A transition metal-doped iridium-based nanomaterial, a preparation method and application thereof

Abstract

The application discloses a transition metal doped iridium-based nanomaterial and a preparation method and application thereof, and belongs to the technical field of nanometer scale inorganic metal material synthesis. The preparation method of the transition metal doped iridium-based nanomaterial provided by the application adopts a molten salt synthesis method, an iridium salt compound doped with a transition metal is prepared, the iridium salt compound is calcined to obtain iridium oxide doped with the transition metal, and finally the iridium oxide doped with the transition metal is reduced through high-temperature heat treatment to prepare the transition metal doped iridium-based nanomaterial. The preparation method is simple and easy to implement, green and safe, and has a high yield; under the premise of doping a small amount of transition metal, the inherent electrocatalytic activity of the iridium-based nanomaterial is improved. Moreover, the transition metal doped iridium-based nanomaterial obtained by using the preparation method has a wide application prospect in the industrialized water electrolysis of a proton exchange membrane water electrolysis cell.

Description

Technical Field

[0001] This invention relates to the field of nanoscale inorganic metal material synthesis technology, and in particular to a transition metal-doped iridium-based nanomaterial, its preparation method, and its application. Background Technology

[0002] Hydrogen energy, with its advantages of being clean, sustainable, and having low energy density, is currently considered a promising alternative to fossil fuels. Electrolysis of water to produce hydrogen is one of the core technologies of future energy systems. Electrochemical water splitting consists of two half-reactions: the hydrogen evolution reaction (HER) at the cathode and the oxygen evolution reaction (OER) at the anode. Related electrolysis technologies can be mainly divided into three categories: proton exchange membrane (PEM) electrolyzers, alkaline water electrolyzers (AWE), and solid oxide electrolyzers (SOE). PEM electrolyzers have higher proton conductivity, lower gas crosstalk, higher efficiency, and shorter response time, making them more suitable for integration with intermittent renewable energy sources. However, because the anode of a PEM electrolyzer is in a strongly acidic environment, the requirement for electrode corrosion stability is very high, limiting the range of catalytic materials that can be selected for the HER and OER reactions at the cathode and anode.

[0003] Currently, only noble metal-based catalysts (Pt for HER and Ir for OER) exhibit acceptable acid resistance and catalytic activity for commercially used PEM electrolyzers. In recent years, various catalysts for acidic OER have been developed; however, limited by the inverse relationship between catalytic activity and stability, only iridium-based catalysts have shown stable catalytic activity as OER catalysts for PEM electrolyzers. However, their production process is difficult to control, resulting in low yields, high product prices, and limited sustainability. Summary of the Invention

[0004] In view of this, the technical problem to be solved by the present invention is to provide a transition metal-doped iridium-based nanomaterial, its preparation method, and its application. The preparation method of the transition metal-doped iridium-based nanomaterial adopts a molten salt synthesis method, which is simple, easy to implement, green, safe, and has a high yield. Under the premise of doping with a small amount of transition metal, the inherent electrocatalytic activity of the iridium-based nanomaterial is improved.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] This invention provides a method for preparing transition metal-doped iridium-based nanomaterials, comprising the following steps:

[0007] 1) Mix iridium source, transition metal source, salt and alcohol solvent evenly and react to obtain transition metal-doped iridium salt compound;

[0008] 2) The above-mentioned transition metal-doped iridium salt compound was calcined to obtain transition metal-doped iridium oxide;

[0009] 3) The transition metal-doped iridium oxide was subjected to high-temperature heat treatment under a reducing atmosphere to prepare transition metal-doped iridium-based nanomaterials.

[0010] The above preparation method uses molten salt synthesis to prepare transition metal-doped iridium salt compounds, which are then calcined to obtain transition metal-doped iridium oxide. Finally, the transition metal-doped iridium oxide is further reduced by high-temperature heat treatment to prepare transition metal-doped iridium-based nanomaterials.

[0011] Preferably, in step 1), the iridium source is selected from one or more of chloroiridium acid, iridium acetylacetonate, iridium chloride, potassium chloroiridate, sodium chloroiridate, and iridium acetate; more preferably, the iridium source is selected from one or more of chloroiridium acid, iridium acetylacetonate, and iridium chloride; and even more preferably, chloroiridium acid.

[0012] Preferably, the transition metal source is selected from one or more of iron, cobalt, and nickel sources.

[0013] Preferably, the iron source is selected from one or more of iron pentacarbonyl, iron acetylacetone, and iron nitrate nonahydrate.

[0014] Preferably, the cobalt source is selected from one or more of cobalt acetylacetonate, cobalt chloride hexahydrate, and cobalt nitrate hexahydrate.

[0015] Preferably, the nickel source is selected from one or more of nickel acetate tetrahydrate, nickel acetylacetonate, and nickel chloride hexahydrate; more preferably, it is nickel chloride hexahydrate.

[0016] Preferably, the salt is selected from alkali metal salts or ammonium salts.

[0017] Preferably, the alkali metal salt is selected from one or more of potassium carbonate, potassium nitrate, potassium sulfate, potassium chloride, sodium nitrate, sodium carbonate, sodium chloride, and sodium sulfate; more preferably, it is selected from potassium carbonate, potassium nitrate, potassium sulfate, potassium chloride, and sodium nitrate. In some specific embodiments of the present invention, the alkali metal salt is preferably sodium nitrate.

[0018] Preferably, the ammonium salt is selected from one or more of ammonium chloride, ammonium nitrate, ammonium carbonate, and ammonium sulfate.

[0019] Preferably, the alcohol solvent is selected from one or more of ethanol, ethylene glycol, isopropanol, and glycerol; more preferably, it is selected from one or more of ethanol, ethylene glycol, and isopropanol; and even more preferably, it isopropanol.

[0020] In the above preparation method, iridium-based nanomaterials with different transition metal doping amounts were prepared by using iridium source and transition metal source in different proportions.

[0021] Preferably, in step 1), the mass ratio of the iridium source to the transition metal source is (10-50):1; more preferably, it is 50:1, 20:1, or 10:1. In some specific embodiments of the present invention, the transition metal-doped iridium-based nanomaterials are respectively represented as IrNi. 0.02 IrNi 0.05 IrNi 0.1 .

[0022] Preferably, the mass ratio of the iridium source to the salt is 1:(5-20); more preferably, it is 1:(10-15). In some specific embodiments of the present invention, the mass ratio of the iridium source to the salt is preferably 1:10.

[0023] Preferably, the concentration of the iridium source in the alcohol solvent is 1–10 mg / mL; more preferably, it is 2–8 mg / mL. In some specific embodiments of the present invention, the concentration of the iridium source in the alcohol solvent is preferably 2 mg / mL.

[0024] Preferably, the reaction temperature is 60°C to 90°C; more preferably 70°C to 80°C; and even more preferably 70°C.

[0025] Preferably, in step 1), a surfactant or complexing agent is added to the reaction system. Adding a surfactant or complexing agent promotes the reaction to obtain uniformly dispersed transition metal-doped iridium-based nanomaterials.

[0026] Preferably, the surfactant is selected from one or more of polyvinylpyrrolidone (PVP), hexadecyltrimethylammonium bromide (CTAB), and sodium dodecyl sulfate (SDS). In some specific embodiments of the present invention, PVP is preferred.

[0027] Preferably, the molar ratio of the surfactant to the iridium source is (0-1):10; more preferably (0-0.5):10; and even more preferably 0.4:10.

[0028] Preferably, the calcination temperature in step 2) of this invention is 300℃~500℃; more preferably, it is 350℃~450℃; in some specific embodiments of this invention, it is preferably 400℃.

[0029] Preferably, the calcination time is 1 to 5 hours; more preferably, it is 2 hours.

[0030] Preferably, after the calcination in step 2) is completed, the present invention further includes centrifugal separation, washing, and drying post-treatment.

[0031] The present invention does not specifically limit the above-mentioned centrifugal separation method, and can be a centrifugal method well known to those skilled in the art, such as differential centrifugation, density gradient centrifugation, sedimentation equilibrium centrifugation, etc.

[0032] The present invention does not have any particular limitation on the solvent used for the above washing, and can be any washing solvent known to those skilled in the art.

[0033] In this invention, the solvent used for washing is preferably deionized water and anhydrous ethanol.

[0034] The present invention does not specifically limit the above-mentioned drying method, and can be a drying method well known to those skilled in the art, such as vacuum drying, oven drying, atmospheric pressure drying, freeze drying, etc.

[0035] In this invention, the drying is preferably performed using vacuum drying.

[0036] Preferably, the vacuum drying temperature is 40°C to 80°C; more preferably, it is 50°C to 70°C. In some specific embodiments of the present invention, 70°C is preferred.

[0037] Preferably, the vacuum drying time is 4 to 12 hours; more preferably, it is 8 to 12 hours.

[0038] After the above drying process is completed, the obtained transition metal-doped iridium oxide is further reduced at high temperature to prepare transition metal-doped iridium-based nanomaterials.

[0039] Preferably, in step 3), the reducing atmosphere is selected from a hydrogen-argon mixture or argon gas.

[0040] Preferably, the hydrogen content in the hydrogen-argon mixture is 1 wt% to 3 wt%.

[0041] Preferably, the high-temperature heat treatment temperature is 300℃ to 600℃; more preferably, it is 400℃ to 500℃. In some specific embodiments of the present invention, 500℃ is preferred.

[0042] Preferably, the high-temperature heat treatment time is 1 to 5 hours; more preferably, it is 1 to 3 hours.

[0043] The preparation method described in this invention uses a simple and easy molten salt synthesis method to obtain transition metal-doped iridium salt compounds, and further calcines and oxidizes the product and reduces it by high-temperature heat treatment, finally preparing iridium-based nanomaterials doped with a small amount of transition metal.

[0044] This invention involves doping iridium-based nanomaterials with a small amount of transition metal. The transition metal atoms can adjust the d-band structure of the iridium surface, and based on short-range electronic interactions or long-range geometric strain effects, the electrocatalytic activity of iridium-based nanomaterials is greatly improved with the addition of a small amount of transition metal.

[0045] The present invention also provides a transition metal-doped iridium-based nanomaterial, which is prepared by the above-described preparation method.

[0046] The molten salt synthesis method described above is beneficial to crystal growth, enabling transition metal-doped iridium-based nanomaterials to have good microstructures.

[0047] Preferably, the particle size of the transition metal-doped iridium-based nanomaterial is 20–30 nm.

[0048] The transition metal-doped iridium-based nanomaterials described in this invention exhibit high OER catalytic activity.

[0049] The present invention also provides the application of transition metal-doped iridium-based nanomaterials prepared by the above preparation method or the application of the above transition metal-doped iridium-based nanomaterials in the anodic reaction of water electrolysis.

[0050] Preferably, the transition metal-doped iridium-based nanomaterials can be well applied in proton exchange membrane water electrolysis processes as catalysts for the acidic oxygen evolution reaction.

[0051] The present invention also provides a method for electrolyzing water, using transition metal-doped iridium-based nanomaterials prepared by the above preparation method or the above transition metal-doped iridium-based nanomaterials as catalysts.

[0052] This invention does not impose any special limitations on other conditions and reactions of the above-mentioned water electrolysis method; the transition metal-doped iridium-based nanomaterials described in this invention can be used as catalysts.

[0053] Compared with existing technologies, the method for preparing transition metal-doped iridium-based nanomaterials provided by this invention employs a molten salt synthesis method to prepare transition metal-doped iridium salt compounds, which are then calcined to obtain transition metal-doped iridium oxide. Finally, the transition metal-doped iridium oxide is reduced by high-temperature heat treatment to obtain transition metal-doped iridium-based nanomaterials. This preparation method is simple, safe, and yields high efficiency. It enhances the inherent electrocatalytic activity of iridium-based nanomaterials while doping with a small amount of transition metal. Furthermore, the transition metal-doped iridium-based nanomaterials have broad application prospects in industrial PEM water electrolysis. Attached Figure Description

[0054] Figure 1 IrNi is an iridium-based nanomaterial doped with nickel, a transition metal. 0.02 X-ray diffraction (XRD) pattern;

[0055] Figure 2 IrNi is an iridium-based nanomaterial doped with nickel, a transition metal. 0.02Transmission electron microscope (TEM) image of nanomaterials;

[0056] Figure 3 Transmission electron microscopy (TEM) image of IrNi0, an iridium-based nanomaterial without transition metal doping.

[0057] Figure 4 A comparison of the electrochemical oxygen evolution polarization curves of iridium-based nanocatalysts with different nickel doping amounts, IrNi0, and commercial IrO2 catalysts in sulfuric acid solution;

[0058] Figure 5 IrNi is an iridium-based nanomaterial doped with nickel, a transition metal. 0.02 A performance comparison chart of nanocatalysts and iridium-based nanocatalysts without transition metal doping used in PEM electrolysis devices. Detailed Implementation

[0059] To further illustrate the present invention, the following detailed description of the transition metal-doped iridium-based nanomaterials, their preparation methods, and applications provided by the present invention is provided in conjunction with embodiments.

[0060] Example 1

[0061] (I) Synthesis of Iridium-based Nanomaterials Doped with Transition Metals

[0062] The mass ratio of iridium source to nickel source is controlled at 50:1 (IrNi x (x = 0.02), weigh 100 mg of chloroiridic acid, 2 mg of nickel chloride hexahydrate, 1 g of sodium nitrate, and 4 mg of surfactant PVP (PVP to chloroiridic acid mass ratio of 0.4:10), and add them sequentially to 50 mL of isopropanol solution. Stir at room temperature until the mixture is homogeneous to obtain a mixed solution.

[0063] The resulting mixed solution was placed in a 100 mL beaker and heated in an oil bath with stirring at 70 °C. After evaporating the solution to dryness, a nickel-doped iridium salt compound was obtained. The resulting product was ground and calcined in a muffle furnace at 400 °C for 2 h. Then, the further obtained product was centrifuged, washed, and dried in a vacuum oven at 70 °C for 12 h to obtain iridium oxide (IrNi) doped with a transition metal. 0.02 O2 was used to prepare nickel-doped iridium-based nanomaterials by heat treatment at 500°C for 1 hour in a tube furnace under a hydrogen-argon mixed atmosphere (hydrogen content of 1wt%–3wt%). The nickel-doped iridium-based nanomaterials prepared above were then characterized. Figure 1 For IrNi 0.02 XRD pattern of the material. Figure 2 For IrNi 0.02 TEM images of the material show that the transition metal nickel-doped iridium-based nanomaterial IrNi0.02 It is in the form of nanoparticles with a size of 20–30 nm.

[0064] Examples 2-3

[0065] Besides changing the mass ratio of iridium to nickel (IrNi) x (x = 0.05, 0.1), other methods and conditions are the same as in Implementation Case 1, and finally, IrNi, a transition metal nickel-doped iridium-based nanomaterial, is prepared. 0.05 and IrNi 0.1 .

[0066] Comparative Example 1

[0067] Synthesis of Iridium-based Nanomaterials without Transition Metal Doping

[0068] Weigh 100 mg of chloroiridic acid, 1 g of sodium nitrate, and 4 mg of surfactant PVP (PVP to chloroiridic acid mass ratio of 0.4:10), and add them sequentially to 50 mL of isopropanol solution. Stir and mix thoroughly at room temperature to obtain a mixed solution.

[0069] The resulting mixed solution was placed in a 100 mL beaker and heated in an oil bath with stirring at 70 °C. After the reaction was complete, the solution was evaporated to dryness to obtain an iridium salt compound without transition metal doping. The obtained product was ground and calcined in a muffle furnace at 400 °C for 2 h. Then, the further obtained product was centrifuged, washed, and dried in a vacuum oven at 70 °C for 12 h to obtain iridium oxide (IrO2) without transition metal doping. Finally, it was heat-treated in a tube furnace at 500 °C for 1 h in a hydrogen-argon mixed atmosphere (hydrogen content of 1 wt% to 3 wt%) to obtain iridium-based nanomaterials (IrNi0) without transition metal doping. Figure 3 This is a TEM image of iridium-based nanomaterials without transition metal doping.

[0070] Performance testing experiment

[0071] (I) OER Performance Testing

[0072] Data was collected using a CHI660e electrochemical workstation. Examples 1-3 (IrNi) were compared with those above. 0.02 IrNi 0.05 IrNi 0.1The nanomaterials prepared by Example 1 (IrNi0) and Comparative Example 2 (IrNi0) were used as catalysts for the oxygen evolution reaction in an acidic environment. A three-electrode testing system was used, with a carbon rod as the counter electrode and a silver / silver chloride electrode as the reference electrode. 5 mg of the above nanocatalysts were weighed and dispersed in a mixed solvent containing 1 mL of water and 1 mL of isopropanol (V1:V2 = 1:1). The dispersion was ultrasonically adjusted to obtain a uniformly dispersed slurry. A certain amount was uniformly drop-coated onto a 5 mm diameter Au electrode as the working electrode and allowed to air dry naturally. The loading was 0.25 mg / cm³. 2 For testing purposes, a 0.5M sulfuric acid solution was selected as the electrolyte.

[0073] Activity testing: Electrochemical data (LSV) were measured using linear sweep voltammetry at a scan rate of 5 mV / s, with a test voltage range of 0.9–1.6 V vs. RHE. Several tests were performed until the data stabilized, and the final result was used. Under the same conditions, the OER performance of commercial IrO2 was tested for comparison.

[0074] Experimental results:

[0075] Figure 4 For IrNi 0.02 IrNi 0.05 IrNi 0.1 The OER catalytic performance comparison chart between IrNi0 and commercial IrO2 is shown in the figure. The test results are as follows: Figure 4 As shown. LSV results indicate that, compared to undoped transition metal iridium-based nanocatalysts IrNiO and commercial IrO2, the nickel-doped IrNiO prepared in this invention... 0.02 IrNi 0.05 IrNi 0.1 Nanocatalysts exhibit higher catalytic activity. Among them, the OER catalytic activity, from highest to lowest, is IrNi. 0.02 IrNi 0.05 IrNi 0.1 IrNiO, commercial IrO2.

[0076] (II) Membrane Electrode Fabrication and Testing

[0077] The IrNi prepared above 0.02 The IrNiO nanocatalyst was tested in a PEM water electrolysis device using a two-electrode method. The cathode used a commercially available platinum-carbon catalyst for the hydrogen evolution reaction, while the anode used the IrNiO nanocatalyst prepared in this invention. 0.02 Using IrNiO nanocatalysts for the oxygen evolution reaction, the catalysts from both the anode and cathode were fabricated into membrane electrodes using a spray-coating-transfer pressing method. The catalyst loading at the anode was 0.5 mg. Ir / cm 2 They are assembled into PEM devices. For example... Figure 5 As shown, IrNi prepared using the present invention 0.02 When used as a catalyst, at 1 A / cm 2 At current density, its potential is 1.716V, and at 2A / cm²... 2 At the current density, its potential is 1.901V.

[0078] The results show that the IrNi prepared by this invention 0.02 The nanocatalyst exhibited superior catalytic performance in PEM testing, with its OER catalytic activity and mass activity significantly exceeding those of the currently undoped transition metal-based iridium nanocatalyst IrNi0. This indicates that IrNi... 0.02 Nanocatalysts hold promise as anodic oxygen evolution catalysts for PEM water electrolysis to produce hydrogen.

[0079] In summary, the preparation method described in this invention is simple and easy to implement, and significantly improves the inherent electrocatalytic activity of iridium-based nanomaterials by doping with a small amount of transition metal. The transition metal-doped iridium-based nanomaterials prepared by this invention exhibit high OER activity, improving catalytic activity and reducing catalyst cost under the premise of low loading of noble metal Ir, and are expected to realize the application of low-iridium OER catalysts in the field of PEM water electrolysis for hydrogen production.

[0080] The above description of the embodiments is only for the purpose of helping to understand the method and core ideas of the present invention. It should be noted that those skilled in the art can make several improvements and modifications to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

Claims

1. A method for preparing a transition metal-doped iridium-based nanomaterial, characterized in that, The method comprises the following steps: 1) mixing an iridium source, a transition metal source, a salt and an alcohol solvent uniformly and reacting to obtain a transition metal-doped iridium salt compound; 2) calcining the transition metal-doped iridium salt compound to obtain a transition metal-doped iridium oxide; 3) high-temperature heat treating the transition metal-doped iridium oxide under a reducing atmosphere to obtain a transition metal-doped iridium-based nanomaterial; The iridium source in the step 1) is selected from one or more of chloroiridic acid, iridium acetylacetonate, iridium chloride, potassium chloroiridate, sodium chloroiridate and iridium acetate; The transition metal source is selected from one or more of an iron source, a cobalt source and a nickel source; The iron source is selected from one or more of iron pentacarbonyl, iron acetylacetonate and iron nitrate nonahydrate; The cobalt source is selected from one or more of cobalt acetylacetonate, cobalt chloride hexahydrate and cobalt nitrate hexahydrate; The nickel source is selected from one or more of nickel acetate tetrahydrate, nickel acetylacetonate and nickel chloride hexahydrate; The salt is selected from an alkali metal salt or an ammonium salt; The alkali metal salt is selected from one or more of potassium carbonate, potassium nitrate, potassium sulfate, potassium chloride, sodium nitrate, sodium carbonate, sodium chloride and sodium sulfate; The ammonium salt is selected from one or more of ammonium chloride, ammonium nitrate, ammonium carbonate and ammonium sulfate; The mass ratio of the iridium source to the transition metal source in the step 1) is (10-50):1; The mass ratio of the iridium source to the salt is 1:(5-20); The reaction temperature is 60-90℃.

2. The method for preparing transition metal-doped iridium-based nanomaterials according to claim 1, characterized in that, The alcohol solvent is selected from one or more of ethanol, ethylene glycol, isopropyl alcohol and glycerol.

3. The method for preparing transition metal-doped iridium-based nanomaterials according to claim 1, characterized in that, The concentration of the iridium source in the alcohol solvent is 1-10 mg / mL.

4. The method for preparing transition metal-doped iridium-based nanomaterials according to claim 1, characterized in that, The system in the step 1) is additionally added with a surfactant or a complexing agent.

5. The method for preparing transition metal-doped iridium-based nanomaterials according to claim 1, characterized in that, The calcination temperature in the step 2) is 300-500℃; The calcination time is 1-5 h.

6. The method for preparing transition metal-doped iridium-based nanomaterials according to claim 1, characterized in that, The step 2) further comprises centrifugal separation, washing and drying after-treatment after the calcination is completed.

7. The method for preparing transition metal-doped iridium-based nanomaterials according to claim 1, characterized in that, The reducing atmosphere in the step 3) is selected from hydrogen-argon mixed gas; The hydrogen content in the hydrogen-argon mixed gas is 1-3 wt%; The high-temperature heat treating temperature is 300-600℃; The high-temperature heat treating time is 1-5 h.

8. A transition metal doped iridium based nanomaterial, characterized in that, Prepared by the preparation method in any one of claims 1-7; The particle size of the transition metal-doped iridium-based nanomaterial is 20-30 nm.

9. Application of the transition metal-doped iridium-based nanomaterial prepared by the preparation method in any one of claims 1-7 or the transition metal-doped iridium-based nanomaterial in claim 8 in anodic reaction of water electrolysis.

10. A method of electrolyzing water, characterized by, The transition metal-doped iridium-based nanomaterial prepared by the preparation method in any one of claims 1-7 or the transition metal-doped iridium-based nanomaterial in claim 8 is used as a catalyst.

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