degeneracy is not broken, resulting in the inability to optimize the adsorption energy of oxygen intermediates - for example, excessive O adsorption will increase the reaction energy barrier and cause kinetic hysteresis, while the existing technology has limited improvement in electronic structure through simple doping regulation. Furthermore, the stability problem of single atoms is particularly prominent in acidic OER environments: Co in spinel supports 2+Under strong acid and anodic potential, Ir atoms preferentially dissolve, triggering support lattice collapse and releasing single Ir atoms. These isolated Ir atoms then undergo uncontrollable Ostwald ripening, forming large IrO₂ particles and deactivating the active sites. Furthermore, existing synthesis methods rely on traditional preparation processes, making it difficult to precisely control the embedding depth and spatial distribution of Ir atoms in the support. For example, surface-deposited Ir atoms are completely lost during activation due to a lack of lattice anchoring, while Ir-doped spinels synthesized by traditional methods exhibit unstable oxidation states, leading to continuous collapse of the support structure in acidic media. Finally, the support materials themselves have inherent defects: the irreversible phase transition of transition metal oxides under acidic conditions disrupts the support-active site synergy, while the low conductivity and structural properties of conventional supports limit electron transfer efficiency and the dynamic stability of Ir species, creating a vicious cycle of "support stability-active site retention." Summary of the Invention

[0004] The present invention aims to overcome the above-mentioned problems existing in the iridium-based oxygen evolution catalysts in the prior art, and provides an Ir cluster-loaded nanoarray self-supporting electrode and its preparation method and application. With "support structure engineering-single atom coordination reconstruction-interface stability enhancement" as the synergistic regulation path, the present invention develops ultra-thin Co2MnO4 spinel nanoarrays synthesized by in situ self-supporting electrodeposition as a support, and utilizes its unique two-dimensional open structure advantages and acidic activation-induced directional phase transition mechanism to optimize the electron transport and mass transfer paths, and ultimately achieve a dynamic balance between "single atom activity" and "cluster stability".

[0005] In order to achieve the above object, the present invention adopts the following technical solutions: In a first aspect, the present invention provides a method for preparing an Ir cluster-loaded nanoarray self-supporting electrode, comprising the following steps: (1) Prepare a mixed solution of Co(NO3)2 and Mn(NO3)2, wherein the molar ratio of Co(NO3)2 to Mn(NO3)2 is 2-4:1; add morphology directing agent NH4F and slow-release precipitant urea to the mixed solution, mix well, place a conductive substrate in the mixed solution, and deposit at a constant voltage to make cobalt-manganese layered hydroxide grow in situ on the surface of the conductive substrate, remove it, clean it, and dry it to obtain an electrode; (2) Annealing the electrode in an air atmosphere to form a cobalt-manganese ultra-thin spinel self-supporting electrode; (3) Immerse the annealed electrode in an iridium tetrachloride solution, then take it out and dry it; (4) Annealing the impregnated electrode in an inert atmosphere to form an in-situ self-grown cobalt-manganese spinel catalytic electrode with Ir single atom loading; (5) The annealed electrode is suspended in a sulfuric acid solution for acidic activation thermal induction, and then taken out, cleaned, and dried to obtain the Ir cluster-loaded nanoarray self-supporting electrode.

[0006] This paper addresses the technical bottlenecks of insufficient activity, poor stability, and high iridium loading in iridium-based anode catalysts for proton exchange membrane water electrolysis (PEMWE). By leveraging a coordinated control strategy of "support structure, coordination reconstruction, and interface stabilization," this solution is proposed. This approach utilizes in-situ self-supporting electrodeposition to synthesize ultrathin 2d Co2MnO4 spinel nanoarrays as a support. This, combined with an acidic activation-induced directional phase transition mechanism, allows for the stable anchoring of highly active IrO2 nanoclusters, enabling the construction of a highly efficient oxygen evolution electrode.

[0007] The mechanism of the ultra-thin 2d cobalt-manganese spinel catalyst support of the present invention in optimizing the stability and anchoring sites of IrO2 nanoclusters: In the spinel structure with a specific Co / Mn ratio, Co 2+ preferentially occupying tetrahedral gaps, while Mn 3+ Concentrated in the octahedral gap. 2+ The electronic configuration of Mn 3+ It has stronger metal-oxygen covalency, and the high cobalt content promotes the enhanced hybridization of the lattice oxygen p orbital and the metal d orbital to form a delocalized metal-oxygen covalent network. This strong covalency not only significantly reduces the oxygen vacancy formation energy, but also spontaneously generates high-concentration oxygen vacancies through the local charge compensation mechanism; at the same time, the oxygen vacancies act as electron defect centers, anchoring the iridium precursor through the electrostatic adsorption effect, and ultimately achieving high-density loading of iridium single atoms. At the same time, the ultra-thin two-dimensional nanosheets preferentially expose specific crystal planes, which are composed of alternating Co-O octahedra and Mn-O tetrahedra. The unsaturated coordination state of the surface bridge oxygen sites provides specific anchoring sites for iridium species. During the electrodeposition process, iridium ions are adsorbed on these sites through coordination substitution reactions, and react with adjacent Co 2+ A stable Ir-O-Co heterojunction interface bond is formed. The strong interaction of this interface bond effectively inhibits the migration and aggregation of iridium atoms, ensuring that iridium is evenly dispersed in an isolated single atomic state before activation.

[0008] The mechanism of the stable dynamic reconstruction of surface Ir sites induced by acidic thermal activation is as follows: In an acidic environment, H + Preferentially corrodes Co in the spinel structure 2+ sites, triggering Co selective dissolution and carrier topology reconstruction. This process follows a selective dissolution-recrystallization mechanism: Co 2+ The leaching (thermodynamically spontaneous tendency) leads to the generation of vacancies in the octahedral sites of the spinel crystal, inducing the Mn 3+ The characteristic [MnO6] octahedral tunnel structure of β-MnO2 was reconstructed by Jahn-Teller distortion. 3+Lattice deintercalation causes it to migrate to the support surface, forming a stable Ir-O-Mn tri-coordinate configuration with the bridging oxygen sites of β-MnO2. This strong covalent interaction achieves high-density atomic-level anchoring of Ir species. Under the confinement effect between nanosheet layers, Ir species undergo a unique directed evolution path: the initial monomer grows controllably into sub-nanometer IrO through a deprotonation condensation mechanism. x Clusters, whose size is limited by the interlayer diffusion kinetic barrier. The final formed IrO x / β-MnO2 heterogeneous system achieves synergistic optimization of catalytic performance by balancing the intrinsic activity of atomic-level active sites and the anti-dissolution stability of cluster structures.

[0009] Preferably, in the mixed solution of step (1), the total concentration of metal ions in Co(NO3)2 and Mn(NO3)2 is 0.8~1.2 mol / L; the concentration of the morphology directing agent is 0.1~0.5 mol / L, and the concentration of the slow-release precipitant is 0.1~0.3 mol / L.

[0010] Preferably, the conductive substrate in step (1) is selected from one of carbon cloth, carbon felt, nickel foam, and platinum-coated titanium mesh.

[0011] Preferably, during the constant voltage deposition in step (1), the voltage relative to the Ag / AgCl electrode is -1.0 to -1.2 V, and the deposition time is 5 to 15 minutes.

[0012] Preferably, the annealing temperature in step (2) is 250-350° C., and the annealing time is 1-3 hours.

[0013] Preferably, the concentration of the iridium tetrachloride solution in step (3) is 3-6 mg / mL, and the immersion time is 30-60 min.

[0014] Preferably, the annealing temperature in step (4) is 300-400° C., and the annealing time is 1-3 h.

[0015] Preferably, the concentration of the sulfuric acid solution in step (5) is 0.05-0.1 mol / L; the temperature during the acidic activation heat induction is 60-90°C, the stirring speed is 200-300 rpm, and the time is 18-36 h.

[0016] In a second aspect, the present invention provides an Ir cluster-loaded nanoarray self-supporting electrode prepared by the above-mentioned preparation method.

[0017] In a third aspect, the present invention provides an application of the above-mentioned Ir cluster-loaded nanoarray self-supporting electrode in an oxygen evolution reaction, wherein the reaction is carried out in a single-chamber three-electrode system electrolyzer or a proton exchange membrane electrolyzer; In a single-chamber three-electrode electrolytic cell, the Ir cluster-loaded nanoarray self-supporting electrode is used as the working electrode, a standard Hg / HgSO4 electrode is used as the reference electrode, and a platinum sheet electrode is used as the counter electrode. An electrolyte is injected to perform an electrolytic oxygen evolution reaction at a given potential. In a proton exchange membrane electrolyzer, the Ir cluster-loaded nanoarray self-supporting electrode is used as the anode, and the Pt / C catalyst is loaded on carbon paper as the cathode. The cathode and the anode are placed in the proton exchange membrane electrolyzer, and an electrolyte is injected to perform an electrolytic oxygen evolution reaction at a given potential.

[0018] Therefore, the present invention has the following beneficial effects: (1) The present invention uses cobalt-manganese spinel ultrathin nanoarrays as carriers, which have a unique two-dimensional spinel structure. Its regular atomic arrangement and abundant surface oxygen vacancies provide strong anchoring sites for iridium species. The electronic structure of the iridium active center is optimized through the electronic coupling effect between the metal and the carrier, significantly improving the intrinsic catalytic activity. The high specific surface area characteristics of the two-dimensional nanosheets fully expose the active sites. At the same time, the inherent crystal stability of the spinel can effectively inhibit the corrosion of the carrier in an acidic environment, providing structural support for the long-term stable loading of iridium nanoclusters.

[0019] (2) The in-situ self-supporting electrode of the present invention eliminates the interfacial contact resistance in the traditional powder catalyst coating process by directly growing the nanosheet array on the surface of the conductive substrate, and realizes the vertical penetration of the electron transmission path; the three-dimensional open channels constructed by the ultrathin nanosheets promote the rapid penetration of the electrolyte and the desorption of bubbles, avoiding the shielding effect of the active sites; the self-supporting structure exhibits excellent mechanical stability under high voltage and high current conditions, overcoming the problem of active layer peeling caused by binder degradation in traditional electrodes.

[0020] (3) The present invention adopts an acidic activation thermal induction method, which precisely regulates the evolution of iridium species from single atoms to sub-nanoclusters through the synergistic effect of controllable acid etching and thermodynamic reconstruction; the acidic environment selectively leaches the non-precious metal components in the spinel, and simultaneously induces the reconstruction of the carrier surface to form a highly stable manganese oxide phase, while the thermal drive process promotes the dynamic migration of iridium atoms to form nanoclusters of uniform size; this process reduces the iridium loading while constructing a stable structure with both a highly active Ir-O coordination environment and anti-peroxidation ability, thereby achieving a synergistic improvement in catalytic activity and durability. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 These are SEM images and atomic force microscope images of the electrodes obtained in Example 1 and Comparative Example 1 of the present invention; wherein: a is the SEM image of Comparative Example 1; b is the atomic force microscope image of Comparative Example 1; c is the SEM image of Example 1; d is the atomic force microscope image of Example 1.

[0022] Figure 2 1 and 2 are LSV polarization curves of Examples 1 and 2 of the present invention and Comparative Examples 1 and 3.

[0023] Figure 3 It is a Tafel slope graph of Example 1 of the present invention and Comparative Examples 1 to 3.

[0024] Figure 4 The results of Examples 1-2 and Comparative Examples 1-3 of the present invention are 10 mA / cm 2 and 100 mA / cm 2 Required overpotential diagram.

[0025] Figure 5 It is the mass activity of Example 1 and Comparative Examples 1 to 3 of the present invention in 0.5 mol / L H2SO4 at 2.0 V vs. RHE.

[0026] Figure 6 1 is an X-ray diffraction spectrum of the electrodes obtained in Example 1 and Comparative Examples 1 to 3 of the present invention.

[0027] Figure 7 1 and 2 are energy dispersion spectra of the Co, Mn, O, and Ir elements of the electrodes obtained in Examples 1 and 2 of the present invention.

[0028] Figure 8 TEM images of the electrodes obtained in Example 1 and Comparative Example 1 of the present invention; wherein: (a) is Example 1; (b) is Comparative Example 1.

[0029] Figure 9 These are the ICP-MS analysis results of the electrodes obtained in Example 1 of the present invention and Comparative Example 3.

[0030] Figure 10 This is the 1000mA stability test result of the electrode obtained in Example 1 of the present invention. DETAILED DESCRIPTION

[0031] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0032] In the present invention, unless otherwise specified, all equipment and raw materials can be purchased from the market or are commonly used in the industry. The methods in the following embodiments, unless otherwise specified, are all conventional methods in the art.

[0033] Overall embodiment: A method for preparing an Ir cluster-loaded nanoarray self-supporting electrode comprises the following steps: (1) Prepare a mixed solution of Co(NO3)2 and Mn(NO3)2, wherein the molar ratio of Co(NO3)2 to Mn(NO3)2 is 2~4:1; add morphology directing agent NH4F and slow-release precipitant urea to the mixed solution, mix well, place the conductive substrate in the mixed solution, deposit at constant voltage, remove, clean and dry to obtain an electrode; (2) Annealing the electrode in air atmosphere; (3) Immerse the annealed electrode in an iridium tetrachloride solution, then take it out and dry it; (4) Annealing the impregnated electrode in an inert atmosphere; (5) The annealed electrode is suspended in a sulfuric acid solution for acidic activation thermal induction, and then taken out, cleaned, and dried to obtain the Ir cluster-loaded nanoarray self-supporting electrode.

[0034] As a specific embodiment, in the mixed solution of step (1), the total concentration of metal ions in Co(NO3)2 and Mn(NO3)2 is 0.8~1.2 mol / L; the concentration of the morphology directing agent is 0.1~0.5 mol / L, and the concentration of the slow-release precipitant is 0.1~0.3 mol / L.

[0035] As a specific embodiment, the conductive substrate in step (1) is selected from one of carbon cloth, carbon felt, nickel foam, and platinum-coated titanium mesh.

[0036] As a specific embodiment, in step (1), the conductive substrate is first subjected to acid treatment to remove the surface oxide layer, and then cleaned and dried before being placed in a mixed solution for electrodeposition.

[0037] As a specific embodiment, after constant voltage deposition in step (1), the electrode is taken out and washed alternately with deionized water and anhydrous ethanol 3 to 6 times, and then vacuum dried at 50 to 70°C.

[0038] As a specific embodiment, during constant voltage deposition in step (1), the voltage relative to the Ag / AgCl electrode is -1.0 to -1.2 V, and the deposition time is 5 to 15 minutes.

[0039] As a specific implementation manner, the annealing temperature in step (2) is 250-350° C., and the annealing time is 1-3 hours.

[0040] As a specific implementation manner, the heating rate during annealing in step (2) is 5-20°C / min.

[0041] As a specific embodiment, the concentration of the iridium tetrachloride solution in step (3) is 3-6 mg / mL, and the immersion time is 30-60 min.

[0042] As a specific implementation manner, the annealing temperature in step (4) is 300-400° C., and the annealing time is 1-3 hours.

[0043] As a specific implementation manner, the heating rate during annealing in step (4) is 5-20°C / min.

[0044] As a specific embodiment, the concentration of the sulfuric acid solution in step (5) is 0.05-0.1 mol / L; the temperature during acidic activation heat induction is 60-90°C, the stirring speed is 200-300 rpm, and the time is 18-36 h.

[0045] As a specific embodiment, after the acidic activation heat induction in step (5), the product is taken out, washed alternately with deionized water and ethanol for 3 to 6 times, and vacuum dried at 50 to 70°C.

[0046] Example 1: A method for preparing an Ir cluster-loaded nanoarray self-supporting electrode, comprising the following steps: (1) A platinum-coated titanium mesh with a thickness of 200 μm and a platinum coating of 0.5 μm was selected. Its surface was treated with a 5 wt% oxalic acid solution for 30 minutes to remove the surface oxide layer. Then, it was ultrasonically cleaned with anhydrous ethanol and deionized water for 30 minutes respectively. It was then dried in a vacuum oven for 24 hours. The dried platinum-coated titanium mesh was cut into 4 cm 2 Electrode sheet; (2) Prepare a mixed solution of Co(NO3)2 and Mn(NO3)2, wherein the molar ratio of Co(NO3)2 to Mn(NO3)2 is 3:1; add 0.3 mol / L of morphology directing agent NH4F and 0.2 mol / L of slow-release precipitant urea to the mixed solution, mix well, place the electrode sheet in the mixed solution, and co-deposit at a constant potential of -1.1 V vs Ag / AgCl for 10 minutes; after the deposition is completed, wash the electrode sheet alternately with deionized water and anhydrous ethanol three times, and then dry it in a vacuum oven at 60°C for 12 hours to obtain an electrode; (3) The dried electrode was heated to 250°C in a tube furnace at a heating rate of 5°C / min under air atmosphere and annealed for 2 hours; (4) Immerse the annealed electrode in a 5 mg / mL iridium tetrachloride ethanol solution for 60 min, then take it out and dry it; (5) Place the impregnated electrode in a tube furnace, heat to 350°C at a heating rate of 5°C / min under argon atmosphere, and anneal for 2 hours; (6) The annealed electrode was suspended in 80 mL of 0.05 mol / L sulfuric acid solution and heated at 80 °C with magnetic stirring at 250 rpm for 24 hours for acidic activation thermal induction. After being taken out, the electrode was washed alternately with deionized water and ethanol three times and vacuum dried at 50 °C to obtain the Ir cluster-loaded nanoarray self-supporting electrode. Energy dispersion spectroscopy showed that the Co element content, Mn element content, and Ir element content in the obtained Ir cluster-loaded nanoarray self-supporting electrode were 57.54 wt%, 1.46 wt%, and 1.23 wt%.

[0047] Example 2: A method for preparing an Ir cluster-loaded nanoarray self-supporting electrode, comprising the following steps: (1) A platinum-coated titanium mesh with a thickness of 200 μm and a platinum coating of 0.5 μm was selected. Its surface was treated with a 5 wt% oxalic acid solution for 30 minutes to remove the surface oxide layer. Then, it was ultrasonically cleaned with anhydrous ethanol and deionized water for 30 minutes respectively. It was then dried in a vacuum oven for 24 hours. The dried platinum-coated titanium mesh was cut into 4 cm 2 Electrode sheet; (2) Prepare a mixed solution of Co(NO3)2 and Mn(NO3)2, wherein the molar ratio of Co(NO3)2 to Mn(NO3)2 is 4:1; add 0.3 mol / L of morphology directing agent NH4F and 0.2 mol / L of slow-release precipitant urea to the mixed solution, mix well, place the electrode sheet in the mixed solution, and co-deposit at a constant potential of -1.1 V vs Ag / AgCl for 10 minutes; after the deposition is completed, wash the electrode sheet alternately with deionized water and anhydrous ethanol three times, and then dry it in a vacuum oven at 60°C for 12 hours to obtain an electrode; (3) The dried electrode was heated to 250°C in a tube furnace at a heating rate of 5°C / min under air atmosphere and annealed for 2 hours; (4) Immerse the annealed electrode in a 5 mg / mL iridium tetrachloride ethanol solution for 30 min, then take it out and dry it; (5) Place the impregnated electrode in a tube furnace, heat to 350°C at a heating rate of 5°C / min under argon atmosphere, and anneal for 2 hours; (6) The annealed electrode was suspended in 80 mL of 0.05 mol / L sulfuric acid solution and heated at 80 °C with magnetic stirring at 250 rpm for 24 hours for acidic activation thermal induction. After being taken out, the electrode was washed alternately with deionized water and ethanol three times and vacuum dried at 50 °C to obtain the Ir cluster-loaded nanoarray self-supporting electrode. Energy dispersion spectroscopy showed that the Co element content, Mn element content, and Ir element content in the obtained Ir cluster-loaded nanoarray self-supporting electrode were 54.87 wt%, 1.26 wt%, and 0.96 wt%.

[0048] Example 3: A method for preparing an Ir cluster-loaded nanoarray self-supporting electrode, comprising the following steps: (1) A platinum-coated titanium mesh with a thickness of 200 μm and a platinum coating of 0.5 μm was selected. Its surface was treated with a 5 wt% oxalic acid solution for 30 minutes to remove the surface oxide layer. Then, it was ultrasonically cleaned with anhydrous ethanol and deionized water for 30 minutes respectively. It was then dried in a vacuum oven for 24 hours. The dried platinum-coated titanium mesh was cut into 4 cm 2 Electrode sheet; (2) Prepare a mixed solution of Co(NO3)2 and Mn(NO3)2, wherein the molar ratio of Co(NO3)2 to Mn(NO3)2 is 4:1; add 0.3 mol / L of morphology directing agent NH4F and 0.2 mol / L of slow-release precipitant urea to the mixed solution, mix well, place the electrode sheet in the mixed solution, and co-deposit at a constant potential of -1.1 V vs Ag / AgCl for 10 minutes; after the deposition is completed, wash the electrode sheet alternately with deionized water and anhydrous ethanol three times, and then dry it in a vacuum oven at 60°C for 12 hours to obtain an electrode; (3) The dried electrode was heated to 250°C in a tube furnace at a heating rate of 5°C / min under air atmosphere and annealed for 2 hours; (4) Immerse the annealed electrode in a 5 mg / mL iridium tetrachloride ethanol solution for 10 min, then take it out and dry it; (5) Place the impregnated electrode in a tube furnace, heat to 350°C at a heating rate of 5°C / min under argon atmosphere, and anneal for 2 hours; (6) The annealed electrode was suspended in 80 mL of 0.05 mol / L sulfuric acid solution and heated at 80 °C with magnetic stirring at 250 rpm for 24 hours for acidic activation thermal induction. After being taken out, it was washed alternately with deionized water and ethanol three times and vacuum dried at 50 °C to obtain the Ir cluster-loaded nanoarray self-supporting electrode.

[0049] Comparative Example 1 (commercially available IrO2): A method for preparing an IrO2 loaded electrode, comprising the following steps: (1) A platinum-coated titanium mesh with a thickness of 200 μm and a platinum coating of 0.5 μm was selected. Its surface was treated with a 5 wt% oxalic acid solution for 30 minutes to remove the surface oxide layer. Then, it was ultrasonically cleaned with anhydrous ethanol and deionized water for 30 minutes respectively. It was then dried in a vacuum oven for 24 hours. The dried platinum-coated titanium mesh was cut into 4 cm 2 Electrode sheet; (2) Weigh 75 mg of IrO2 powder (CAS: 12030-49-8, purity 99.95%) and 600 mg of Nafion D520 binder, add 1.5 mL of n-propanol and 1.2 mL of deionized water mixed solvent, ultrasonically disperse for 30 minutes (water bath temperature control <40°C), magnetically stir for 1 hour to prepare a catalytic slurry, use a pipette to draw 20 μL of the slurry and evenly apply it on a platinum-coated titanium mesh, and dry it with hot air at 80°C for 10 minutes to form a 5±1 μm coating; (3) Place the coated electrode in a muffle furnace and heat it to 450℃ at 5℃ / min. Sinter it in air atmosphere for 1 hour. After cooling naturally, immerse it in 0.5mol / L H2SO4 electrolyte. Use platinum as the counter electrode and 10mA / cm 2 The activation was completed by current density constant current polarization for 2 hours to obtain the IrO2 loaded electrode.

[0050] Comparative Example 2 (prepared using slurry coating process): A method for preparing an Ir cluster-loaded electrode, comprising the following steps: (1) A platinum-coated titanium mesh with a thickness of 200 μm and a platinum coating of 0.5 μm was selected and treated with a 5 wt% oxalic acid solution for 30 minutes to remove the oxide layer. The mesh was then ultrasonically cleaned with anhydrous ethanol and deionized water for 30 minutes, dried in a vacuum oven for 24 hours, and cut into 4 cm 2 Spare electrodes; (2) Dissolve 580 mg of Co(NO3)2·6H2O in 20 mL of deionized water containing 30 mg of CTAB to obtain solution A; dissolve 9.08 g of 2-methylimidazole in 140 mL of deionized water to obtain solution B; quickly inject solution A into solution B, stir at room temperature for 60 minutes, collect the purple precipitate by centrifugation, wash it five times with ethanol, and dry it in vacuum at 60°C overnight to obtain nanocrystalline powder; (3) Take 100 mg of the obtained nanocrystal powder, disperse it in 50 mL of deionized water and sonicate to obtain a suspension; dissolve 9.5 mg of Na3IrCl6·xH2O in 10 mL of deionized water, slowly add it to the suspension while stirring, and continue stirring for 3 hours; (4) Centrifuging the mixed solution, collecting the precipitate, washing it twice with deionized water, washing it three times with ethanol, and drying it in a vacuum at 60°C overnight to obtain an Ir exchange precursor; placing this precursor in a crucible, and pyrolyzing it at 300°C in an air atmosphere for 4 hours to obtain a catalyst powder; (5) Take 5 mg of catalyst powder, add 5 mL of anhydrous ethanol and 5 wt% Nafion solution, and ultrasonically treat for 30 minutes to form a uniform catalyst slurry; the catalyst slurry is evenly coated on the electrode substrate, dried and solidified at 60°C to obtain the Ir cluster loaded electrode.

[0051] Comparative Example 3 (without acidic activation heat induction): A method for preparing an Ir cluster-loaded nanoarray self-supporting electrode, comprising the following steps: (1) A platinum-coated titanium mesh with a thickness of 200 μm and a platinum coating of 0.5 μm was selected. Its surface was treated with a 5 wt% oxalic acid solution for 30 minutes to remove the surface oxide layer. Then, it was ultrasonically cleaned with anhydrous ethanol and deionized water for 30 minutes respectively. It was then dried in a vacuum oven for 24 hours. The dried platinum-coated titanium mesh was cut into 4 cm 2 Electrode sheet; (2) Prepare a mixed solution of Co(NO3)2 and Mn(NO3)2, wherein the molar ratio of Co(NO3)2 to Mn(NO3)2 is 3:1; add 0.3 mol / L of morphology directing agent NH4F and 0.2 mol / L of slow-release precipitant urea to the mixed solution, mix well, place the electrode sheet in the mixed solution, and co-deposit at a constant potential of -1.1 V vs Ag / AgCl for 10 minutes; after the deposition is completed, wash the electrode sheet alternately with deionized water and anhydrous ethanol three times, and then dry it in a vacuum oven at 60°C for 12 hours to obtain an electrode; (3) The dried electrode was heated to 250°C in a tube furnace at a heating rate of 5°C / min under air atmosphere and annealed for 2 hours; (4) Immerse the annealed electrode in a 5 mg / mL iridium tetrachloride ethanol solution for 60 min, then take it out and dry it; (5) The impregnated electrode was placed in a tube furnace, heated to 350°C at a heating rate of 5°C / min under an argon atmosphere, and annealed for 2 hours to obtain the Ir cluster-loaded nanoarray self-supporting electrode.

[0052] The electrodes prepared in the above examples and comparative examples were applied to a proton exchange membrane electrolyzer to perform electrolytic oxygen evolution reaction, and the performance of the catalyst was tested. The specific method is as follows: (1) The electrodes prepared in the above examples and comparative examples were used as anode gas diffusion electrodes (GDEs) of PEM electrolyzers; (2) First, 20 mg of Pt / C catalyst was dispersed in 2 mL of isopropanol and ultrasonicated for 30 min. Then, 40 μL of 5 wt% Nafion solution was added and ultrasonicated for 30 min to obtain a uniform ink. The ink was then sprayed onto the hydrophobic surface of carbon paper to obtain a Pt / C loading of 0.8 mg cm -2 A cathode gas diffusion electrode; (3) A 5 wt% Nafion solution was sprayed on the anode side of the Nafion 115 membrane, and then the anode gas diffusion electrode and the cathode gas diffusion electrode were pressed on both sides of the Nafion 115 membrane at 130 °C for 3 minutes to obtain a membrane electrode; finally, the constructed membrane electrode was assembled onto a bipolar plate and tested for water electrolysis.

[0053] The electrodes prepared in Example 1 and Comparative Example 1 were characterized by SEM and atomic force microscopy. Figure 1 As shown in the figure, it can be seen that the vertical array of electrode nanosheets prepared by the method of the present invention in Example 1 forms micron-scale channels (pore diameter of about 50 nm), and the average thickness of the nanosheets is about 1.25 nm, while the average thickness of the electrode prepared by commercially available IrO2 in Comparative Example 1 is above 1.5 nm, and the average roughness is 0.426 nm.

[0054] from Figures 2 to 4 As can be seen from the linear sweep voltammetry (LSV) test, the electrode in Example 1 has a -2 The oxygen evolution overpotential is 218-225 mV (vs. RHE) and the Tafel slope is 39.6 mV / dec, reaching 100 mA cm -2 The required overpotential is 437 mV, which is significantly lower than that of the traditional IrO2 catalyst in Comparative Example 1.

[0055] from Figure 5 As can be seen from the results, the mass activity of Ir in Example 1 is 2974.24 A g -1 (1.53 V vs. RHE), compared with the conventional slurry coating process in Comparative Example 2 (1228.8 A g -1 ) has improved significantly.

[0056] like Figure 6 and Figure 7 As shown in , in the embodiment, the Ir doping amount (0.5-1.2 wt%) is precisely controlled by the immersion adsorption-thermal acid activation method, and the Ir clusters are evenly distributed on the electrode surface without affecting the face-centered cubic structure of the cobalt-manganese spinel. Figure 8 The TEM results show that the average lattice spacing in Example 1 is 0.289 nm, which is larger than that in Comparative Example 1, which is conducive to the exposure of active sites.

[0057] like Figure 9 As shown in Figure 1, the Ir dissolution rate of the activated support in Example 1 was <0.02 μg h-1 under acidic conditions of 1.8 V (vs. RHE). -1 cm -2 (ICP-MS), compared with the electrode without activation in Comparative Example 3 (0.055 μg h-1 cm -2 ) is reduced by 69%. As shown in Figure 10, Example 1 has a -2 In the constant current test, the voltage decay rate is only 0.015 mV h -1 (Total decay <15 mV after 100 hours).

[0058] At the same time, the present invention replaces the pure Ir-based carrier with Co2MnO4, and the amount of precious metal Ir is reduced to 0.15-0.3 mg cm -2 , compared with traditional IrO2 (2-4 mg cm -2 ) is reduced by 92-96%. Based on the current prices of Ir (120 million yuan / ton) and Co (230,000 yuan / ton), the cost of the anode catalyst of this invention is only 1 / 40-1 / 30 of that of traditional solutions.

[0059] It should be noted that the specific implementation method described above provides a detailed description of the technical solutions and application results of the present invention. The above embodiments are only the most preferred embodiments and are not intended to limit the present invention. Modifications or equivalent replacements made by relevant technical personnel within the core theoretical scope of the present invention should all fall within the scope of protection of the present invention.

Claims

1. A method for preparing an Ir cluster-loaded nanoarray self-supporting electrode, characterized in that: The steps include: (1) Prepare a mixed solution of Co(NO3)2 and Mn(NO3)2, wherein the molar ratio of Co(NO3)2 to Mn(NO3)2 is 2~4:1; add morphology directing agent NH4F and slow-release precipitant urea to the mixed solution, mix well, place the conductive substrate in the mixed solution, deposit at constant voltage, remove, clean and dry to obtain an electrode; (2) Annealing the electrode in air atmosphere; (3) Immerse the annealed electrode in an iridium tetrachloride solution, then take it out and dry it; (4) Annealing the impregnated electrode in an inert atmosphere; (5) The annealed electrode is suspended in a sulfuric acid solution for acidic activation thermal induction, and then taken out, cleaned, and dried to obtain the Ir cluster-loaded nanoarray self-supporting electrode.

2. The method for preparing the Ir cluster-loaded nanoarray self-supporting electrode according to claim 1, wherein: In the mixed solution of step (1), the total concentration of metal ions in Co(NO3)2 and Mn(NO3)2 is 0.8~1.2 mol / L; the concentration of the morphology directing agent is 0.1~0.5 mol / L, and the concentration of the slow-release precipitant is 0.1~0.3 mol / L.

3. The method for preparing the Ir cluster-loaded nanoarray self-supporting electrode according to claim 1, wherein: The conductive substrate described in step (1) is selected from one of carbon cloth, carbon felt, nickel foam, and platinum-coated titanium mesh.

4. The method for preparing the Ir cluster-loaded nanoarray self-supporting electrode according to claim 1, 2 or 3, wherein: During constant voltage deposition in step (1), the voltage relative to the Ag / AgCl electrode is -1.0 to -1.2 V, and the deposition time is 5 to 15 minutes.

5. The method for preparing the Ir cluster-loaded nanoarray self-supporting electrode according to claim 4, wherein: The annealing temperature in step (2) is 250-350°C, and the annealing time is 1-3 hours.

6. The method for preparing the Ir cluster-loaded nanoarray self-supporting electrode according to claim 1, wherein: The concentration of the iridium tetrachloride solution in step (3) is 3-6 mg / mL, and the immersion time is 30-60 min.

7. The method for preparing the Ir cluster-loaded nanoarray self-supporting electrode according to claim 1, wherein: The annealing temperature in step (4) is 300-400°C, and the annealing time is 1-3 hours.

8. The method for preparing the Ir cluster-loaded nanoarray self-supporting electrode according to claim 1, wherein: The concentration of the sulfuric acid solution in step (5) is 0.05-0.1 mol / L; the temperature during the acidic activation heat induction is 60-90°C, the stirring speed is 200-300 rpm, and the time is 18-36 h.

9. An Ir cluster-loaded nanoarray self-supporting electrode, characterized in that: The method is prepared according to any one of claims 1 to 8.

10. Use of the Ir cluster-loaded nanoarray self-supporting electrode according to claim 9 in oxygen evolution reaction, characterized in that: The reaction is carried out in a single-chamber three-electrode system electrolyzer or a proton exchange membrane electrolyzer; In a single-chamber three-electrode electrolytic cell, the Ir cluster-loaded nanoarray self-supporting electrode is used as the working electrode, a standard Hg / HgSO4 electrode is used as the reference electrode, and a platinum sheet electrode is used as the counter electrode. An electrolyte is injected to perform an electrolytic oxygen evolution reaction at a given potential. In a proton exchange membrane electrolyzer, the Ir cluster-loaded nanoarray self-supporting electrode is used as the anode, and the Pt / C catalyst is loaded on carbon paper as the cathode. The cathode and the anode are placed in the proton exchange membrane electrolyzer, and an electrolyte is injected to perform an electrolytic oxygen evolution reaction at a given potential.

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