Porous ruthenium-based oxide, preparation method and application

Abstract

The invention discloses a porous ruthenium-based oxide as well as a preparation method and application thereof. Rich ruthenium metal site types and proportion regulation and control ranges are provided, the utilization efficiency of precious metal components is improved, and excellent oxygen evolution reaction catalytic activity is provided for the catalyst; transition metal or rare earth metal is doped to provide a more stable acid-resistant and high-potential structural framework for the catalyst, so that the working stability of the catalyst in an oxidation environment is improved; the loose porous catalyst structure is beneficial to rapid mass transfer of gas, structural damage caused by gassing is reduced, excessive oxidation dissolution of ruthenium is avoided, and the structural stability of the catalyst is improved. The porous ruthenium-based oxide OER catalyst with high catalytic activity and a stable structure can be prepared by the method, and is suitable for application scenes of an anode reaction catalyst in a proton membrane electrolytic cell and other oxygen evolution reaction catalysis.

Description

Technical Field

[0001] The present invention relates to the technical field of novel material preparation, and in particular to a porous ruthenium-based oxide, a preparation method and application thereof. Background Art

[0002] With the increasing global energy demand, the urgent need to mitigate climate change has accelerated the development of sustainable and clean energy technologies as alternatives to fossil fuels. Hydrogen is one of the renewable zero-carbon energy sources among fossil fuels and has been considered the most promising clean fuel. Hydrogen synthesis by water electrolysis (WE) has become a promising strategy to produce clean energy carriers from water and low-carbon electricity, providing a way to decarbonize global industry. Among different WE technologies, acidic water electrolysis technology using proton exchange membrane (PEM) water electrolyzer has the advantages of fast system response, high current density and voltage efficiency, and high gas purity. However, most catalysts have poor stability in strongly acidic, high-voltage oxidative electrochemical environments, and iridium-based precious metal materials are almost exclusively used as acidic oxygen evolution reaction (OER) catalysts in commercial products. Although iridium-based catalysts have excellent OER activity, the cost and supply of iridium are key factors restricting PEM water electrolysis in the future. In order to reduce the amount of iridium and reduce the cost of anode catalysts, it is urgent to further develop non-iridium-based OER catalysts to meet the application of anode catalysts in PEM water electrolyzers. Summary of the invention

[0003] The present invention aims to solve one of the technical problems in the related art at least to a certain extent.

[0004] To this end, the embodiments of the present invention provide a porous ruthenium-based oxide and a preparation method and application thereof. The present invention provides a porous ruthenium-based oxide with high catalytic activity and stability doped with transition metals or rare earth metals through precursor ultrasonic mixing method coupled with high temperature calcination method and etching method, which is used in electrolytic cell anode and other oxygen evolution reaction catalyst application scenarios.

[0005] In a first aspect, the present invention provides a method for preparing a porous ruthenium-based oxide, comprising the following steps:

[0006] (a) adding a ruthenium salt, a metal M precursor salt and a zinc salt in a molar ratio of 1:(0.2-2):(1-2) to a solvent, ultrasonically mixing to prepare a precursor solution, and drying to obtain a precursor mixture, wherein the metal M is a transition metal or a rare earth metal;

[0007] (b) calcining the precursor mixture to obtain a ruthenium-based oxide, denoted as RuMZnO x ;

[0008] (c) etching the ruthenium-based oxide powder in a sulfuric acid solution with a molar ratio of 0.5 to 3, centrifugally washing and drying to obtain a porous ruthenium-based oxide, denoted as p-RuMO x .

[0009] Wherein, in step (a), the ruthenium salt is ruthenium chloride or ruthenium acetate, or other soluble ruthenium salts; the zinc salt is zinc nitrate or zinc chloride, or other soluble zinc salts; the solvent is anhydrous ethanol, or other suitable solvents; the power of ultrasound can be selected according to the specific situation. The precursor solution is dried in an oven to obtain a uniform, viscous, blocky precursor mixture. Too little zinc salt addition results in low porosity of the final porous catalyst, and too much zinc salt prevents ruthenium from being firmly bonded to the oxide framework formed by the metal M, resulting in reduced catalytic performance.

[0010] In step (c), the ruthenium-based oxide is etched with a sulfuric acid solution to remove ZnO therein, thereby forming pores in the ruthenium-based oxide to make it porous. It is understandable that the ruthenium-based oxide is ground into powder before etching, thereby increasing the contact area between the ruthenium-based oxide and the sulfuric acid solution to make the etching faster and more uniform. Too much acid addition will lead to too fast etching, which may easily cause the catalyst structure to collapse; too little acid addition may lead to incomplete zinc etching and reduce the catalytic activity. In addition, p-RuMO x The value of x is related to the metal ratio.

[0011] In some embodiments, the transition metal includes at least one of gallium, indium, tin, bismuth, manganese, zinc, nickel, cobalt, molybdenum, copper, titanium, vanadium, chromium, niobium, tantalum, and tungsten.

[0012] In some embodiments, the rare earth metal includes at least one of lanthanum, cerium, erbium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, thulium, ytterbium, lutetium, scandium, and yttrium.

[0013] In some embodiments, the metal M precursor salt includes nitrate, chloride or acetate with a concentration of 0.1 to 500 mmol / L. It is understood that other suitable salts of metal M are also feasible.

[0014] In some embodiments, in step (a), the drying temperature is 60°C to 120°C, and the drying time is 1 to 6 hours. The drying temperature can be 60°C, 70°C, 80°C, 90°C, 100°C, 110°C, 120°C, or a value within a range consisting of any two values; the drying time is 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, or a value within a range consisting of any two values.

[0015] In some embodiments, the ultrasonic time in step (a) is 20 to 120 min. The ultrasonic time can be 20 min, 40 min, 60 min, 80 min, 100 min, 120 min, or a value within a range consisting of any two values.

[0016] In some embodiments, the calcination temperature in step (b) is 250°C to 850°C, and the calcination time is 1 to 5 hours. The calcination temperature can be 250°C, 350°C, 500°C, 600°C, 750°C, 850°C, or a value within a range consisting of any two values. The calcination time can be 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, or a value within a range consisting of any two values.

[0017] In some embodiments, in step (c), the etching temperature is 60°C to 90°C, and the etching time is 1 to 12 hours. The etching temperature can be 60°C, 70°C, 80°C, 90°C, or a value within a range consisting of any two values. The etching time is 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, or a value within a range consisting of any two values.

[0018] In some embodiments, the concentration of the sulfuric acid solution is 0.01-1 mol / L. The concentration of the sulfuric acid solution is 0.01 mol / L, 0.05 mol / L, 0.1 mol / L, 0.3 mol / L, 0.5 mol / L, 0.7 mol / L, 0.9 mol / L, 1 mol / L, or a value within a range consisting of any two values.

[0019] In a second aspect, the present invention provides a porous ruthenium-based oxide, which is prepared by the method proposed in the first aspect of the present invention, and has a pore size of 0.1 to 5 nm.

[0020] In a third aspect, the present invention provides the use of the porous ruthenium-based oxide prepared by the method provided in the first aspect or the porous ruthenium-based oxide provided in the second aspect in a proton membrane electrolyzer and a fuel cell anti-reverse electrode.

[0021] Compared with the prior art, the beneficial effects of the present invention are:

[0022] The present invention provides abundant types of ruthenium metal sites and a range of proportion control, thereby improving the utilization efficiency of the precious metal components and providing the catalyst with excellent catalytic activity for the oxygen evolution reaction; transition metal or rare earth metal doping provides the catalyst with a more stable acid-resistant and high-potential structural framework, thereby improving the working stability of the catalyst in an oxidizing environment; the loose and porous catalyst structure facilitates rapid gas mass transfer, reduces structural damage caused by gas evolution, avoids excessive oxidation and dissolution of ruthenium, and improves the structural stability of the catalyst.

[0023] The method of the present invention can prepare a porous ruthenium-based oxide OER catalyst with high catalytic activity and stable structure, which is suitable for use as an anode reaction catalyst in a proton membrane electrolyzer and other oxygen evolution reaction catalytic application scenarios. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The above and / or additional aspects and advantages of the present invention will become apparent and easily understood from the following description of the embodiments in conjunction with the accompanying drawings, in which:

[0025] Figure 1 This is the XRD image of the sample prepared in Example 1 of the present invention;

[0026] Figure 2 This is the XRD image of the sample prepared in Example 2 of the present invention;

[0027] Figure 3 This is the XRD image of the sample prepared in Example 3 of the present invention;

[0028] Figure 4 This is the XRD image of the sample prepared in Example 4 of the present invention;

[0029] Figure 5 XRD comparison diagram of samples prepared in Example 5 of the present invention and Comparative Example 1 (before and after acid etching);

[0030] Figure 6 This is a nitrogen adsorption-desorption curve diagram of the sample prepared in Example 1 of the present invention;

[0031] Figure 7 The IV curve of the sample prepared in Example 1 of the present invention in a PEM electrolyzer;

[0032] Figure 8 The oxygen evolution reaction activity curves of the samples prepared in Examples 1 to 5 of the present invention and Comparative Example 1 in a 0.5 mol / L sulfuric acid solution are shown. DETAILED DESCRIPTION

[0033] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, and should not be construed as limiting the present invention.

[0034] Example 1

[0035] 10 mmol RuCl3·nH2O, 3 mmol Ga(NO3)3·nH2O, and 16 mmol Zn(NO3)2·6H2O were added to 10 mL of anhydrous ethanol, ultrasonicated for 20 min, and mixed evenly to prepare a precursor solution.

[0036] Then, the precursor ethanol solution was dried in an oven at 80° C. for 2 h to obtain a viscous, blocky precursor mixture.

[0037] The precursor mixture was calcined in air at a heating rate of 5°C / min to 500°C and kept at this temperature for 2 h to obtain an oxide material, which was recorded as RuGaZnO. x .

[0038] Finally, the obtained RuGaZnO x Grind into powder, and mix the prepared RuGaZnO with 1g catalyst and 50mL sulfuric acid (0.5mol / L). x Acid etching was performed in a water bath at 80 °C for 2 h to remove ZnO, and the porous ruthenium-based oxide p-RuGaO was obtained by centrifugal washing until neutral and drying. x .

[0039] Example 2

[0040] 10 mmol RuCl3·nH2O, 3 mmol SnCl2, and 16 mmol Zn(NO3)2·6H2O were added to 10 mL of anhydrous ethanol, and ultrasonicated for 20 min to mix evenly to prepare a precursor solution. The other processes were the same as in Example 1 to obtain p-RuSnO x Powder material.

[0041] Example 3

[0042] 10 mmol RuCl3·nH2O, 3 mmol Er(NO3)3·5H2O, and 16 mmol Zn(NO3)2·6H2O were added to 10 mL of anhydrous ethanol, and ultrasonicated for 20 min to mix well to prepare a precursor solution. The other processes were the same as in Example 1 to obtain p-RuErO x Powder material.

[0043] Example 4

[0044] 10 mmol RuCl3·nH2O, 3 mmol La(NO3)3·6H2O, and 16 mmol Zn(NO3)2·6H2O were added to 10 mL of anhydrous ethanol, and ultrasonicated for 20 min to mix well to prepare a precursor solution. The other processes were the same as in Example 1 to obtain p-RuLaO x Powder material.

[0045] Example 5

[0046] 10 mmol RuCl3·nH2O, 3 mmol Mn(Ac)2·4H2O, and 16 mmol Zn(NO3)2·6H2O were added to 10 mL of anhydrous ethanol, and ultrasonicated for 20 min to mix evenly to prepare a precursor solution. The other processes were the same as in Example 1, and the product obtained was p-RuMnO x Powdered catalyst material.

[0047] Comparative Example 1

[0048] There is no sulfuric acid etching process, and the other processes are the same as in Example 5 to obtain RuMnZnO x Powder material.

[0049] The samples prepared in Examples 1 to 5 and Comparative Example 1 were subjected to X-ray crystal diffraction tests. The test results are as follows: Figure 1 to Figure 5 shown.

[0050] Depend on Figure 1 It can be seen that the circular marks of 28.0°, 35.1°, 40.0°, 40.5°, 54.2°, 57.9°, 59.4°, 65.5°, 67.0°, 69.5°, 74.1°, 83.4°, 86.4° and 87.7° correspond to the (110), (101), (200), (111), (211), (220), (002), (310), (112), (301), (202), (321), (400) and (222) crystal plane diffraction peaks of RuO2 (PDF#40-1290), respectively. No other phases were found, which indicates that the precursor is oxidized to ruthenium-based oxides after high-temperature calcination. The introduction of Ga element does not lead to the formation of new phases, but is only doped into the RuO2 crystal, causing a slight shift in the position of the RuO2 peak.

[0051] Depend on Figure 2 It can be seen that the diamond-shaped peaks 51.8°, 62.1° and 78.7° correspond to the (211), (310) and (321) crystal planes of SnO2 (PDF#41-1445), respectively, and the remaining characteristic peaks belong to RuO2 (PDF#40-1290). Compared with Example 1, p-RuSnO x The diffraction peak of RuO2 becomes broadened, indicating that the introduction of Sn element may lead to poor crystallinity of the catalyst.

[0052] Depend on Figure 3 It can be seen that the p-RuErO prepared in Example 3 x The powder material is the same as that in Example 1, and is still composed of RuO2 (PDF#40-1290).

[0053] Depend on Figure 4 It can be seen that the p-RuLaO prepared in Example 4x In the XRD spectrum of p-RuLaO, 38.4°, 42.1° and 44.0° correspond to the (100), (002) and (101) planes of Ru (PDF#06-0663), and the other diffraction peaks correspond to RuO2 (PDF#40-1290). x The catalyst is not completely oxidized after high-temperature calcination, and some Ru still exists.

[0054] Depend on Figure 5 It can be seen that the RuMnZnO prepared in Comparative Example 1 x In the XRD pattern of the catalyst (before acid etching), 31.8°, 34.4°, 36.3°, 47.5°, 56.6°, 62.9° and 67.9° correspond to ZnO (PDF#36-1451), and the remaining diffraction peaks correspond to RuO2 (PDF#40-1290) and Ru (PDF#06-0663), indicating that RuMnZnO before acid etching x The catalyst is composed of Ru, RuO2 and ZnO. x It was observed in the XRD pattern of the catalyst (after acid etching) that the characteristic peak of ZnO disappeared, indicating that acid etching successfully removed ZnO in the catalyst; the diffraction peaks of RuO2 (PDF#40-1290) and Ru (PDF#06-0663) still existed, but the intensity of the RuO2 diffraction peak became higher, indicating that after acid etching, the crystallinity of the catalyst improved.

[0055] The sample prepared in Example 1 was subjected to nitrogen adsorption and desorption test. The test results are as follows: Figure 6 As shown, p-RuGaO after acid etching x It has a porous structure and a large specific surface area of ​​111m 2 / g, average pore size ~4.5nm. The method of acid etching to remove ZnO can obtain a porous catalyst structure, which helps the electrolyte and the catalyst to fully contact during the catalytic process, realize the rapid transfer of charge, promote the mass transfer process of the oxygen evolution reaction, and improve the catalytic activity; the loose porous catalyst structure can also reduce the structural damage caused by gas evolution, provide a more stable structure for the catalyst, and improve the working stability of the catalyst in an acidic oxidizing environment.

[0056] p-RuGaO prepared in Example 1 of the present invention x The membrane electrode was prepared as an anode catalyst and its electrolytic performance was tested in a single electrolyzer. The test results are as follows Figure 7 shown.

[0057] The preparation process of the membrane electrode is as follows: first, 5 mL of water, 5 mL of isopropanol, 5 g of 5% Nafion solution and 350 mg of fully ground p-RuGaO xThe catalyst powder was added into a ball mill to prepare ink; after magnetic stirring for 30 minutes, 80 g of grinding balls were added and ball milled at a speed of 350 r / min for 12 hours; then a membrane electrode was prepared on the surface of the Nafion membrane by spray transfer.

[0058] Depend on Figure 7 It can be seen that 100mA / cm 2 The cell voltage is 1.47V at the current density of 500mA / cm 2 The cell voltage is 1.58V at a current density of 1A / cm 2 The cell voltage is 1.68V at the current density. Due to its excellent electron conductivity and specific surface area, it has excellent catalytic activity as an anode catalyst in PEM electrolyzer.

[0059] The ruthenium-based oxide powder materials prepared in Examples 1 to 5 and Comparative Example 1 were used to conduct an electrocatalytic oxygen evolution reaction performance test in a 0.5 mol / L sulfuric acid electrolyte. The test results are as follows: Figure 8 And as shown in Table 1.

[0060] The test method is as follows: first prepare the catalyst ink, mix 10mg catalyst, 35μL Nafion solution, and 480μL isopropanol, and stir for 12h. While the glassy carbon disc electrode is rotating slowly and evenly, 8μL of the above-mentioned stirred and dispersed ink is dripped on the electrode until the solvent evaporates completely. Connect the glassy carbon disc electrode head to the CHI-660E electrochemical workstation, the electrolyte is 0.5mol / L sulfuric acid solution, immerse the dripped electrode in the electrolyte, and test the current change of the disc electrode in the potential range of 1.3 to 1.8V RHE.

[0061] Table 1

[0062] <![CDATA[Overpotential (mV @ 10 mA / cm 2 )]]> Example 1 200 Example 2 280 Example 3 220 Example 4 260 Example 5 300 Comparative Example 1 370

[0063] Depend on Figure 8 It can be seen that the samples prepared in Examples 1 to 5 and Comparative Example 1 have certain catalytic activity for oxygen evolution reaction under acidic conditions. 2 At the current density of 10 mA / cm, the overpotential is only 200 mV, which has excellent catalytic activity for oxygen evolution reaction. 2 At the current density, the overpotential is 280mV, and the catalytic activity of oxygen evolution reaction is slightly poor; the sample of Example 3 is at 10mA / cm 2 At the current density, the overpotential is 220mV, and the catalytic activity of oxygen evolution reaction is excellent; the sample of Example 4 is at 10mA / cm 2 At the current density, the overpotential is 260mV, and the catalytic activity of oxygen evolution reaction is good; the sample of Example 5 is at 10mA / cm 2Under the current density, the overpotential is 300mV, and the catalytic activity of oxygen evolution reaction is slightly poor; the sample of comparative example 1 is not acid etched, and the overpotential is 300mV under the current density of 10mA / cm 2 Under the current density, the overpotential is 370mV, and the catalytic activity of oxygen evolution reaction is the worst.

[0064] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms may be for different embodiments or examples. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, unless they are contradictory.

[0065] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0066] Although the embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the claims and their equivalents.

Claims

1. A method for preparing a porous ruthenium-based oxide, It is characterized in that The following steps are involved: (a) adding a ruthenium salt, a metal M precursor salt and a zinc salt in a molar ratio of 1:(0.2-2):(1-2) to a solvent, ultrasonically mixing to prepare a precursor solution, and drying to obtain a precursor mixture, wherein the metal M is a transition metal or a rare earth metal; (b) calcining the precursor mixture to obtain a ruthenium-based oxide, denoted as RuMZnO x ; (c) etching the ruthenium-based oxide powder in a sulfuric acid solution with a molar ratio of 0.5 to 3, centrifugally washing and drying to obtain a porous ruthenium-based oxide, denoted as p-RuMO x .

2. The method according to claim 1, It is characterized in that The transition metal includes at least one of gallium, indium, tin, bismuth, manganese, zinc, nickel, cobalt, molybdenum, copper, titanium, vanadium, chromium, niobium, tantalum, and tungsten.

3. The method according to claim 1, It is characterized in that The rare earth metal includes at least one of lanthanum, cerium, erbium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, thulium, ytterbium, lutetium, scandium, and yttrium.

4. The method according to claim 1, It is characterized in that The metal M precursor salt includes nitrate, chloride or acetate with a concentration of 0.1 to 500 mmol / L.

5. The method according to claim 1, It is characterized in that In the step (a), the ultrasonic time is 20 to 120 minutes, the drying temperature is 60° C. to 120° C., and the drying time is 1 to 6 hours.

6. The method according to claim 1, It is characterized in that In the step (b), the calcination temperature is 250° C. to 850° C., and the calcination time is 1 to 5 hours.

7. The method according to claim 1, It is characterized in that In the step (c), the etching temperature is 60° C. to 90° C., and the etching time is 1 to 12 hours.

8. The method according to claim 1, It is characterized in that The concentration of the sulfuric acid solution is 0.01-1 mol / L.

9. A porous ruthenium-based oxide, It is characterized in that The porous ruthenium-based oxide is prepared by the method according to any one of claims 1 to 8, and the pore size of the porous ruthenium-based oxide is 0.1 to 5 nm.

10. Use of the porous ruthenium-based oxide prepared by the method according to any one of claims 1 to 8 or the porous ruthenium-based oxide according to claim 9 in proton membrane electrolyzers and fuel cell anti-reverse electrodes.

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