Modified ruthenium-based acidic oxygen evolution catalyst as well as preparation method and application thereof

Abstract

The invention discloses a modified ruthenium-based acidic oxygen evolution catalyst as well as a preparation method and application thereof, and belongs to the technical field of nano materials and catalysis. The preparation method comprises the following steps: firstly, mixing a mixed solution of transition metal salt and soluble ruthenium salt with a complex ligand dispersion liquid, then evaporating and curing to obtain a metal chelate precursor, and finally performing pyrolysis oxidation to obtain the metal chelate. The transition metal salt comprises at least one of soluble Nb, Ti, Cr, Mn, Co, Cd, Sn and Sb metal salts. The preparation process is simple and easy to implement, the precursor salt is flexible to select, the synthesis method has high expansibility in preparation of the nano oxide, a preparation way is provided for application of the nano oxide in the fields of energy, environment, sensing and the like, and the prepared modified ruthenium-based acidic oxygen evolution catalyst is small and uniform in particle, clean in surface, free of ligands and suitable for industrial production. The catalyst shows high activity and high stability on oxygen evolution reaction, and a new choice is provided for a commercial anode catalyst for producing hydrogen by electrolyzing water.

Description

Technical Field

[0001] The invention relates to the field of nanomaterials and catalytic technology, and in particular to a modified ruthenium-based acidic oxygen evolution catalyst and a preparation method and application thereof. Background Art

[0002] As a typical clean fuel, hydrogen has an energy density (140MJ / kg) much higher than traditional solid fuels (50MJ / kg), and is widely available and has zero carbon emissions during use. Therefore, it is considered an ideal carrier for future energy storage and supply. Among the many hydrogen production methods, proton exchange membrane (PEM) water electrolysis not only has a higher working current density (>1A / cm 2 ), lower ohmic loss, higher hydrogen purity (>99.99%), and faster dynamic response, these characteristics determine its stronger adaptability to fluctuating renewable energy power systems.

[0003] However, the oxygen evolution reaction at the anode of PEM water electrolysis involves multi-electron transfer and has a higher reaction barrier, which restricts the overall energy conversion efficiency of water electrolysis; in addition, the local acidic environment and high anode potential formed by the anode catalyst layer of PEM water electrolysis during the electrolysis process will severely test the stability of the oxygen evolution catalyst and thus affect the life of the membrane electrode. Ir-based catalysts are the mainstream PEM water electrolysis anode catalysts on the current market, but problems such as scarce Ir metal reserves, high prices, and poor activity limit their application in large-scale PEM water electrolysis scenarios. Compared with Ir-based catalysts, Ru has relatively considerable reserves and prices, and high oxygen evolution activity, but its stability needs to be further improved. Therefore, the modification of ruthenium oxide to prepare ruthenium-based catalysts with both high activity and high stability will help promote the commercialization of PEM water electrolysis. Summary of the invention

[0004] In order to solve the above technical problems, the purpose of the present invention is to provide a modified ruthenium-based acidic oxygen evolution catalyst and its preparation method and application, so as to solve the problems of scarce Ir metal reserves, high prices and poor activity of Ir-based catalysts in existing PEM water electrolysis anode catalysts, and low catalytic stability of Ru-based catalysts.

[0005] The technical solution of the present invention to solve the above technical problems is as follows:

[0006] A method for preparing a modified ruthenium-based acidic oxygen evolution catalyst comprises the following steps:

[0007] Firstly, a transition metal salt and a soluble ruthenium salt mixed solution is mixed with a complex ligand dispersion, then evaporated and solidified to obtain a metal chelate precursor, and finally pyrolyzed and oxidized to obtain;

[0008] The transition metal salt includes at least one of soluble Nb, Ti, Cr, Mn, Co, Cd, Sn and Sb metal salts.

[0009] The beneficial effects of the present invention are as follows: the present invention prepares the modified ruthenium-based acidic oxygen evolution catalyst by means of improved sol-gel and low-temperature calcination, the preparation method is simple, the synthesis efficiency is high, the effect is stable, and it is suitable for scaled-up production.

[0010] Further, soluble ruthenium salts include RuCl3, Ru(acac)3, Ru(CH3COO)3 and Ru(NO)(NO3) x (OH) y Any one of .

[0011] Further, the soluble Nb, Ti, Cr, Mn, Co, Cd, Sn and Sb metal salts include chlorides, acetates, organic acid salts, nitro salts or alkoxides.

[0012] Furthermore, the solvent of the mixed solution of transition metal salt and soluble ruthenium salt includes at least one of water, methanol, ethanol, isopropanol and ethylene glycol.

[0013] Furthermore, the complexing ligand includes at least one of ethylene glycol bis(2-aminoethyl ether) tetraacetic acid, propylene oxide, ethylenediaminetetraacetic acid, polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer, polyacrylic acid and polyoxyethylene polyoxypropylene ether triblock copolymer; the solvent of the complexing ligand dispersion includes at least one of water, methanol, ethanol, isopropanol and ethylene glycol, and the pH is adjusted to 9-13 with an alkaline substance; the alkaline substance includes ammonia water or ethylenediamine.

[0014] Furthermore, the molar ratio of the transition metal to ruthenium is x:1-x, wherein 0<x<1.

[0015] Furthermore, the evaporation solidification method includes any one of heating and stirring evaporation, vacuum heating evaporation and freeze drying.

[0016] Preferably, the evaporative solidification method is freeze drying.

[0017] Furthermore, the conditions for pyrolysis and oxidation are: in air or pure oxygen atmosphere, heating to 300-600° C. at a heating rate of 1-10° C. / min and keeping the temperature for 2-5 hours.

[0018] Preferably, the conditions for pyrolysis and oxidation are: in an air atmosphere, heating to 450° C. at a heating rate of 5° C. / min and keeping the temperature for 3 h.

[0019] A modified ruthenium-based acidic oxygen evolution catalyst is prepared by adopting the preparation method.

[0020] The beneficial effects of the present invention are as follows: the modified ruthenium-based acidic oxygen evolution catalyst prepared by the present invention has a small and uniform size, exhibits excellent catalytic activity and stability in the acidic oxygen evolution reaction, and exhibits a high catalytic activity and stability in a 0.5 mol / L sulfuric acid solution at 10 mA / cm 2 At the current density, the overpotential is only 268 mV, which is 89 mV lower than that of commercial ruthenium oxide, and exhibits better stability than commercial ruthenium oxide catalysts.

[0021] Furthermore, the modified ruthenium-based acidic oxygen evolution catalyst is a nano-oxide particle, and the chemical formula of the oxide is A x Ru 1-x O 2-y , A is any one of the transition metals Nb, Ti, Cr, Mn, Co, Cd, Sn and Sb, wherein x is the molar fraction and 0<x<1, 0<y<2.

[0022] Furthermore, the size of the nano-oxide particles is 5-15 nm.

[0023] Application of the modified ruthenium-based acidic oxygen evolution catalyst in the preparation of proton exchange membrane water electrolysis devices.

[0024] The present invention has the following beneficial effects:

[0025] The present invention adopts the sol-gel method and low-temperature calcination to prepare the modified ruthenium-based acidic oxygen evolution catalyst. The preparation process is simple and easy, the precursor salt selection is flexible, and the synthesis method is highly scalable in preparing nano-oxides, which provides a preparation method for nano-oxides used in energy, environment, sensing and other fields. The prepared modified ruthenium-based acidic oxygen evolution catalyst has small and uniform particles, a clean surface without ligands, and exhibits high activity and high stability for oxygen evolution reaction, which provides a new choice for commercial anode catalysts for hydrogen production by water electrolysis. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 Prepare Nb-RuO for Example 1 2-x XRD structural characterization and morphology of nanocatalysts;

[0027] Figure 2 Prepare Nb-RuO for Example 1 2-x X-ray photoelectron spectrum of nanocatalyst;

[0028] Figure 3 Prepare Nb-RuO for Example 1 2-x The electrochemical polarization curve and AC impedance spectrum of the acidic oxygen evolution reaction of the nanocatalyst were tested by linear voltammetry and AC impedance method in a three-electrode system.

[0029] Figure 4 For Example 2, Nb0.1 -Ru 0.9 O 2-x Voltage-time curve of nanocatalyst;

[0030] Figure 5 For Example 2, Nb 0.1 -Ru 0.9 O 2-x Membrane electrode current-voltage curve of nanocatalyst. DETAILED DESCRIPTION

[0031] The principles and features of the present invention are described below in conjunction with the accompanying drawings. The examples are only used to explain the present invention and are not used to limit the scope of the present invention. If specific conditions are not specified in the embodiments, they are carried out according to normal conditions or conditions recommended by the manufacturer. If the manufacturer is not specified for the reagents or instruments used, they are all conventional products that can be purchased commercially.

[0032] Embodiment 1:

[0033] A method for preparing a modified ruthenium-based acidic oxygen evolution catalyst comprises the following steps:

[0034] (1) preparing a niobium-ruthenium mixed salt solution: according to a molar ratio of Nb:Ru of 2:8, 27 mg of niobium pentachloride and 83.1 mg of ruthenium trichloride were weighed and dissolved in 6 mL of anhydrous ethanol, and ultrasonically dispersed in an ice-water bath to obtain a solution I, which was stored in an ice-water bath for later use;

[0035] (2) preparing a complex ligand dispersion: weighing 200 mg of the polyoxyethylene polyoxypropylene ether triblock copolymer, dissolving it in 10 mL of deionized water to obtain a dispersion II;

[0036] (3) placing the dispersion II on a magnetic stirrer for stirring, then injecting the solution I into the dispersion II, and continuing stirring for 6 h, then freezing the resulting dark brown colloid with liquid nitrogen, and placing it in a freeze dryer for freeze drying to obtain a metal chelate precursor;

[0037] (4) Under air atmosphere, the metal chelate precursor material obtained in step (3) is placed in a box furnace, and the temperature is raised to 450° C. at a rate of 5° C. / min, and calcined for 3 h. After the calcination, the mixture is naturally cooled to room temperature to obtain a modified ruthenium-based acidic oxygen evolution catalyst Nb-RuO 2-x (0<x<2).

[0038] Embodiment 2:

[0039] A method for preparing a modified ruthenium-based acidic oxygen evolution catalyst comprises the following steps:

[0040] (1) preparing a niobium-ruthenium mixed salt solution: according to a molar ratio of Nb:Ru of 1:9, 13.5 mg of niobium pentachloride and 93.5 mg of ruthenium trichloride were weighed and dissolved in 6 mL of anhydrous ethanol, and ultrasonically dispersed in an ice-water bath to obtain a solution I, which was stored in an ice-water bath for later use;

[0041] (2) preparing a complex ligand dispersion: weighing 200 mg of the polyoxyethylene polyoxypropylene ether triblock copolymer, dissolving it in 10 mL of deionized water to obtain a dispersion II;

[0042] (3) placing the dispersion II on a magnetic stirrer for stirring, then injecting the solution I into the dispersion II, and continuing stirring for 6 h, then freezing the resulting dark brown colloid with liquid nitrogen, and placing it in a freeze dryer for freeze drying to obtain a metal chelate precursor;

[0043] (4) In an air atmosphere, the metal chelate precursor material obtained in step (3) is placed in a box furnace, the temperature is raised to 450° C. at a rate of 5° C. / min, and calcined for 3 h. After the calcination, the mixture is naturally cooled to room temperature to obtain a modified ruthenium-based acidic oxygen evolution catalyst Nb 0.1 -Ru 0.9 O 2-x (0<x<2).

[0044] Embodiment 3:

[0045] A method for preparing a modified ruthenium-based acidic oxygen evolution catalyst comprises the following steps:

[0046] (1) preparing a manganese-ruthenium mixed salt solution: according to a molar ratio of Mn:Ru of 2:8, 16.2 mg of manganese chloride and 83.1 mg of ruthenium trichloride were weighed and dissolved in 6 mL of anhydrous ethanol, and ultrasonically dispersed in an ice-water bath to obtain a solution I, which was stored in an ice-water bath for later use;

[0047] (2) preparing a complex ligand dispersion: weighing 200 mg of the polyoxyethylene polyoxypropylene ether triblock copolymer, dissolving it in 10 mL of deionized water to obtain a dispersion II;

[0048] (3) placing the dispersion II on a magnetic stirrer for stirring, then injecting the solution I into the dispersion II, and continuing stirring for 6 h, then freezing the resulting dark brown colloid with liquid nitrogen, and placing it in a freeze dryer for freeze drying to obtain a metal chelate precursor;

[0049] (4) Under air atmosphere, the metal chelate precursor material obtained in step (3) is placed in a box furnace, and the temperature is raised to 450° C. at a rate of 5° C. / min, and calcined for 3 h. After calcination, the mixture is naturally cooled to room temperature to obtain a modified ruthenium-based acidic oxygen evolution catalyst Mn-RuO 2-x (0<x<2).

[0050] Embodiment 4:

[0051] A method for preparing a modified ruthenium-based acidic oxygen evolution catalyst comprises the following steps:

[0052] (1) preparing a niobium-ruthenium mixed salt solution: according to a molar ratio of Ti:Ru of 2:8, 19.10 mg of titanium tetrachloride and 83.1 mg of ruthenium trichloride were weighed and dissolved in 6 mL of anhydrous ethanol, and ultrasonically dispersed in an ice-water bath to obtain a solution I, which was stored in an ice-water bath for later use;

[0053] (2) preparing a complex ligand dispersion: weighing 200 mg of the polyoxyethylene polyoxypropylene ether triblock copolymer, dissolving it in 10 mL of deionized water to obtain a dispersion II;

[0054] (3) placing the dispersion II on a magnetic stirrer for stirring, then injecting the solution I into the dispersion II, and continuing stirring for 6 h, then freezing the resulting dark brown colloid with liquid nitrogen, and placing it in a freeze dryer for freeze drying to obtain a metal chelate precursor;

[0055] (4) Under air atmosphere, the metal chelate precursor material obtained in step (3) is placed in a box furnace, and the temperature is raised to 450° C. at a rate of 5° C. / min, and calcined for 3 h. After the calcination, the mixture is naturally cooled to room temperature to obtain a modified ruthenium-based acidic oxygen evolution catalyst Ti-RuO 2-x (0<x<2).

[0056] Test example:

[0057] The modified ruthenium-based acidic oxygen evolution catalyst Nb-RuO prepared in Example 1 2-x X-ray diffraction analysis, surface morphology analysis and X-ray photoelectron spectroscopy analysis were performed. The experimental results are as follows Figure 1 and Figure 2 As shown, Figure 1 It shows that the modified ruthenium-based acidic oxygen evolution catalyst Nb-RuO prepared by the present invention 2-x The particles are small and uniform, with a clean surface and no ligands, and a size of 5-10nm. Figure 2 The elemental composition of the catalyst is shown.

[0058] The modified ruthenium-based acidic oxygen evolution catalyst Nb-RuO prepared in Example 1 2-x For oxygen evolution reaction in acidic environment, commercial RuO2 catalyst was used as comparison. A three-electrode test system was used, with platinum wire as counter electrode and mercury / mercury sulfate electrode as reference electrode: 5 mg Nb-RuO 2-x The nanocatalyst was dispersed into a uniform catalyst slurry in 1 mL of a mixed solvent of water and isopropanol. A certain amount was evenly dropped onto a glassy carbon electrode with a diameter of 5 mm as a working electrode. The loading was 0.25 mg / cm 2, in preparation for testing. The test system selected 0.5 mol / L sulfuric acid solution as the electrolyte, continuously introduced oxygen to maintain oxygen saturation, and used linear voltammetry scanning and AC impedance method to test electrochemical data. The linear voltammetry scanning rate was 5 mV / s, and the test potential of AC impedance was 1.5 V (vs. RHE).

[0059] The experimental results are as follows Figure 3 The results show that at 10mA / cm 2 At a current density of 2-x The overpotential of the nanocatalyst is 268 mV, and the overpotential of the commercial RuO2 catalyst is 357 mV; Figure 3 As shown in Figure b, Nb-RuO 2-x The charge transfer resistance of the nanocatalyst is smaller than that of the commercial RuO2 catalyst, indicating that Nb-RuO 2-x The nanocatalyst has a faster electron transfer rate, reflecting its higher oxygen evolution catalytic activity.

[0060] The modified ruthenium-based acidic oxygen evolution catalyst Nb 0.1 -Ru 0.9 O 2-x The stability and activity were measured using an industrial standard membrane electrode test system, and the catalyst applied voltage-time curve and membrane electrode current-voltage curve were measured respectively.

[0061] The experimental results are as follows Figure 4 As shown, the results show that the modified ruthenium-based acidic oxygen evolution catalyst Nb 0.1 -Ru 0.9 O 2-x Possess high stability; Figure 5 As shown, the modified ruthenium-based acidic oxygen evolution catalyst Nb prepared by the present invention 0.1 -Ru 0.9 O 2-x Highly active, 2Acm at 1.8V operating voltage -2 The working current.

[0062] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a modified ruthenium-based acidic oxygen evolution catalyst, characterized in that: The following steps are involved: Firstly, a transition metal salt and a soluble ruthenium salt mixed solution is mixed with a complex ligand dispersion, then evaporated and solidified to obtain a metal chelate precursor, and finally pyrolyzed and oxidized to obtain; The transition metal salt includes at least one of soluble Nb, Ti, Cr, Mn, Co, Cd, Sn and Sb metal salts.

2. The method for preparing the modified ruthenium-based acidic oxygen evolution catalyst according to claim 1, characterized in that: The soluble ruthenium salts include RuCl3, Ru(acac)3, Ru(CH3COO)3 and Ru(NO)(NO3) x (OH) y Any one of .

3. The method for preparing the modified ruthenium-based acidic oxygen evolution catalyst according to claim 1, characterized in that: Soluble metal salts of Nb, Ti, Cr, Mn, Co, Cd, Sn and Sb include chlorides, acetates, organic acid salts, nitro salts or alcohol salts.

4. The method for preparing the modified ruthenium-based acidic oxygen evolution catalyst according to claim 1, characterized in that: The solvent of the mixed solution of transition metal salt and soluble ruthenium salt includes at least one of water, methanol, ethanol, isopropanol and ethylene glycol.

5. The method for preparing the modified ruthenium-based acidic oxygen evolution catalyst according to claim 1, characterized in that: The complexing ligand comprises at least one of ethylene glycol bis(2-aminoethyl ether) tetraacetic acid, propylene oxide, ethylenediaminetetraacetic acid, polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer, polyacrylic acid and polyoxyethylene polyoxypropylene ether triblock copolymer; the solvent of the complexing ligand dispersion comprises at least one of water, methanol, ethanol, isopropanol and ethylene glycol, and the pH is adjusted to 9-13 with an alkaline substance; the alkaline substance comprises ammonia water or ethylenediamine.

6. The method for preparing the modified ruthenium-based acidic oxygen evolution catalyst according to claim 1, characterized in that: The molar ratio of the transition metal to ruthenium is x:1-x, wherein 0<x<1.

7. The method for preparing the modified ruthenium-based acidic oxygen evolution catalyst according to claim 1, characterized in that: The evaporation solidification method includes any one of heating and stirring evaporation, vacuum heating evaporation and freeze drying.

8. The method for preparing the modified ruthenium-based acidic oxygen evolution catalyst according to claim 1, characterized in that: The conditions for the pyrolysis oxidation are: in air or pure oxygen atmosphere, heating to 300-600° C. at a heating rate of 1-10° C. / min and keeping the temperature for 2-5 hours.

9. A modified ruthenium-based acidic oxygen evolution catalyst, characterized in that: The method is prepared by the method according to any one of claims 1 to 8.

10. Use of the modified ruthenium-based acidic oxygen evolution catalyst according to claim 9 in the preparation of a proton exchange membrane water electrolysis device.

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