Modified nano ruthenium oxide catalyst as well as preparation method and application thereof

Abstract

The invention discloses a modified nano ruthenium oxide 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: mixing a low-melting-point inorganic salt solution with a mixed solution of a transition metal salt and a soluble ruthenium salt, and carrying out evaporative crystallization to obtain a mixed salt crystal; roasting the mixed salt crystal, and then cleaning and drying to obtain the catalyst. Wherein the transition metal salt comprises any one of soluble salts of Na, Sr, Ba, Sc, Y and Zr. A low-temperature molten salt method is adopted, the preparation process is simple and easy to implement, raw materials are flexible to select, the synthesis method has high expansibility in preparation of the nano oxide, and a preparation approach is provided for application of the nano oxide in the fields of energy, environment, sensing and the like; high activity and high stability are shown on oxygen evolution reaction, and a new choice is provided for a commercial anode catalyst for PEM water electrolysis hydrogen production.

Description

Technical Field

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

[0002] Efficient and sustainable production of hydrogen is the primary link in achieving the promotion and application of hydrogen energy. Hydrogen production by water electrolysis driven by renewable energy such as solar energy and wind energy is the most ideal sustainable hydrogen production solution. Compared with traditional alkaline water electrolysis, proton exchange membrane (PEM) water electrolysis has the advantages of fast start-stop response, wide threshold load current, and no need to purify hydrogen products. It is more compatible with the aforementioned renewable energy sources with fluctuating characteristics such as solar energy.

[0003] However, the oxygen evolution reaction at the anode of PEM water electrolysis involves multiple electron transfers and exhibits a high reaction barrier. Combined with the local acidic environment formed on the proton exchange membrane during the electrolysis process and the high potential of the anode, higher requirements are placed on the activity and stability of the oxygen evolution catalyst. It is urgent to develop acidic oxygen evolution catalysts with both high activity and stability to promote the development of PEM electrolysis technology. Related research focuses on Ir, Ru and their metal oxides, but the scarce reserves, high price and poor activity of Ir limit its large-scale application in PEM water electrolysis. 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 is of great significance to 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 nano ruthenium oxide 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 nano-ruthenium oxide catalyst comprises the following steps:

[0007] (1) mixing a low melting point inorganic salt solution with a mixed solution of a transition metal salt and a soluble ruthenium salt, evaporating and crystallizing to obtain mixed salt crystals;

[0008] (2) calcining the mixed salt crystals obtained in step (1), and then washing and drying them to obtain;

[0009] Wherein, the transition metal salt includes any one of soluble salts of Na, Sr, Ba, Sc, Y and Zr.

[0010] The beneficial effects of the present invention are as follows: the preparation process of the present invention is simple and easy, the raw material selection is flexible, the preparation is carried out by a low-temperature molten salt method, it has a high degree of scalability in the preparation of nano oxides, the preparation conditions are mild, and it is more suitable for large-scale production.

[0011] Furthermore, in step (1), the low melting point inorganic salt includes at least one of KCl, KSCN, KNO3 and KNO2; the concentration of the low melting point inorganic salt solution is 10-100 g / L; and the volume ratio of the low melting point inorganic salt solution to the mixed solution of the transition metal salt and the soluble ruthenium salt is 5-15:3-7.

[0012] Furthermore, the soluble ruthenium salt in step (1) includes RuCl3, Ru(acac)3, Ru(CH3COO)3 and Ru(NO)(NO3) x (OH) y Any one of .

[0013] Further, the soluble salt of Na, Sr, Ba, Sc, Y and Zr includes any one of chlorides, acetates, nitrates and alkoxides of Na, Sr, Ba, Sc, Y and Zr.

[0014] Furthermore, in step (1), the molar ratio of ruthenium to transition metal in the mixed solution of transition metal salt and soluble ruthenium salt is 1-x:x, 0<x<1; and the total concentration of the mixed solution of transition metal salt and soluble ruthenium salt is 10-20 g / L.

[0015] Furthermore, the evaporative crystallization method in step (1) is any one of heating and stirring evaporation, vacuum heating evaporation and freeze drying.

[0016] Furthermore, the calcination treatment conditions in step (2) are: heating to 300-600°C at a heating rate of 1-10°C / min and keeping the temperature for 2-5h.

[0017] Preferably, the calcination treatment conditions in step (2) are: heating to 400° C. at a heating rate of 5° C. / min and keeping the temperature for 2-5 h.

[0018] A modified nanometer ruthenium oxide catalyst is prepared by adopting the preparation method.

[0019] The beneficial effects of the present invention are as follows: the modified nano-ruthenium oxide catalyst material prepared by the present invention is used for oxygen evolution reaction under acidic conditions, and exhibits excellent catalytic activity and stability. 2 At the current density, the overpotential is only 261 mV, which is 96 mV lower than that of commercial ruthenium oxide, and exhibits better stability than commercial ruthenium oxide catalysts.

[0020] The modified nano-ruthenium oxide catalyst is used in the preparation of a proton exchange membrane water electrolysis device.

[0021] The present invention has the following beneficial effects:

[0022] (1) The present invention adopts a low-temperature molten salt method to prepare modified ruthenium oxide nanoparticles. The prepared nanoparticles are small and uniform, and the surface is clean and free of ligands.

[0023] (2) The preparation process of the present invention is simple and easy, the raw material selection is flexible, and the synthesis method is highly scalable in the preparation of nano-oxides, providing a preparation method for nano-oxides used in energy, environment, sensing and other fields.

[0024] (3) Na-RuO prepared by the present invention 2-x The nanocatalysts exhibit high activity and stability for the oxygen evolution reaction, providing a new choice for commercial anode catalysts for hydrogen production by PEM water electrolysis. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 The Na-RuO prepared in Example 1 2-x Structural characterization and morphology of nanocatalysts;

[0026] Figure 2 The Na-RuO prepared in 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.

[0027] Figure 3 The Na-RuO prepared in Example 1 2-x Nanocatalyst at 10mA / cm 2 Stability test diagram under current density. DETAILED DESCRIPTION

[0028] 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.

[0029] Embodiment 1:

[0030] A method for preparing a modified nano-ruthenium oxide catalyst comprises the following steps:

[0031] (1) Preparation of KNO3 salt solution: weigh 500 mg of KNO3 and dissolve it in 10 mL of deionized water to obtain solution A;

[0032] (2) preparing a mixed solution of ruthenium trichloride and sodium chloride: weighing 75 mg of RuCl3 and 4 mg of NaCl, respectively, and dissolving them in 5 mL of deionized water at a molar ratio of Na:Ru of 1:9 to obtain solution B;

[0033] (3) mixing solution A obtained in step (1) and solution B obtained in step (2), stirring for 30 min, freezing, and placing in a freeze dryer for freeze drying for 30 h to obtain mixed salt crystals;

[0034] (4) placing the mixed salt crystals obtained in step (4) in a box furnace under air atmosphere, heating the temperature to 400° C., and calcining for 3 h;

[0035] (5) The product after calcination in step (4) was washed with deionized water to remove residual inorganic salts, and the washing was repeated 5 times. Finally, the product was placed in a vacuum drying oven for drying to obtain a modified nano-ruthenium oxide catalyst Na-RuO 2-x .

[0036] Embodiment 2:

[0037] A method for preparing a modified nano-ruthenium oxide catalyst comprises the following steps:

[0038] (1) Prepare KNO3 salt solution: weigh 500 mg KNO2 and dissolve it in 10 mL deionized water to obtain solution A;

[0039] (2) preparing a mixed solution of ruthenium trichloride and sodium chloride: weighing 75 mg of RuCl3 and 14.22 mg of BaCl2, respectively, in a molar ratio of Na:Ru of 1:9 and dissolving them in 5 mL of deionized water to obtain solution B;

[0040] (3) mixing solution A obtained in step (1) and solution B obtained in step (2), stirring for 30 min, freezing, and placing in a freeze dryer for freeze drying for 30 h to obtain mixed salt crystals;

[0041] (4) placing the mixed salt crystals obtained in step (4) in a box furnace under air atmosphere, heating the temperature to 400° C., and calcining for 3 h;

[0042] (5) The calcined product of step (4) was washed with deionized water to remove residual inorganic salts, and the washing was repeated 5 times. Finally, the product was placed in a vacuum drying oven for drying to obtain a modified nano-ruthenium oxide catalyst.

[0043] Embodiment 3:

[0044] A method for preparing a modified nano-ruthenium oxide catalyst comprises the following steps:

[0045] (1) Prepare KNO3 salt solution: weigh 500 mg KCl and dissolve it in 10 mL deionized water to obtain solution A;

[0046] (2) preparing a mixed solution of ruthenium trichloride and sodium chloride: weighing 75 mg of RuCl3 and 10.84 mg of SrCl2, respectively, in a molar ratio of Na:Ru of 1:9 and dissolving them in 5 mL of deionized water to obtain solution B;

[0047] (3) mixing solution A obtained in step (1) and solution B obtained in step (2), stirring for 30 min, freezing, and placing in a freeze dryer for freeze drying for 30 h to obtain mixed salt crystals;

[0048] (4) placing the mixed salt crystals obtained in step (4) in a box furnace under air atmosphere, heating the temperature to 400° C., and calcining for 3 h;

[0049] (5) The calcined product of step (4) was washed with deionized water to remove residual inorganic salts, and the washing was repeated 5 times. Finally, the product was placed in a vacuum drying oven for drying to obtain a modified nano-ruthenium oxide catalyst.

[0050] Embodiment 4:

[0051] A method for preparing a modified nano-ruthenium oxide catalyst comprises the following steps:

[0052] (1) Preparation of KNO3 salt solution: weigh 500 mg of KSCN and dissolve it in 10 mL of deionized water to obtain solution A;

[0053] (2) preparing a mixed solution of ruthenium trichloride and sodium chloride: weighing 66.67 mg of RuCl3 and 8 mg of NaCl, respectively, and dissolving them in 5 mL of deionized water at a molar ratio of Na:Ru of 2:8 to obtain solution B;

[0054] (3) mixing solution A obtained in step (1) and solution B obtained in step (2), stirring for 30 min, freezing, and placing in a freeze dryer for freeze drying for 30 h to obtain mixed salt crystals;

[0055] (4) placing the mixed salt crystals obtained in step (4) in a box furnace under air atmosphere, heating the temperature to 400° C., and calcining for 3 h;

[0056] (5) The calcined product of step (4) was washed with deionized water to remove residual inorganic salts, and the washing was repeated 5 times. Finally, the product was placed in a vacuum drying oven for drying to obtain a modified nano-ruthenium oxide catalyst.

[0057] Test example:

[0058] Take the Na-RuO prepared in Example 1 2-xThe nanocatalyst was subjected to X-ray diffraction experiments and surface SEM morphology determination.

[0059] The experimental results are as follows Figure 1 As shown, it shows that Na-RuO 2-x The successful synthesis of the nanocatalyst and the synthesized Na-RuO 2-x Nanocatalyst nanoparticles are small and uniform in size, ranging from 5-20nm, with a clean surface and no ligands.

[0060] Take the Na-RuO prepared in Example 2-x The nanocatalyst was used for oxygen evolution reaction in an acidic environment. A three-electrode test system was used, with platinum wire as the counter electrode and mercury / mercurous sulfate electrode as the reference electrode. 5 mg Na-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 an electrode diameter of 5 mm as a working electrode. The loading was 0.25 mg / cm 2 , in preparation for testing. The test system selected 0.5mol / L sulfuric acid solution as the electrolyte, continuously introduced oxygen to maintain oxygen saturation, and used linear voltammetry and AC impedance method to test electrochemical data. The linear voltammetry scan rate was 5mV / s, and the AC impedance test potential was 1.5V (vs.RHE). And at 10mA / cm 2 Under current density, Na-RuO 2-x Stability of nanocatalysts.

[0061] The experimental results are as follows Figure 2 and Figure 3 As shown, the results show that at 10mA / cm 2 At a current density of 2-x The overpotential of the nanocatalyst is 261 mV, and the overpotential of the commercial RuO2 catalyst is 357 mV; Figure 2 As shown in Figure b, Na-RuO 2-x The charge transfer resistance of the nanocatalyst is smaller than that of the commercial RuO2 catalyst, indicating that Na-RuO 2-x Nanocatalysts have smaller charge transfer resistance, reflecting their higher oxygen evolution catalytic activity; e.g. Figure 3 As shown in the figure, the potential increased by only 85 mV after 30 h of continuous operation, indicating that Na-RuO 2-x Among nanocatalysts, it has high stability.

[0062] In summary, the modified nano-ruthenium oxide catalyst prepared by the present invention has both high activity and high stability, providing a new reference for breaking through the technical bottleneck of proton exchange membrane water electrolysis.

[0063] 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 nano-ruthenium oxide catalyst, characterized in that: The following steps are involved: (1) mixing a low melting point inorganic salt solution with a mixed solution of a transition metal salt and a soluble ruthenium salt, evaporating and crystallizing to obtain mixed salt crystals; (2) calcining the mixed salt crystals obtained in step (1), and then washing and drying them to obtain; Wherein, the transition metal salt includes any one of soluble salts of Na, Sr, Ba, Sc, Y and Zr.

2. The method for preparing the modified nano-ruthenium oxide catalyst according to claim 1, characterized in that: In the step (1), the low melting point inorganic salt comprises at least one of KCl, KSCN, KNO3 and KNO2; the concentration of the low melting point inorganic salt solution is 10-100 g / L; the volume ratio of the low melting point inorganic salt solution to the mixed solution of the transition metal salt and the soluble ruthenium salt is 5-15:3-7.

3. The method for preparing the modified nano-ruthenium oxide catalyst according to claim 1, characterized in that: The soluble ruthenium salt in step (1) includes RuCl3, Ru(acac)3, Ru(CH3COO)3 and Ru(NO)(NO3) x (OH) y Any one of .

4. The method for preparing the modified nano-ruthenium oxide catalyst according to claim 1, characterized in that: The soluble salts of Na, Sr, Ba, Sc, Y and Zr include any one of chlorides, acetates, nitrates and alkoxides of Na, Sr, Ba, Sc, Y and Zr.

5. The method for preparing the modified nano-ruthenium oxide catalyst according to claim 1, characterized in that: In the step (1), the molar ratio of ruthenium to transition metal in the mixed solution of transition metal salt and soluble ruthenium salt is 1-x:x, 0<x<1; and the total concentration of the mixed solution of transition metal salt and soluble ruthenium salt is 10-20 g / L.

6. The method for preparing the modified nano-ruthenium oxide catalyst according to claim 1, characterized in that: The evaporative crystallization method in step (1) is any one of heating and stirring evaporation, vacuum heating evaporation and freeze drying.

7. The method for preparing the modified nano-ruthenium oxide catalyst according to claim 1, characterized in that: The conditions for the calcination treatment in step (2) are: heating to 300-600° C. at a heating rate of 1-10° C. / min and keeping the temperature for 2-5 hours.

8. A modified nano-ruthenium oxide catalyst, characterized in that: The method is prepared by the preparation method according to any one of claims 1 to 7.

9. Use of the modified nano-ruthenium oxide catalyst according to claim 8 in the preparation of a proton exchange membrane water electrolysis device.

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