Ruthenium-based solid solution oxide catalyst, preparation method and application

Abstract

The invention discloses a ruthenium-based solid solution oxide catalyst as well as a preparation method and application thereof, and the ruthenium-based solid solution oxide catalyst is prepared by adopting an acid-resistant metal (Ti, Nb, Mo, W and Ta) substrate material and ruthenium salt to synthesize a ruthenium-based precursor in situ, and then performing high-temperature calcination in an air atmosphere to prepare the ruthenium-based solid solution oxide catalyst. The prepared ruthenium-based solid solution catalyst has the characteristics of excellent conductivity, small crystal particle size, high crystallinity and the like. Elements of the solid solution catalyst synthesized by the method are good in dispersity, excessive oxidation of ruthenium sites can be effectively inhibited, long-time stability of active sites under strong acid and strong oxidation conditions can be guaranteed, and the solid solution catalyst is expected to be applied to PEM industrial electrolytic water.

Description

Technical Field

[0001] The present application relates to a ruthenium-based solid solution oxide catalyst, a preparation method and an application thereof, and belongs to the fields of electrochemical catalyst technology and new energy technology. Background Art

[0002] Proton exchange membrane (PEM) water electrolysis is a water electrolysis hydrogen production technology with the advantages of fast current response speed, high electrolysis efficiency, wide adjustment range, and high hydrogen purity. It is one of the most popular hydrogen production technologies. PEM water electrolysis hydrogen production technology is due to the strong acidic environment provided by the proton exchange membrane, resulting in only iridium-based catalysts being able to operate stably for a long time under the conditions of the anode oxygen evolution reaction. However, the high price of iridium has severely restricted the large-scale industrial development of PEM water electrolysis.

[0003] Compared to iridium, ruthenium-based catalyst is also a very promising anode material, it has higher acidic oxygen evolution activity, higher earth reserves and market price is only about one tenth of iridium, but ruthenium-based catalyst is easily over-oxidized and then dissolved under acidic oxidation conditions, resulting in poor catalytic stability (CN113277573A). To solve the problem of ruthenium-based catalyst stability, the current development of other metal-doped ruthenium oxide is the most representative, according to the type of doped metal elements can be divided into three categories. One, iridium, rhodium, palladium, platinum, etc. are introduced into the ruthenium oxide lattice, these elements themselves have good corrosion resistance for acidic environment and as active sites of water oxidation, can significantly improve the activity and stability of ruthenium-based catalyst. But these elements are all precious metals, more rare and expensive than ruthenium, resulting in the cost of catalyst to increase, is not conducive to large-scale industrial application of PEM electrolysis of water (CN116356361A). Second, iron, cobalt, nickel and other elements that are not acid-resistant but have water oxidation activity doped ruthenium oxide can effectively change the electronic environment of ruthenium sites, and avoid excessive oxidation of ruthenium sites by oxidative dissolution of itself. Although this approach improves the performance of ruthenium-based catalysts, the elements such as iron, cobalt, and nickel dissolved can block the proton exchange membrane, causing the membrane conductivity to be greatly reduced, thereby affecting the catalyst in the PEM electrolytic cell for a long time catalytic performance (CN113026051A). Third, tantalum, niobium, titanium and other elements doped ruthenium oxide, due to the excellent acid etching resistance of these elements themselves, can effectively improve the stability of ruthenium-based catalysts. However, the poor conductivity of the oxide formed is not conducive to the carrying out of oxygen evolution reaction (CN107740138A). Therefore, developing a kind of efficient, stable and low-cost ruthenium-based anode oxygen evolution catalyst is a difficult problem to be solved in the current PEM electrolysis water technology development. Summary of the invention

[0004] The present invention adopts acid-resistant metal materials as conductive substrates and doping metal sources through reasonable catalyst design and modification, and covers the metal substrate with a layer of ruthenium-based solid solution oxide catalyst through simple hydrothermal method and heat treatment, thereby strengthening the interaction between the catalyst and the substrate, and solving the problems of decreased conductivity caused by metal doping and poor stability of ruthenium sites, thereby achieving a dual improvement in the stability and activity of ruthenium-based catalysts.

[0005] According to one aspect of the present application, a ruthenium-based solid solution oxide catalyst is provided, wherein the chemical formula of the ruthenium-based solid solution oxide catalyst is RuMO x ,

[0006] M is selected from one of Ti, Nb, Mo, W and Ta;

[0007] Wherein, x is the mole fraction, and the value of x is 0.05 to 0.5.

[0008] Optionally, the particle size of the ruthenium-based solid solution oxide catalyst is 1 to 10 nm.

[0009] Optionally, the particle size of the ruthenium-based solid solution oxide catalyst is independently selected from any value of 1 nm, 2 nm, 3 nm, 4 nm, 5 nm, 6 nm, 7 nm, 8 nm, 9 nm, 10 nm or a range between any two of the above values.

[0010] Optionally, in the ruthenium-based solid solution oxide catalyst, the M replaces the ruthenium site in the ruthenium oxide lattice in the ruthenium-based solid solution oxide catalyst, and M is uniformly dispersed at the atomic level in the ruthenium oxide.

[0011] Optionally, in the ruthenium-based solid solution oxide catalyst, metal heteroatoms (Ti, Nb, Mo, W, Ta) replace ruthenium sites in the ruthenium oxide lattice, the heteroatoms are uniformly dispersed at the atomic level in the ruthenium oxide, the solid solution oxide is small in size and has good crystallinity; the ruthenium-based solid solution oxide is in-situ grown on a metal substrate by hydrothermal etching.

[0012] According to another aspect of the present application, a method for preparing the above-mentioned ruthenium-based solid solution oxide catalyst is provided, and the preparation method comprises the following steps:

[0013] (1) immersing the washed metal substrate in a strong base, performing a hydrothermal treatment for I, and drying for I to obtain an etched metal substrate;

[0014] (2) placing the etched metal substrate in a mixture containing a ruthenium salt and an inorganic acid, and performing a hydrothermal treatment II to obtain a metal substrate on which ruthenium is deposited;

[0015] (3) drying II and calcining the metal substrate on which ruthenium is deposited to obtain a ruthenium-based solid solution oxide catalyst;

[0016] The metal element in the metal substrate is selected from at least one of Ti, Nb, Mo, W and Ta.

[0017] Optionally, the metal substrate is selected from mesh and / or felt.

[0018] Optionally, the mesh size of the net is 50 to 300 meshes.

[0019] Optionally, the mesh size of the net is independently selected from any value of 50 mesh, 100 mesh, 200 mesh, 300 mesh, or a range value between any two of the above.

[0020] Optionally, in step (1), the strong base is selected from at least one of sodium hydroxide, potassium hydroxide, calcium hydroxide and barium hydroxide.

[0021] Optionally, the strong base is selected from sodium hydroxide and / or potassium hydroxide.

[0022] Optionally, the concentration of the strong base is 0.1-10 mol / L.

[0023] Optionally, the concentration of the strong base is independently selected from any value among 0.1 mol / L, 0.5 mol / L, 1 mol / L, 2 mol / L, 5 mol / L, 8 mol / L, 10 mol / L or a range between any two of the above.

[0024] Preferably, the concentration of the strong base is 8 mol / L.

[0025] Optionally, in step (1), the temperature of the hydrothermal treatment I is 25 to 160° C., and the time of the hydrothermal treatment I is 1 to 12 hours.

[0026] Preferably, in step (1), the temperature of the hydrothermal treatment I is 80° C., and the time of the hydrothermal treatment I is 10 hours.

[0027] Optionally, the temperature of the hydrothermal treatment I is independently selected from any value of 25°C, 50°C, 80°C, 100°C, 120°C, 140°C, 160°C or a range between any two of the above values.

[0028] Optionally, the time of the hydrothermal treatment I is independently selected from any value among 1h, 2h, 5h, 8h, 10h, 12h or a range between any two of the above.

[0029] Optionally, the temperature of the drying I is 40 to 100° C., and the time of the drying I is 4 to 12 hours.

[0030] Optionally, in step (2), the ruthenium salt is selected from at least one of ruthenium acetate, ruthenium acetylacetonate, ruthenium chloride, ruthenium trichloride, and ruthenium nitrate.

[0031] Optionally, the concentration of the ruthenium salt is 0.01-0.1 mol / L.

[0032] Optionally, the inorganic acid is selected from at least one of nitric acid, sulfuric acid, hydrochloric acid, hydrofluoric acid, hydrobromic acid and hydroiodic acid.

[0033] Preferably, the inorganic acid is hydrochloric acid.

[0034] Optionally, the concentration of the inorganic acid is 0.01 to 5 mol / L.

[0035] Optionally, the concentration of the inorganic acid is independently selected from any value among 0.01 mol / L, 0.05 mol / L, 0.1 mol / L, 0.5 mol / L, 1 mol / L, 3 mol / L, 5 mol / L or a range between any two of the above.

[0036] Optionally, in step (2), the pH value of the mixture is 0-5.

[0037] Preferably, in step (2), the pH value of the mixture is 5.

[0038] Optionally, in step (2), the temperature of the hydrothermal treatment II is 25 to 160° C., and the time of the hydrothermal treatment II is 1 to 12 hours.

[0039] Preferably, in step (2), the temperature of the hydrothermal treatment II is 100° C., and the time of the hydrothermal treatment II is 8 hours.

[0040] Optionally, the temperature of the hydrothermal treatment II is independently selected from any value of 25°C, 50°C, 80°C, 100°C, 120°C, 140°C, 160°C or a range between any two of the above values.

[0041] Optionally, the time of the hydrothermal treatment II is independently selected from any value of 1 h, 2 h, 5 h, 8 h, 10 h, 12 h, or a range between any two of the above values.

[0042] Optionally, in the step (3), the calcination further includes strong acid treatment and drying III.

[0043] Optionally, the strong acid is selected from at least one of hydrochloric acid, sulfuric acid, perchloric acid and phosphoric acid.

[0044] Preferably, the strong acid is selected from sulfuric acid.

[0045] Optionally, the concentration of the strong acid is 0.5-5 mol / L.

[0046] Optionally, the concentration of the strong acid is independently selected from any value among 0.5 mol / L, 1 mol / L, 3 mol / L, 5 mol / L or a range between any two of the above.

[0047] Optionally, the temperature of the strong acid treatment is 25 to 160° C., and the time of the strong acid treatment is 1 to 10 hours.

[0048] Optionally, the temperature of the strong acid treatment is independently selected from any value of 25°C, 50°C, 80°C, 100°C, 120°C, 140°C, 160°C or a range between any two of the above values.

[0049] Optionally, the time of the strong acid treatment is independently selected from any value of 1 h, 2 h, 5 h, 8 h, 10 h, or a range between any two of the above.

[0050] Optionally, the temperature of the strong acid treatment is 80° C., and the time of the strong acid treatment is 8 hours.

[0051] Optionally, the temperature of the drying III is 40 to 100° C., and the time of the drying III is 4 to 12 hours.

[0052] Optionally, in step (3), the temperature of drying II is 40 to 100° C., and the time of drying II is 4 to 12 hours.

[0053] Optionally, in step (3), the calcination temperature is 200 to 600° C., and the calcination time is 0.5 to 8 hours.

[0054] Preferably, in step (3), the calcination temperature is 400° C. and the calcination time is 2 h.

[0055] Optionally, in step (3), the calcination temperature is independently selected from any value of 200°C, 250°C, 300°C, 350°C, 400°C, 450°C, 500°C, 550°C, 600°C or a range between any two of the above values.

[0056] Optionally, the calcination time is independently selected from any value of 0.5h, 1h, 2h, 4h, 6h, 8h or a range between any two of the above.

[0057] Optionally, the calcination atmosphere is an oxygen-containing atmosphere.

[0058] Optionally, the oxygen content in the oxygen-containing atmosphere is 5-20%.

[0059] In the present application, an acid-resistant metal material is used as an electrode substrate, and the metal surface oxide is dissolved by etching with an acid solution at a high temperature. As the acid solution is consumed, the pH of the solution rises, and the dissolved metal ions and ruthenium ions are co-deposited on the surface of the metal substrate to form a ruthenium-based precursor, and then the crystallinity of the surface ruthenium-based solid solution oxide is improved by high-temperature calcination in an air atmosphere. The acid-resistant metal material is one or more of Ti, Nb, Mo, W, and Ta, preferably Ti. The catalyst obtained is RuTiO x , is a layer of ruthenium titanium solid solution oxide covered on the surface of a metal Ti substrate. The preparation method of the ruthenium-based solid solution oxide catalyst comprises the following steps:

[0060] (1) Alkaline etching treatment: The metal substrate was ultrasonically washed in the order of ethanol, isopropanol, acetone, and ethanol for 30 minutes; the washed titanium mesh substrate was immersed in a prepared strong alkaline aqueous solution for hydrothermal treatment; the treated titanium substrate was repeatedly washed with deionized water until neutral, and dried in an oven at 80°C overnight.

[0061] (2) Hydrothermal etching co-deposition: The treated metal substrate is placed in an aqueous solution of ruthenium salt, and an appropriate acid solution is added to adjust the pH to a suitable range. After ultrasonic treatment for 1 hour, hydrothermal treatment is performed.

[0062] (3) High temperature annealing: The obtained metal substrate is placed in an oven at 80°C for drying and then calcined at high temperature in an air atmosphere; the calcined titanium metal substrate is placed in a strong acid solution for treatment, repeatedly washed with deionized water until neutral, and placed in an oven at 80°C for drying.

[0063] According to another aspect of the present application, there is provided a use of the above-mentioned ruthenium-based solid solution oxide catalyst in PEM water electrolysis.

[0064] The present invention adopts transition metal elements (Ti, Nb, Mo, W, Ta) to dope ruthenium oxide, firstly avoiding the high catalyst cost caused by noble metal doping, and secondly the corrosion resistance of the selected transition metal elements themselves will not affect the long-term test performance of the PEM membrane electrode. The traditional element doping synthesis method is high-temperature pyrolysis, high-temperature melting of caustic soda and sol-gel, and the prepared catalyst has a large microscopic scale, and due to the difference in oxidation temperature and crystallization temperature between ruthenium and transition metal elements, the dispersibility of transition metal elements is not good and is often accompanied by the precipitation of crystalline phase, resulting in a decrease in catalyst conductivity, and then a decrease in catalyst activity. The present invention breaks this inertial thinking and adopts a method of hydrothermal etching of a metal substrate to co-deposit ruthenium ions and metal ions to form a ruthenium-based precursor, significantly enhancing the interaction between the conductive substrate and the catalyst, improving the electron transport capacity, and then performing high-temperature calcination to improve the crystallinity of the catalyst to obtain a saturated coordinated ruthenium site, and finally preparing a ruthenium-based solid solution oxide catalyst. Therefore, the ruthenium-based solid solution oxide catalyst in the present invention can significantly improve the intrinsic activity and long-term stability of the ruthenium site.

[0065] The beneficial effects of this application include:

[0066] 1) The catalyst provided in the present application is a ruthenium-based solid solution oxide dispersed at the atomic scale, in which ruthenium and metal exist in the form of a high-crystallinity solid solution oxide. The X-ray diffraction pattern has an obvious rutile structure diffraction peak, and the main diffraction peak is offset to a high angle or a low angle due to the doping of metal elements and the difference between its own ionic radius and ruthenium. In addition, the catalyst prepared by the synthesis method has the characteristics of small particle size, uniform dispersion, high crystallinity, etc., and can provide more active area and more stable active sites.

[0067] 2) The ruthenium-based solid solution oxide catalyst prepared in this application has good oxygen production activity and excellent stability under acidic conditions, reaching 10 mA / cm 2 The current density only needs an overpotential of 198mV, and the current density is between 50 and 200mA / cm 2 It can operate stably for 800 and 700 hours respectively under different current densities. Compared with commercial ruthenium oxide catalysts, it has better intrinsic activity and better long-term stability. The introduction of metal can significantly reduce the amount of precious metal ruthenium and save the cost of catalyst preparation.

[0068] 3) The hydrothermal etching method provided in the present application grows the acid-resistant element-doped ruthenium oxide in situ on the metal material, and effectively avoids the reduction of the conductivity of ruthenium oxide due to doping by strengthening the interaction between the conductive substrate and the catalyst, which is not conducive to the oxygen evolution reaction. At the same time, the Ru-OM site formed can effectively change the electronic environment of ruthenium, making the ruthenium site more electron-rich, which is conducive to the transmission of electrons and improves the performance of the catalyst; secondly, the doping of heteroatoms increases the Ru-O bond, making O 2p The Fermi level of the orbital is significantly reduced, preventing the lattice oxygen in ruthenium oxide from participating in the oxygen evolution reaction, effectively improving the stability of the catalyst. BRIEF DESCRIPTION OF THE DRAWINGS

[0069] Figure 1 Schematic diagram of the ruthenium-based solid solution oxide catalyst in Examples 1 to 4 of the present application.

[0070] Figure 2 The RuTiO calcined at 100°C, 200°C, 300°C, 400°C, and 500°C in Example 1 of the present application x Linear voltammetric scanning activity test graph in 0.5 mol / L sulfuric acid solution.

[0071] Figure 3 The RuTiO calcined at 100°C, 200°C, 300°C, 400°C, and 500°C in Example 1 of the present application x The catalyst is in a 0.5 mol / L sulfuric acid solution with a constant 50 mA / cm 2 Graph of the current density chronovoltage stability test.

[0072] Figure 4 The RuTiO calcined at 400°C in Example 1 of this application x And the linear voltammetric scanning activity test graphs of RuO2 / TiO2, RuO2 / Ti and commercial RuO2 prepared in comparative examples 1-3 in 0.5 mol / L sulfuric acid solution.

[0073] Figure 5 The RuTiO calcined at 400°C in Example 1 of this application x The constant 50 mA / cm2 of RuO2 / TiO2, RuO2 / Ti and commercial RuO2 prepared in 0.5 mol / L sulfuric acid solution 2 Graph of the current density chronovoltage stability test.

[0074] Figure 6 The RuTiO calcined at 400°C in Example 1 of this application x Constant 200mA / cm in 0.5mol / L sulfuric acid solution 2 Graph of the current density chronovoltage stability test.

[0075] Figure 7 The RuTiO calcined at 400°C in Example 1 of this application x And the RuTiO prepared in Comparative Example 4 x (Drop coating) in 0.5 mol / L sulfuric acid solution (a is the linear voltammetric scanning activity test diagram and b is the AC impedance diagram).

[0076] Figure 8 The RuTiO calcined at 400°C in Example 1 of this application x , X-ray diffraction (XRD) patterns of RuO2 / Ti and titanium substrate prepared in Comparative Example 2.

[0077] Fig. 9 The RuTiO calcined at 400°C in Example 1 of this application x Transmission electron microscopy (TEM), scale is 20nm, (a is the catalyst morphology, b is the catalyst size distribution).

[0078] Fig.10 The RuTiO calcined at 400°C in Example 1 of this application x High-resolution transmission electron microscopy (HR-TEM), the scale is 1nm, (a is a high-angle annular dark field transmission electron microscopy image, b is the Ru element mapping on RuTiO x distribution on RuTiO, c is the Ti element mapping x distribution on RuTiO, d is the mapping of Ru and Ti elements on RuTiO x distribution on ).

[0079] Fig.11 The RuTaO obtained by hydrothermal etching in 0.25, 0.5, 1, and 2 mol / L nitric acid solutions in Example 3 of the present application is shown in FIG. x Linear voltammetric scanning activity test graph in 0.5 mol / L sulfuric acid solution.

[0080] Fig.12 The RuTaO obtained by hydrothermal etching in 0.25 mol / L nitric acid solution in Example 3 of the present application x Constant 50 mA / cm in 0.5 mol / L sulfuric acid solution 2 Graph of the current density chronovoltage stability test. DETAILED DESCRIPTION

[0081] The present application is described in detail below with reference to embodiments, but the present application is not limited to these embodiments.

[0082] Unless otherwise specified, the raw materials in the examples of this application were purchased through commercial channels.

[0083] This application uses a CHI-760e instrument for electrochemical testing, a Shimadzu D / Max-2400 instrument for XRD characterization, and a FEI Talos F200s instrument for transmission electron microscopy characterization.

[0084] Example 1

[0085] This example illustrates the ruthenium-based solid solution oxide catalyst (RuTiO x An example of preparation and control of calcination temperature.

[0086] The titanium substrate was ultrasonically washed in ethanol, isopropanol, acetone, and ethanol for 30 minutes in sequence. The washed titanium substrate was immersed in the prepared 8 mol / L sodium hydroxide aqueous solution and hydrothermally treated at 60°C for 8 hours. The treated titanium substrate was repeatedly washed with deionized water until neutral and dried in an oven at 80°C overnight. The treated titanium substrate was placed in a 0.03 mol / L ruthenium acetate solution, and a 2 mol / L hydrochloric acid solution was added to adjust the pH to about 0.5. After ultrasonic treatment for 1 hour, it was hydrothermally treated at 100°C for 12 hours.

[0087] The obtained titanium substrate was placed in an oven at 80°C for drying and then heated to 100°C, 200°C, 300°C, 400°C and 500°C for calcination for 2 hours in an air atmosphere to obtain a series of precursors treated at different annealing temperatures. The calcined precursor was placed in a 6 mol / L hydrochloric acid solution at 100°C for 2 hours, repeatedly washed with deionized water until neutral, and placed in an oven at 80°C for drying to prepare RuTiO x Catalyst, average particle size is 4.78nm.

[0088] like Figure 2 As shown, Figure 2 RuTiO calcined at 100℃, 200℃, 300℃, 400℃, and 500℃ x The linear voltammetric scanning activity test graph in 0.5 mol / L sulfuric acid solution shows that as the calcination temperature increases, the catalyst gradually agglomerates, resulting in a decrease in the active area, which is not conducive to the reaction.

[0089] like Figure 3 As shown, Figure 3 RuTiO calcined at 100℃, 200℃, 300℃, 400℃, and 500℃ x The catalyst is in a 0.5 mol / L sulfuric acid solution with a constant 50 mA / cm 2 The current density chronovoltage stability test graph shows that with the increase of calcination temperature, a highly crystalline ruthenium-based solid solution oxide is gradually formed, and its saturated coordinated ruthenium sites are more conducive to long-term stability.

[0090] like Figure 6 As shown, RuTiO calcined at 400 °C x Constant 200mA / cm in 0.5mol / L sulfuric acid solution 2 Current density chronovoltage stability test diagram, from Figure 6 It can be seen that the catalyst has excellent stability even at high current density, and the oxygen production activity shown under higher oxidation conditions is almost unchanged.

[0091] like Fig. 9 As shown, RuTiO calcined at 400 °C x The transmission electron microscope image shows that the catalyst is nanoparticles with a size distribution between 1 and 10 nm and an average size of 4.78 nm.

[0092] like Fig.10 As shown, RuTiO calcined at 400 °C x High-resolution transmission electron microscopy images of Fig.10 In d, it can be seen that Ru and Ti are evenly distributed in the same phase, and Ru has a higher proportion, confirming that the catalyst structure is Ti-doped RuO x Solid solution.

[0093] Example 2

[0094] This example illustrates the ruthenium-based solid solution oxide catalyst (RuMoO x An example of the preparation and control of ruthenium content of .

[0095] The molybdenum substrate was ultrasonically washed in ethanol, isopropanol, acetone, and ethanol for 30 minutes in sequence. The washed molybdenum substrate was immersed in a prepared 10 mol / L potassium hydroxide aqueous solution and treated at 80°C for 2 hours. The treated molybdenum substrate was repeatedly washed with deionized water until neutral and dried in an oven at 80°C overnight. The treated molybdenum substrate was placed in 0.01 mol / L, 0.02 mol / L, 0.03 mol / L, 0.04 mol / L, and 0.05 mol / L ruthenium acetylacetonate solutions, respectively, and 2 mol / L nitric acid solution was added to adjust the pH to about 3. After ultrasonic treatment for 1 hour, it was hydrothermally treated at 100°C for 12 hours.

[0096] The obtained molybdenum substrate was placed in an oven at 80°C for drying and then heated to 500°C for calcination for 4 hours in an air atmosphere to obtain a series of precursors treated at different annealing temperatures. The calcined precursor was placed in a 6 mol / L hydrochloric acid solution at 100°C for 2 hours, repeatedly washed with deionized water until neutral, and placed in an oven at 80°C for drying to obtain RuMoO x catalyst.

[0097] Example 3

[0098] This example illustrates the ruthenium-based solid solution oxide catalyst (RuTaO x An example of the preparation and control of tantalum content of tantalum.

[0099] The tantalum substrate was ultrasonically washed in the order of ethanol, isopropanol, acetone, and ethanol for 30 minutes. The washed tantalum substrates were immersed in the prepared 10 mol / L potassium hydroxide aqueous solution, hydrothermally treated at 100°C for 12 hours. The treated tantalum substrate was repeatedly washed with deionized water until neutral, and dried in an oven at 80°C overnight. The treated tantalum substrate was placed in 0.25, 0.5, 1, and 2 mol / L nitric acid solutions, and 0.07 mol / L ruthenium chloride was added. After ultrasonic treatment for 1 hour, it was hydrothermally treated at 100°C for 12 hours.

[0100] The obtained tantalum substrate was placed in an oven at 80°C for drying and then heated to 350°C for 6 hours in an air atmosphere to obtain a series of precursors treated at different annealing temperatures. The calcined precursor was placed in a 6 mol / L hydrochloric acid solution at 100°C for 2 hours, repeatedly washed with deionized water until neutral, and placed in an oven at 80°C for drying to obtain RuTaO x catalyst.

[0101] like Fig.11 As shown, Fig.11 The RuTaO obtained by treatment with nitric acid solutions of different concentrations (0.25, 0.5, 1, 2 mol / L) x The linear voltammetric scanning activity test graph of the catalyst in 0.5 mol / L sulfuric acid solution shows that with the increase of acid concentration, the amount of dissolved tantalum ions and ruthenium co-deposition decreases, resulting in a decrease in the number of active sites of the catalyst, which is not conducive to the oxygen evolution reaction.

[0102] like Fig.12 As shown, RuTaO x Constant 50 mA / cm in 0.5 mol / L sulfuric acid solution 2 Current density chronovoltage stability test diagram, from Fig.12 It can be seen that RuTaO x It also has excellent stability in acidic oxygen-generating reactions.

[0103] Example 4

[0104] This example illustrates the ruthenium-based solid solution oxide catalyst (RuWO x Take the preparation examples of different atmosphere treatments as an example).

[0105] The tungsten substrate was ultrasonically washed in ethanol, isopropanol, acetone, and ethanol for 30 minutes in sequence. The washed tungsten substrate was immersed in a prepared 5 mol / L potassium hydroxide aqueous solution and hydrothermally treated at 60°C for 8 hours. The treated tungsten substrate was repeatedly washed with deionized water until neutral and dried in an oven at 80°C overnight. The treated tungsten substrate was placed in a 0.01 mol / L ruthenium trichloride aqueous solution, and a 2 mol / L phosphoric acid solution was added to adjust the pH to about 3. After ultrasonication for 1 hour, it was hydrothermally treated at 100°C for 10 hours to obtain precursors with different Ru contents.

[0106] The obtained tungsten substrate was placed in an oven at 80°C for drying and then heated to 450°C for calcination for 1 hour in argon, nitrogen, hydrogen, and air atmospheres. The calcined precursor was placed in a 6 mol / L hydrochloric acid solution at 100°C for 2 hours, repeatedly washed with deionized water until neutral, and placed in an oven at 80°C for drying to prepare RuWO x catalyst.

[0107] like Figure 1 Schematic diagram of ruthenium-based solid solution oxide catalyst shown in the figure; the metal substrate after alkaline etching is placed in a specific acid solution and is continuously etched, causing the oxide on the surface to dissolve, and the metal releases hydrogen when in contact with the acid, ensuring that the substrate surface is not covered with oxide; at the same time, as the acid is consumed, the pH of the solution gradually increases, and the ruthenium ions and metal ions in the solution are co-deposited and cover the surface of the metal substrate to form a ruthenium-based precursor; finally, through high-temperature calcination, a ruthenium-based solid solution oxide with high crystallinity is formed.

[0108] Example 5

[0109] This example illustrates the ruthenium-based solid solution oxide catalyst (ruthenium niobium oxide solid solution RuNbO x An example of the preparation and control of hydrothermal acid etching conditions.

[0110] The niobium substrate was ultrasonically washed in ethanol, isopropanol, acetone, and ethanol for 30 minutes in sequence. The washed niobium substrates were immersed in the prepared 6 mol / L potassium hydroxide aqueous solution, hydrothermally treated at 100°C for 12 hours. The treated niobium substrate was repeatedly washed with deionized water until neutral, and dried in an oven at 80°C overnight. The treated niobium substrate was placed in a 0.05 mol / L ruthenium nitrate solution, and a 2 mol / L hydrochloric acid solution was added, and the pH was adjusted to 0, 0.5, 1, 2, 3, 4, and 5, respectively. After ultrasonic treatment for 1 hour, the substrate was hydrothermally treated at 100°C for 12 hours.

[0111] The obtained niobium substrate was placed in an oven at 80°C for drying and then heated to 500°C for calcination for 4 hours in an air atmosphere to obtain a series of precursors treated at different annealing temperatures. The calcined precursor was placed in a 6 mol / L hydrochloric acid solution at 100°C for 2 hours, repeatedly washed with deionized water until neutral, and placed in an oven at 80°C for drying to obtain RuNbO x catalyst.

[0112] Comparative Example 1

[0113] This example illustrates the preparation of RuO2 / TiO2 catalyst.

[0114] The titanium substrate was ultrasonically washed in ethanol, isopropanol, acetone, and ethanol in order for 30 minutes. The washed titanium substrate was immersed in the prepared 1mol / L nitric acid and 1mol / L hydrochloric acid aqueous solutions, and hydrothermally treated at 60°C for 8 hours. The treated titanium substrate was repeatedly washed with deionized water until neutral, and dried in an 80°C oven overnight. The treated titanium substrate was placed in a 1mol / L hydrochloric acid solution and hydrothermally treated at 100°C for 24 hours. The obtained titanium substrate was dried in an oven at 80°C and then heated to 400°C in an air atmosphere and calcined for 1 hour to prepare a TiO2 / Ti precursor.

[0115] The TiO2 / Ti precursor was placed in a 0.07 mol / L ruthenium acetate solution, hydrothermally treated at 100°C for 12 hours, dried in an oven at 80°C, and calcined at 400°C for 1 hour in an air atmosphere. The calcined precursor was placed in a 6 mol / L hydrochloric acid solution at 100°C for 2 hours, repeatedly washed with deionized water until neutral, and dried in an oven at 80°C to prepare a RuO2 / TiO2 catalyst.

[0116] Comparative Example 2

[0117] This example illustrates the preparation of RuO2 / Ti catalyst.

[0118] The titanium substrate was ultrasonically washed in ethanol, isopropanol, acetone, and ethanol for 30 minutes in sequence, and dried in an oven at 80°C overnight. The treated titanium substrate was placed in an aqueous solution of ruthenium acetate, ultrasonicated for 1 hour, hydrothermally treated at 100°C for 12 hours, and dried in an oven at 80°C to obtain a precursor.

[0119] The precursor was calcined at 400°C for 2 hours in an air atmosphere, placed in a 6 mol / L hydrochloric acid solution at 100°C for 2 hours, repeatedly washed with deionized water until neutral, and dried in an oven at 80°C to prepare a RuO2 / Ti catalyst. Figure 8 It can be seen that the peak of the ruthenium-based solid solution oxide shifts to a higher angle with respect to the 110 crystal plane of ruthenium oxide, which is caused by the smaller radius of the titanium ion than that of the ruthenium ion.

[0120] Comparative Example 3

[0121] This example illustrates the preparation of a commercial RuO2 catalyst.

[0122] Take 5 mg of rutile anhydrous ruthenium oxide produced by MacLean Company, disperse it in 480 μL ethanol, 480 μL deionized water and 40 μL 5 wt% naphthol solution, ultrasonicate for 2 hours, take 50 μL and drop it on a titanium substrate (1×1 cm 2 ) and dried in an oven at 80°C for 1 hour to obtain a commercial RuO2 catalyst.

[0123] Comparative Example 4

[0124] This example illustrates RuTiO x Example of preparation of (drip-coated) catalyst.

[0125] Take the prepared RuTiO x The catalyst (containing titanium substrate) was 600 mg, placed in 50 ml of deionized water and ultrasonicated for 12 hours, the precipitate was collected by centrifugation, and placed in an oven at 80 ° C to dry overnight to obtain RuTiO x Powder. Take 5 mg of dried RuTiO x The powder was dispersed in 480uL ethanol, 480uL deionized water and 40uL 5wt% naphthol solution, ultrasonicated for 2 hours, and 50uL was dropped on a titanium substrate (1×1cm 2 ) and dried in an oven at 80°C for 1 hour to obtain RuTiO x (Drop coating) catalyst. Figure 7 In the RuTiO calcined at 400 °C x and RuTiO x (Drop coating) Linear voltammetric scanning activity test graph and AC impedance graph in 0.5 mol / L sulfuric acid solution. x After being ultrasonically removed from the titanium substrate, it was re-dropped on the titanium substrate, resulting in a decrease in oxygen evolution activity and an increase in impedance, indicating that the in-situ grown RuTiO x The excellent electron transfer ability between the catalyst and the conductive substrate is conducive to the oxygen evolution reaction.

[0126] Performance Testing Methods

[0127] The anode catalysts obtained in Example 1, Example 3, Comparative Example 1, Comparative Example 2, Comparative Example 3 and Comparative Example 4 were respectively used in a 0.5 mol / L sulfuric acid solution, using a three-electrode system (anode as a working electrode, platinum sheet as a counter electrode, and mercury-mercurous sulfate as a reference electrode) and a 50 mL H-type electrolytic cell as a reactor for oxygen evolution reaction.

[0128] The specific reaction conditions are as follows: the electrolyte is 0.5 mol / L sulfuric acid solution, the electrolysis reaction temperature is 25°C, the rotation speed is 300 rpm, oxygen is introduced for 30 minutes before the test until saturated, and the electrode is activated by cyclic voltammetry, the activity test scan rate is 5 mV / s, and the linear voltammetry activity test is performed; at 50 mA / cm 2 The stability test of the chronopotentiometry was carried out at the current density.

[0129] From the above test results, if Figure 4 As shown, the RuTiO prepared in Example 1 x The catalyst has significantly higher catalytic activity and stability than the RuO2 / TiO2, RuO2 / Ti and commercial RuO2 catalysts prepared in Comparative Examples 1 to 3. In the same linear voltammetry test activity curve and chronovoltammetry test, RuTiO x The solid solution catalyst only needs 198mV overpotential to reach 10mA / cm 2 The current density is between 50 and 200 mA / cm 2 The current density can be stably operated for 800 and 700 hours respectively.

[0130] like Figure 5 As shown, at a constant 50mA / cm 2 In the current density chronovoltage stability test, the RuTiO x The potential of the catalyst changes little within 50 hours. The RuTiO prepared by calcination at 100℃ and 200℃ x The catalyst's potential suddenly increased within 3 hours and 30 hours, resulting in a loss of activity. This is because the ruthenium oxide formed by low-temperature calcination has low crystallinity and unsaturated coordinated ruthenium sites, resulting in poor stability. The RuO2 / TiO2, RuO2 / Ti and commercial RuO2 catalysts prepared in Comparative Examples 1 to 3 suddenly increased their potential within 10 hours, 20 hours and 40 hours, respectively, resulting in a loss of activity. The RuTaO prepared in Example 3 x 230mV overpotential is required to reach 10mA / cm 2 The current density is 50mA / cm 2 The prepared RuTiO x The catalyst performance is better than the current RuO2 / TiO2, RuO2 / Ti and commercial RuO2 catalysts, and the synthesis method has good universality, and can obtain highly active and highly stable ruthenium-based solid solution oxide catalysts on different metal materials. It has important guiding value in the development of future PEM water electrolysis anode oxygen evolution catalysts.

[0131] The above are only a few embodiments of the present application and do not constitute any form of limitation to the present application. Although the present application is disclosed as above with preferred embodiments, it is not intended to limit the present application. Any technician familiar with the profession, without departing from the scope of the technical solution of the present application, using the technical content disclosed above to make slight changes or modifications are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A ruthenium-based solid solution oxide catalyst, characterized in that: The chemical formula of the ruthenium-based solid solution oxide catalyst is RuMO x , M is selected from one of Ti, Nb, Mo, W and Ta; Wherein, x is the mole fraction, and the value of x is 0.05 to 0.

5.

2. The ruthenium-based solid solution oxide catalyst according to claim 1, characterized in that The particle size of the ruthenium-based solid solution oxide catalyst is 1 to 10 nm; Preferably, in the ruthenium-based solid solution oxide catalyst, M replaces the ruthenium sites in the ruthenium oxide lattice in the ruthenium-based solid solution oxide catalyst, and M is uniformly dispersed at the atomic level in the ruthenium oxide.

3. The method for preparing the ruthenium-based solid solution oxide catalyst according to any one of claims 1 to 2, characterized in that: The preparation method comprises the following steps: (1) immersing the washed metal substrate in a strong base, performing a hydrothermal treatment for I, and drying for I to obtain an etched metal substrate; (2) placing the etched metal substrate in a mixture containing a ruthenium salt and an inorganic acid, and performing a hydrothermal treatment II to obtain a metal substrate on which ruthenium is deposited; (3) drying II and calcining the metal substrate on which ruthenium is deposited to obtain a ruthenium-based solid solution oxide catalyst; The metal element in the metal substrate is selected from at least one of Ti, Nb, Mo, W and Ta.

4. The preparation method according to claim 3, characterized in that: In step (1), the strong base is selected from at least one of sodium hydroxide, potassium hydroxide, calcium hydroxide and barium hydroxide; Preferably, the concentration of the strong base is 0.1 to 10 mol / L; Preferably, in step (1), the temperature of the hydrothermal treatment I is 25 to 160° C., and the time of the hydrothermal treatment I is 1 to 12 hours; Preferably, the temperature of the drying I is 40 to 100° C., and the time of the drying I is 4 to 12 hours.

5. The preparation method according to claim 3, characterized in that: In the step (2), the ruthenium salt is selected from at least one of ruthenium acetate, ruthenium acetylacetonate, ruthenium chloride, ruthenium trichloride, and ruthenium nitrate; Preferably, the concentration of the ruthenium salt is 0.01 to 0.1 mol / L; Preferably, the inorganic acid is selected from at least one of nitric acid, sulfuric acid, hydrochloric acid, hydrofluoric acid, hydrobromic acid and hydroiodic acid; Preferably, the concentration of the inorganic acid is 0.01 to 5 mol / L; Preferably, in step (2), the pH value of the mixture is 0-5.

6. The preparation method according to claim 3, characterized in that: In the step (2), the temperature of the hydrothermal treatment II is 25 to 160° C., and the time of the hydrothermal treatment II is 1 to 12 hours.

7. The preparation method according to claim 3, characterized in that: In the step (3), the calcination further comprises strong acid treatment and drying III; Preferably, the strong acid is selected from at least one of hydrochloric acid, sulfuric acid, perchloric acid and phosphoric acid; Preferably, the concentration of the strong acid is 0.5-5 mol / L.

8. The preparation method according to claim 7, characterized in that: The temperature of the strong acid treatment is 25 to 160° C., and the time of the strong acid treatment is 1 to 10 hours; Preferably, the temperature of the drying III is 40 to 100° C., and the time of the drying III is 4 to 12 hours.

9. The preparation method according to claim 3, characterized in that: In the step (3), the temperature of drying II is 40 to 100° C., and the time of drying II is 4 to 12 hours; Preferably, in step (3), the calcination temperature is 200 to 600° C., and the calcination time is 0.5 to 8 h; Preferably, the calcination atmosphere is an oxygen-containing atmosphere; Preferably, the oxygen content in the oxygen-containing atmosphere is 5-20%.

10. Use of the ruthenium-based solid solution oxide catalyst according to any one of claims 1 to 2 in PEM water electrolysis.

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