Ruthenium molybdenum oxide nanorod electrocatalyst, preparation method and application

Abstract

The invention belongs to the technical field of water electrolysis hydrogen production catalysis, and particularly relates to a ruthenium molybdenum oxide nanorod electrocatalyst, a preparation method and application. In the electrocatalyst, the molar ratio of Mo to Ru is 1: 1-1: 9, and Mo atoms enter ruthenium oxide crystal lattices in the form of replacing Ru atoms; the method comprises the following steps: adding ammonium-containing molybdenum salt and NaNO3 crystals into a ruthenium salt solution, drying, grinding, calcining in air, cooling, and washing with deionized water to remove the NaNO3 crystals to obtain the electrocatalyst. According to the preparation method of the electrocatalyst, the problems of poor stability, high cost, complicated preparation and the like in the preparation process of an anode end catalyst in a proton exchange membrane water electrolysis hydrogen production technology are solved, the prepared electrocatalyst presents an ultra-small nanorod morphology, and a large number of edge and corner sites are generated for an oxygen production reaction; the Ru-O coordination structure of the electrocatalyst is in an unsaturated state, the Ru-O covalent interaction is significantly weakened, the introduction of Mo with low electronegativity inhibits the excessive oxidation of the electrocatalyst, and the oxygen production stability is high.

Description

Technical Field

[0001] The present invention relates to the technical field of hydrogen production by electrolyzing water catalysis, and particularly relates to a ruthenium molybdenum oxide nanorod electrocatalyst, a preparation method and an application thereof. Background Art

[0002] With the increasing consumption of traditional fossil fuels such as coal, oil and natural gas, a large amount of carbon dioxide is released, posing a serious threat to the human living environment. It is urgent to get rid of the dependence on traditional fossil fuels and actively develop new clean alternative energy sources. Hydrogen energy, as a clean, efficient, safe and sustainable new energy, has the advantages of high energy density, zero pollution and zero carbon emissions, and is an inevitable trend for building a clean energy system. There are various hydrogen production processes. Among them, electrolyzing water driven by renewable energy to produce green hydrogen is an effective way to achieve green and low-carbon transformation and solve energy problems. The key to promoting the practical application of hydrogen production by electrolyzing water lies in the development of electrolysis water technology with high electrolysis efficiency and low cost.

[0003] Proton exchange membrane electrolysis of water has high electrolysis efficiency and current density, and is the mainstream technology for hydrogen production by electrolyzing water at present, and has been applied to commercial production of green hydrogen. However, a large amount of high-cost precious metal iridium (1098 - 1112 yuan / gram) is required for its anode, which greatly limits the development of this technology. The lower-cost precious metal ruthenium (119 - 149 yuan / gram) has better oxygen evolution activity than iridium, and is considered promising to replace iridium oxide-based materials for acidic oxygen evolution reaction (OER). Nevertheless, the synthesis steps of ruthenium oxide-based materials are often relatively complex, and over-oxidation often occurs at high current densities, oxidizing from low-valence Ru 0 or Ru 4+ to high-valence Ru x+ (such as RuO4) and dissolving in the electrolyte, facing serious problems such as catalyst deactivation. In the prior art, mainly through doping methods to enhance the electron density around Ru atoms on the surface of ruthenium oxide-based materials, thereby preventing their over-oxidation. However, the dissolution and loss of doping elements will gradually oxidize ruthenium atoms in ruthenium oxide-based materials, which is not sufficient to support its long-term stable acidic oxygen evolution. There are few studies starting from the surface geometric configuration of ruthenium oxide, by reducing the Ru-O coordination number to weaken the Ru-O covalent interaction, thereby inhibiting the dissolution of Ru in the lattice and fundamentally improving the long-term stability of ruthenium oxide-based materials. To sum up, how to design the surface geometric configuration of ruthenium oxide to precisely regulate its Ru-O covalent interaction, while developing low-cost, highly efficient and stable ruthenium oxide-based material acidic oxygen evolution electrocatalysts, is still an urgent problem to be solved.

[0004] In the prior art, the invention with the patent publication number CN119433598A and the name "A highly stable multivalent metal surface-doped ruthenium-based catalyst and its preparation method and application" discloses a stable multivalent metal surface-doped ruthenium oxide catalyst, its preparation method, and its application in a proton exchange membrane water electrolysis device. By doping multivalent metals such as molybdenum, niobium, tungsten, tantalum, chromium, etc. into ruthenium oxide, flexible valence changes are achieved, effectively stabilizing the electronic structure of the active center. At the same time, surface doping constructs a special surface layer, inhibiting the detachment of the active center Ru and lattice oxygen, thus having the advantages of low cost and good catalytic stability. However, among them, multivalent metals such as molybdenum are only incorporated into ruthenium oxide in the surface form and are prone to dissolution at high current densities, making it difficult to support its long-term stable acidic oxygen evolution at high current densities.

[0005] In the prior art, the invention with the patent publication number CN119265608A and the name "A dual-transition-metal-doped RuO2 acidic OER electrocatalyst and its preparation method and application" obtains an electrocatalyst through hydrothermal reaction and annealing treatment, and its chemical formula is (M1) x (M2) y RuO2, where M1 is Zr or Ti; M2 is Mo, Nb, or Tc; x and y are both 0.02 - 0.1. This dual-doping strategy realizes the regulation of the electron density of the active site Ru and forms oxygen vacancies during the reaction, thereby increasing the role of the active sites on the catalyst surface and improving the electrochemical stability of the material. However, the prepared electrocatalyst is in the shape of particles, with a relatively high surface Ru-O coordination number, unable to effectively reduce the Ru-O covalent interaction, and can only perform the electrolytic water oxygen evolution reaction for 200 h at a current density as low as 10 mA cm -2 and cannot meet the requirements of the long-term stable operation of proton exchange membrane water electrolysis. Summary of the Invention

[0006] To overcome the above-mentioned shortcomings of the prior art, the purpose of the present invention is to propose a ruthenium molybdenum oxide nanorod electrocatalyst, a preparation method, and an application. This method uses an ammonium-containing molybdate salt to directionally regulate the growth of the crystal plane of ruthenium molybdenum oxide in a sodium nitrate molten salt environment, inducing the formation of a nanorod morphology with a specific orientation, achieving the purpose of exposing abundant edge and corner active sites of ruthenium molybdenum oxide. In the prepared ruthenium molybdenum oxide nanorod electrocatalyst, the Ru-O coordination structure is in an unsaturated state, significantly weakening the Ru-O covalent interaction. At the same time, the introduction of low electronegativity Mo increases the Ru electron density on the catalyst surface to inhibit its overoxidation, solving the problems of poor stability, high cost, and cumbersome preparation of the anode catalyst in the proton exchange membrane water electrolysis hydrogen production technology.

[0007] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0008] In a first aspect, a ruthenium molybdenum oxide nanorod electrocatalyst, the electrocatalyst being ruthenium molybdenum oxide with a nanorod morphology, and the molar ratio of Mo to Ru in the ruthenium molybdenum oxide being 1:1 to 1:9, and Mo atoms enter the ruthenium oxide lattice in the form of replacing Ru atoms.

[0009] In a second aspect, a method for preparing a ruthenium molybdenum oxide nanorod electrocatalyst, comprising the following steps:

[0010] S1: Add an ammonium molybdate salt and NaNO3 crystals to a ruthenium salt solution and mix and stir to obtain a ruthenium precursor solution, and the molar ratio of Mo, Ru, NO3 - and NH4 + in the ruthenium precursor solution is 1:(1 - 9):(580 - 1740):(0.8 - 2);

[0011] S2: Heat the ruthenium precursor solution obtained in step S1 until the ruthenium precursor solution is evaporated to dryness and the surface shows a dark brown color, and grind the ruthenium molybdenum mixed salt formed after evaporation to dryness into a ruthenium molybdenum mixed salt powder;

[0012] S3: Calcinate the ruthenium molybdenum mixed salt powder obtained in step S2 to form a ruthenium molybdenum mixed salt in a molten salt state, naturally cool the ruthenium molybdenum mixed salt in the molten salt state to room temperature, and then wash the ruthenium molybdenum mixed salt cooled to room temperature with deionized water at least 3 times and dry it to obtain a ruthenium molybdenum oxide nanorod electrocatalyst.

[0013] Further, the ruthenium salt solution in step S1 is an aqueous solution of RuCl3 or K2RuCl6 or C 15 H 21 O6Ru with a Ru ion concentration of 0.01 - 0.1 mol / L.

[0014] Further, the ammonium molybdate salt in step S1 is ammonium molybdate tetrahydrate or ammonium molybdate.

[0015] Further, the mesh number of the ruthenium molybdenum mixed salt powder in step S2 is 200 mesh and above.

[0016] Further, the heating temperature in step S2 is 70 - 90 °C, and the heating time is 24 - 48 h.

[0017] Further, the calcination temperature in step S3 is 350 - 450 °C, and the calcination time is 2 - 4 h.

[0018] In a third aspect, an application of a ruthenium molybdenum oxide nanorod electrocatalyst in proton exchange membrane electrolysis water for hydrogen production.

[0019] Compared with the existing technology, the present invention has the following beneficial effects:

[0020] 1. The ruthenium molybdenum oxide nanorod electrocatalyst in the present invention as a whole exhibits an ultra-small nanorod morphology. The diameter of the nanorods is 3.9 ± 1.1 nm. The nanorods have a large number of edge and corner sites for participating in the OER process, which can not only effectively reduce the Ru-O coordination number and its covalent interaction, but also increase the number of active sites.

[0021] 2. This method uses the NaNO3 molten salt method. By adding an ammonium molybdate salt to the ruthenium salt solution in step S1, and then evaporating to dryness, grinding, calcining and washing, a ruthenium molybdenum oxide with a nanorod structure is formed. Among them, Mo atoms enter the ruthenium oxide lattice in the form of replacing Ru atoms, which not only reduces the usage amount of the precious metal Ru, reduces the raw material cost, but also significantly improves the oxygen evolution activity and stability effect of the Ru active sites in the ruthenium molybdenum oxide. Experiments prove that the ruthenium molybdenum oxide nanorod electrocatalyst prepared by this method has an acidic oxygen evolution overpotential as low as 191 mV at a current density of 10 mA cm -2 When the current density reaches 1 A cm -2 Only a cell voltage of 1.63 V is required, and it can be stable for more than 300 hours, indicating that the ruthenium molybdenum oxide nanorod electrocatalyst in the present invention has relatively high oxygen evolution stability.

[0022] 3. The raw materials used in this method have a low cost and the preparation process is simple. Experiments prove that when the electrocatalyst is coated on the anode of a proton exchange membrane electrolytic water tank with a mass density of 1.8 mg Ru cm -2 , the cost is as low as 0.20 - 0.25 yuan / cm 2 , which can solve the problems of high cost and cumbersome preparation existing in the anode catalyst of the existing proton exchange membrane electrolytic water hydrogen production technology, and is suitable for industrial large-scale production of low-cost acidic OER electrocatalysts.

[0023] In summary, the ruthenium molybdenum oxide nanorod electrocatalyst prepared by this method has rich edge and corner sites on its surface. By introducing Mo with low electronegativity, the excessive oxidation behavior of surface Ru during its OER (oxygen evolution reaction) process is inhibited, greatly improving the oxygen evolution stability of the ruthenium molybdenum oxide nanorod electrocatalyst. At the same time, this method has low raw material cost and simple preparation process, which is convenient for industrial large-scale production. 4+ BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is the transmission electron microscope image of the ruthenium molybdenum oxide nanorod electrocatalyst obtained in Example 1 of the present invention.

[0025] Figure 2 It is the spherical aberration transmission electron microscope image of the ruthenium molybdenum oxide nanorod electrocatalyst obtained in Example 1 of the present invention.

[0026] Figure 3 X-ray diffraction (XRD) patterns of the ruthenium molybdenum oxide nanorod electrocatalyst obtained in Example 1 of the present invention and commercial RuO2.

[0027] Figure 4 Ru 3d X-ray photoelectron spectroscopy (XPS) images of the ruthenium molybdenum oxide nanorod electrocatalyst obtained in Example 1 of the present invention and commercial RuO2.

[0028] Figure 5 Linear sweep voltammetry (LSV) curves of the ruthenium molybdenum oxide nanorod electrocatalyst obtained in Example 1 of the present invention and commercial RuO2 under a three-electrode system.

[0029] Figure 6 Stability test curves of the ruthenium molybdenum oxide nanorod electrocatalyst obtained in Example 1 of the present invention and commercial RuO2 under a three-electrode system.

[0030] Figure 7 Proton exchange membrane water electrolysis polarization curves with the ruthenium molybdenum oxide nanorod electrocatalyst obtained in Example 1 of the present invention and commercial RuO2 as anodes, respectively.

[0031] Figure 8 Large current stability test curve of proton exchange membrane water electrolysis with the ruthenium molybdenum oxide nanorod electrocatalyst obtained in Example 1 of the present invention as an anode.

[0032] Figure 9 Linear sweep voltammetry curve of the ruthenium molybdenum oxide nanorod electrocatalyst obtained in Example 2 of the present invention under a three-electrode system.

[0033] Figure 10 Linear sweep voltammetry curve of the ruthenium molybdenum oxide nanorod electrocatalyst obtained in Example 3 of the present invention under a three-electrode system.

[0034] Figure 11 Linear sweep voltammetry curve of the ruthenium oxide electrocatalyst obtained in Comparative Example 1 of the present invention under a three-electrode system. Detailed Description of the Invention

[0035] The following is a further detailed description of the present invention in conjunction with Figures 1 to 11 :

[0036] The present invention aims to provide a method for preparing a ruthenium molybdenum oxide nanorod electrocatalyst for long-term stable hydrogen production by proton exchange membrane electrolysis of water at a high current density. In the present invention, ammonium ions and molybdenum ions are introduced into the molten NaNO3 salt, and the growth of ruthenium molybdenum oxide is directionally controlled by ammonium ions to form a nanorod morphology, which contains a large number of unsaturated Ru-O sites such as edges and corners; at the same time, molybdenum forms a ruthenium molybdenum oxide solid solution in the form of occupying ruthenium atoms, successfully increasing the electron density of Ru on the catalyst surface to inhibit its excessive oxidation, thereby solving problems such as the rapid dissolution of ruthenium oxide-based materials at a high current density. This method not only has a low cost and simple synthesis, but also can ensure that the designed ruthenium molybdenum oxide nanorod electrocatalyst has both activity and stability, and has great application value.

[0037] In a first aspect, a ruthenium molybdenum oxide nanorod electrocatalyst, the electrocatalyst is ruthenium molybdenum oxide with a nanorod morphology, and the nanorod morphology exposes abundant edge and corner active sites, reducing the Ru-O coordination number and significantly weakening the Ru-O covalent interaction; the molar ratio of Mo to Ru in the ruthenium molybdenum oxide is 1:1 to 1:9, and the introduced low electronegativity Mo atoms enter the ruthenium oxide lattice in the form of replacing Ru atoms, increasing the Ru electron density on the electrocatalyst surface and inhibiting its excessive oxidation behavior, so that the oxygen evolution stability of the electrocatalyst in an acidic medium is significantly improved.

[0038] In a second aspect, a method for preparing a ruthenium molybdenum oxide nanorod electrocatalyst, comprising the following steps:

[0039] S1. Prepare a ruthenium precursor solution: Add an ammonium molybdate salt and NaNO3 crystals to a ruthenium salt solution and mix and stir to obtain a ruthenium precursor solution. After the ruthenium precursor solution is fully stirred until completely dissolved, the molar ratio of Mo, Ru, NO3 - and NH4 + in the completely dissolved ruthenium precursor solution is 1:(1 - 9):(580 - 1740):(0.8 - 2);

[0040] S2. Grind the ruthenium molybdenum mixed salt powder: Put the completely dissolved ruthenium precursor solution obtained in step S1 into an oven and heat it. After drying at a temperature of 70 - 90 °C for 24 - 48 h until the ruthenium precursor solution is evaporated and the surface shows a dark brown color, grind the ruthenium molybdenum mixed salt formed after evaporation into a ruthenium molybdenum mixed salt powder with 200 meshes or more;

[0041] S3. Preparation of ruthenium molybdenum oxide nanorod electrocatalyst: Put the ruthenium molybdenum mixed salt powder described in step S2 into a crucible and calcine it. Under an air atmosphere, control the temperature at 350 - 450 °C and calcine the ruthenium molybdenum mixed salt powder for 2 - 4 h to form a ruthenium molybdenum mixed salt in a completely flowable molten salt state. Let the ruthenium molybdenum mixed salt in the molten salt state cool naturally to room temperature. At this time, ruthenium molybdenum oxide is embedded in the cooled solid NaNO3 crystal in the form of particles. Then wash the ruthenium molybdenum mixed salt cooled to room temperature with deionized water at least 3 times to remove the NaNO3 crystals. After washing, dry the remaining powder to obtain the ruthenium molybdenum oxide nanorod electrocatalyst.

[0042] Further, the ruthenium salt solution is RuCl3 or K2RuCl6 or C with a Ru ion concentration of 0.01 - 0.1 mol / L 15 H 21 O6Ru aqueous solution.

[0043] Further, the ammonium - containing molybdate salt in step S1 is ammonium molybdate tetrahydrate ((NH4)6Mo7O 24 ·4H2O) or ammonium molybdate ((NH4)2MoO4).

[0044] In the third aspect, an application of a ruthenium molybdenum oxide nanorod electrocatalyst in proton - exchange membrane electrolytic water for hydrogen production.

[0045] The present invention is further illustrated by the following examples: According to the following examples, the present invention can be better understood. However, those skilled in the art can easily understand that the specific material ratios, process conditions and their results described in the examples are only used to illustrate the present invention, and should not and will not limit the present invention described in detail in the claims.

[0046] Example 1

[0047] A ruthenium molybdenum oxide nanorod electrocatalyst, the electrocatalyst is ruthenium molybdenum oxide with a nanorod morphology, and the molar ratio of Mo to Ru in the ruthenium molybdenum oxide is 2:8. The specific preparation method is as follows:

[0048] A preparation method of a ruthenium molybdenum oxide nanorod electrocatalyst, comprising the following steps:

[0049] Step 1): Prepare a ruthenium precursor solution: Add 5 g of NaNO3 and (NH4)6Mo7O 24 ·4H2O with a molar ratio of Mo to Ru of 2:8 to an aqueous solution of RuCl3 with a volume of 20 mL and a Ru ion concentration of 0.02 mol / L, and stir well until completely dissolved;

[0050] Step 2), grinding the ruthenium-molybdenum mixed salt powder: Place the ruthenium precursor solution in an oven and dry it at 90 °C for 24 hours. Then take it out and grind it with a mortar to obtain a ruthenium-molybdenum mixed salt powder in which the ruthenium-molybdenum precursor is uniformly dispersed on the surface of NaNO3 crystals;

[0051] Step 3), preparing a ruthenium-molybdenum oxide nanorod electrocatalyst: Put the ruthenium-molybdenum mixed salt powder obtained in Step 2 into a crucible and calcine it at 350 °C for 2 hours in an air atmosphere. After it naturally cools to room temperature, wash it 3 times with deionized water to remove the NaNO3 salt crystals. After drying, a ruthenium-molybdenum oxide nanorod electrocatalyst is obtained.

[0052] As Figure 1 shown, the electrocatalyst as a whole presents an ultra-small nanorod morphology. The diameter of the nanorods is about 3.9 ± 1.1 nm, and there are a large number of edge and corner sites for participating in the OER process. It can not only effectively reduce the Ru-O coordination number and its covalent interaction, but also increase the number of active sites; as Figure 2 shown, the (110) crystal plane of RuO2 can be observed in the spherical aberration transmission electron microscope image, and the lattice spacing is 0.318 nm, indicating that the ruthenium-molybdenum oxide forms a solid solution, which is consistent with the lattice arrangement of RuO2. Among them, Mo atoms enter the RuO2 lattice in the form of replacing Ru atoms.

[0053] As Figure 3 shown, the ruthenium-molybdenum oxide nanorods have the same diffraction peak positions as commercial RuO2, which again confirms that the type of its lattice structure has not changed; at the same time, compared with commercial RuO2, the full width at half maximum of the diffraction peak of the ruthenium-molybdenum oxide nanorods is significantly increased, corresponding to its ultra-small nanorod-like grain size.

[0054] As Figure 4 shown, the Ru 3d peaks in the ruthenium-molybdenum oxide nanorods form Ru 4+ :Ru 3+ of 0.57, which is significantly lower than 1.41 of commercial RuO2, meaning that the electron density around Ru in this electrocatalyst has increased, thus inhibiting the excessive oxidation behavior of Ru.

[0055] Prepare the ruthenium-molybdenum oxide nanorod electrocatalyst prepared in Example 1 above into a slurry, drop it onto a rotating disk electrode as a working electrode, and place it in a three-electrode system for performance testing; among them, the counter electrode is a carbon rod, the reference electrode is Hg / Hg2SO4, and the electrolyte is a H2SO4 solution with a concentration of 0.5 mol / L; as Figure 5 shown, after the water electrolysis performance test, the scanning rate is 5 mV / s, and IR compensation is carried out through the solution internal resistance measured by EIS; as Figure 6 shown, at a current density of 10 mAcm -2At this time, the overpotential of the electrocatalyst is as low as 191 mV, and it can operate stably for more than 100 hours, indicating that the ruthenium molybdenum oxide nanorod electrocatalyst has excellent oxygen evolution activity and stability.

[0056] As Figure 7 shown, the polarization curve of proton exchange membrane water electrolysis with the ruthenium molybdenum oxide nanorod electrocatalyst as the anode is presented. As Figure 8 shown, at a current density of 1 A cm -2 , the cell voltage is only 1.63 V, and it can operate stably for more than 300 hours. The above electrochemical performance tests indicate that by constructing an ultra-small nanorod morphology and introducing a low electronegativity Mo element to prepare ruthenium molybdenum oxide, not only can excellent acidic OER activity be obtained, but also the rapid inactivation problem of RuO2-based materials at high current densities can be successfully solved, showing excellent potential for industrial applications.

[0057] Through the water electrolysis performance test, the ruthenium molybdenum oxide nanorod electrocatalyst has excellent oxygen evolution activity and stability. When the current density of this electrocatalyst is 10 mA cm -2 , the overpotential is only 191 mV. When the current density reaches 1 A cm -2 , only a cell voltage of 1.63 V is required, and it can be stable for more than 300 hours.

[0058] Example 2

[0059] A ruthenium molybdenum oxide nanorod electrocatalyst, the electrocatalyst is ruthenium molybdenum oxide with a nanorod morphology, and the molar ratio of Mo to Ru in the ruthenium molybdenum oxide is 1:9. The specific preparation method is as follows:

[0060] A preparation method of a ruthenium molybdenum oxide nanorod electrocatalyst, comprising the following steps:

[0061] Step 1), Prepare a ruthenium precursor solution: Add 5 g of NaNO3 and (NH4)6Mo7O 24 ·4H2O to an aqueous RuCl3 solution with a volume of 30 mL and a Ru ion concentration of 0.02 mol / L, where the molar ratio of Mo to Ru is 1:9, and stir well until completely dissolved;

[0062] Step 2), Grind the ruthenium molybdenum mixed salt powder: Place the ruthenium precursor solution in an oven, dry it at 90 °C for 48 hours, then take it out and grind it with a mortar to obtain a ruthenium molybdenum mixed salt powder in which the ruthenium molybdenum precursor is uniformly dispersed on the surface of NaNO3 crystals;

[0063] Step 3), Preparation of ruthenium molybdenum oxide nanorod electrocatalyst: Put the ruthenium molybdenum mixed salt powder obtained in Step 2 into a crucible, calcine it at 350 °C for 2 hours in an air atmosphere. After it naturally cools to room temperature, wash it 3 times with deionized water to remove NaNO3 salt crystals. After drying, obtain the ruthenium molybdenum oxide nanorod electrocatalyst.

[0064] As Figure 9 shown, at a current density of 10 mA cm -2 , compared with Example 1, the overpotential of this electrocatalyst slightly increases to 200 mV; this indicates that the reduction of the Mo salt amount will reduce the acidic OER activity of the ruthenium molybdenum oxide nanorods.

[0065] Example 3

[0066] A ruthenium molybdenum oxide nanorod electrocatalyst, the electrocatalyst is ruthenium molybdenum oxide with a nanorod morphology, and the molar ratio of Mo to Ru in the ruthenium molybdenum oxide is 5:5. The specific preparation method is as follows:

[0067] A preparation method of a ruthenium molybdenum oxide nanorod electrocatalyst, comprising the following steps:

[0068] Step 1), Preparation of ruthenium precursor solution: Add 10 g of NaNO3 and (NH4)6Mo7O 24 ·4H2O to an aqueous RuCl3 solution with a volume of 25 mL and a Ru ion concentration of 0.04 mol / L, where the molar ratio between Mo and Ru is 5:5, and stir well until completely dissolved;

[0069] Step 2), Grinding of ruthenium molybdenum mixed salt powder: Place the ruthenium precursor solution in an oven, dry it at 90 °C for 24 hours, then take it out and grind it with a mortar to obtain a ruthenium molybdenum mixed salt powder in which the ruthenium molybdenum precursor is uniformly dispersed on the surface of NaNO3 crystals;

[0070] Step 3), Preparation of ruthenium molybdenum oxide nanorod electrocatalyst: Put the ruthenium molybdenum mixed salt powder obtained in Step 2 into a crucible, calcine it at 350 °C for 2 hours in an air atmosphere. After it naturally cools to room temperature, wash it 3 times with deionized water to remove NaNO3 salt crystals. After drying, obtain the ruthenium molybdenum oxide nanorod electrocatalyst.

[0071] As Figure 10 shown, at a current density of 10 mA cm -2 , compared with Example 1, the overpotential of this electrocatalyst also shows an upward trend, being 204 mV. This indicates that excessive increase in the Mo salt content will reduce the number of surface Ru active sites, thereby reducing the acidic OER activity.

[0072] Example 4

[0073] A ruthenium molybdenum oxide nanorod electrocatalyst, wherein the electrocatalyst is ruthenium molybdenum oxide with a nanorod morphology, wherein the molar ratio of Mo to Ru in the ruthenium molybdenum oxide is 2:8, and the specific preparation method is as follows:

[0074] A method for preparing a ruthenium molybdenum oxide nanorod electrocatalyst comprises the following steps:

[0075] Step 1), prepare a ruthenium precursor solution: add 15g NaNO3 and (NH4)2MoO4 to a 50mL K2RuCl6 aqueous solution with a Ru ion concentration of 0.06mol / L, wherein the molar ratio of Mo to Ru is 2:8, and stir thoroughly until completely dissolved;

[0076] Step 2), grinding ruthenium-molybdenum mixed salt powder: placing the ruthenium precursor solution in an oven, drying it at 90° C. for 24 hours, taking it out and grinding it in a mortar to obtain a ruthenium-molybdenum mixed salt powder in which the ruthenium-molybdenum precursor is evenly dispersed on the surface of the NaNO3 crystal;

[0077] Step 3) Prepare ruthenium molybdenum oxide nanorod electrocatalyst: put the ruthenium molybdenum mixed salt powder obtained in step 2 into a crucible, calcine it at 350°C for 2 hours in an air atmosphere, wait for it to cool naturally to room temperature, wash it with deionized water three times to remove NaNO3 salt crystals, and after drying, obtain a ruthenium molybdenum oxide nanorod electrocatalyst.

[0078] Example 5

[0079] A ruthenium molybdenum oxide nanorod electrocatalyst, wherein the electrocatalyst is ruthenium molybdenum oxide with a nanorod morphology, wherein the molar ratio of Mo to Ru in the ruthenium molybdenum oxide is 3:7, and the specific preparation method is as follows:

[0080] A method for preparing a ruthenium molybdenum oxide nanorod electrocatalyst comprises the following steps:

[0081] Step 1) Prepare ruthenium precursor solution: add 10g NaNO3 and (NH4)6Mo7O to a 30mL RuCl3 aqueous solution with a Ru ion concentration of 0.02mol / L. 24 4H2O, where the molar ratio of Mo to Ru is 3:7, and stirred thoroughly until completely dissolved;

[0082] Step 2), grinding ruthenium-molybdenum mixed salt powder: placing the ruthenium precursor solution in an oven, drying it at 70° C. for 48 hours, taking it out and grinding it in a mortar to obtain a ruthenium-molybdenum mixed salt powder in which the ruthenium-molybdenum precursor is evenly dispersed on the surface of the NaNO3 crystal;

[0083] Step 3): Prepare a ruthenium molybdenum oxide nanorod electrocatalyst: Put the ruthenium molybdenum mixed salt powder obtained in Step 2 into a crucible, calcine it at 350 °C for 4 hours in an air atmosphere, wait for it to cool naturally to room temperature, wash it 3 times with deionized water to remove NaNO3 salt crystals, and after drying, obtain a ruthenium molybdenum oxide nanorod electrocatalyst.

[0084] Example 6

[0085] A ruthenium molybdenum oxide nanorod electrocatalyst, the electrocatalyst is a ruthenium molybdenum oxide with a nanorod morphology, and the molar ratio of Mo to Ru in the ruthenium molybdenum oxide is 2:8. The specific preparation method is as follows:

[0086] A preparation method of a ruthenium molybdenum oxide nanorod electrocatalyst, comprising the following steps:

[0087] Step 1): Prepare a ruthenium precursor solution: Add 5 g of NaNO3 and (NH4)6Mo7O 15 H 21 to an aqueous solution of C 24 O6Ru with a volume of 5 mL and a Ru ion concentration of 0.01 mol / L, where the molar ratio between Mo and Ru is 2:8, and stir well until completely dissolved;

[0088] Step 2): Grind the ruthenium molybdenum mixed salt powder: Place the ruthenium precursor solution in an oven, dry it at 90 °C for 48 hours, then take it out and grind it with a mortar to obtain a ruthenium molybdenum mixed salt powder in which the ruthenium molybdenum precursor is uniformly dispersed on the surface of NaNO3 crystals;

[0089] Step 3): Prepare a ruthenium molybdenum oxide nanorod electrocatalyst: Put the ruthenium molybdenum mixed salt powder obtained in Step 2 into a crucible, calcine it at 450 °C for 2 hours in an air atmosphere, wait for it to cool naturally to room temperature, wash it 3 times with deionized water to remove NaNO3 salt crystals, and after drying, obtain a ruthenium molybdenum oxide nanorod electrocatalyst.

[0090] Example 7

[0091] A ruthenium molybdenum oxide nanorod electrocatalyst, the electrocatalyst is a ruthenium molybdenum oxide with a nanorod morphology, and the molar ratio of Mo to Ru in the ruthenium molybdenum oxide is 1:9. The specific preparation method is as follows:

[0092] A preparation method of a ruthenium molybdenum oxide nanorod electrocatalyst, comprising the following steps:

[0093] Step 1): Prepare a ruthenium precursor solution: Add 15 g of NaNO3 and (NH4)6Mo7O 24·4H2O, where the molar ratio between Mo and Ru is 1:9, and stir well until completely dissolved;

[0094] Step 2), grinding the ruthenium-molybdenum mixed salt powder: Place the ruthenium precursor solution in an oven, dry it at 90 °C for 48 hours, then take it out and grind it with a mortar to obtain a ruthenium-molybdenum mixed salt powder with the ruthenium-molybdenum precursor evenly dispersed on the surface of NaNO3 crystals;

[0095] Step 3), preparing the ruthenium-molybdenum oxide nanorod electrocatalyst: Put the ruthenium-molybdenum mixed salt powder obtained in Step 2 into a crucible, calcine it at 450 °C for 4 hours in an air atmosphere, wait for it to cool naturally to room temperature, then wash it 3 times with deionized water to remove the NaNO3 salt crystals, and after drying, obtain the ruthenium-molybdenum oxide nanorod electrocatalyst.

[0096] Example 8

[0097] A ruthenium-molybdenum oxide nanorod electrocatalyst, the electrocatalyst is ruthenium-molybdenum oxide with a nanorod morphology, and the molar ratio of Mo to Ru in the ruthenium-molybdenum oxide is 4:6. The specific preparation method is as follows:

[0098] A preparation method of a ruthenium-molybdenum oxide nanorod electrocatalyst, comprising the following steps:

[0099] Step 1), preparing a ruthenium precursor solution: Add 10 g of NaNO3 and (NH4)6Mo7O 24 ·4H2O to an aqueous solution of K2RuCl6 with a volume of 40 mL and a Ru ion concentration of 0.08 mol / L, where the molar ratio between Mo and Ru is 4:6, and stir well until completely dissolved;

[0100] Step 2), grinding the ruthenium-molybdenum mixed salt powder: Place the ruthenium precursor solution in an oven, dry it at 80 °C for 36 hours, then take it out and grind it with a mortar to obtain a ruthenium-molybdenum mixed salt powder with the ruthenium-molybdenum precursor evenly dispersed on the surface of NaNO3 crystals;

[0101] Step 3), preparing the ruthenium-molybdenum oxide nanorod electrocatalyst: Put the ruthenium-molybdenum mixed salt powder obtained in Step 2 into a crucible, calcine it at 400 °C for 3 hours in an air atmosphere, wait for it to cool naturally to room temperature, then wash it 4 times with deionized water to remove the NaNO3 salt crystals, and after drying, obtain the ruthenium-molybdenum oxide nanorod electrocatalyst.

[0102] Comparative Example 1 Preparation of ruthenium oxide electrocatalyst by molten salt method

[0103] Step 1), preparing a ruthenium chloride salt solution: Add 5 g of NaNO3 to an aqueous solution of RuCl3 with a volume of 20 mL and a Ru ion concentration of 0.02 mol / L, and stir well until completely dissolved;

[0104] Step 2), grinding ruthenium chloride salt powder: Place the ruthenium chloride salt solution in an oven and dry it at 90 °C for 24 hours. Then take it out and grind it in a mortar to obtain a black-brown powder in which RuCl3 is uniformly dispersed on the surface of NaNO3 crystals;

[0105] Step 3), preparing ruthenium oxide electrocatalyst: Put the black-brown powder obtained in Step 2 into a crucible and calcine it at 350 °C for 2 hours in an air atmosphere. After it naturally cools to room temperature, wash it 3 times with deionized water to remove NaNO3 salt crystals. After drying, ruthenium oxide electrocatalyst is obtained.

[0106] From Figure 11 It can be clearly seen that the activity of this ruthenium oxide electrocatalyst is far lower than that of the ruthenium molybdenum oxide nanorod electrocatalyst in Example 1. At a current density of 10 mA cm -2 , the overpotential rises to 214 mV, indicating that the introduction of Mo is crucial for improving the activity of the ruthenium oxide electrocatalyst.

[0107] Working principle:

[0108] The preparation method of the present invention uses an improved sodium nitrate molten salt method to prepare a ruthenium molybdenum oxide nanorod electrocatalyst, which uniformly disperses metal ruthenium atoms and molybdenum atoms in a molten salt environment, avoiding the agglomeration of molybdenum oxide particles, and enabling molybdenum to form a ruthenium molybdenum oxide solid solution in a way that replaces ruthenium; at the same time, the introduced molybdenum salt contains ammonium ions, which can be directionally combined with its crystal plane at the nucleation stage of ruthenium molybdenum oxide, and regulate the growth of the ruthenium molybdenum oxide crystal plane through directional adsorption, thereby inducing the formation of a nanorod morphology with a specific orientation; the obtained ruthenium molybdenum oxide nanorod electrocatalyst surface has rich edge and corner sites for oxygen evolution reaction, making the Ru-O coordination structure in an unsaturated state, significantly weakening the Ru-O covalent interaction, thereby optimizing the adsorption process of oxygen evolution reaction intermediates, and the introduction of low electronegativity Mo can enhance the charge density around Ru atoms, effectively inhibiting the 4+ over-oxidation of the active center during the OER process, significantly improving the stability of the catalyst in acidic media. Compared with the traditional preparation process, the preparation method of the present invention has mild reaction conditions and does not require complex post-treatment, and the single-batch output can reach the gram scale, having significant cost advantages and industrial production potential, providing a new strategy for the development of highly efficient and stable acidic oxygen evolution electrocatalysts.

Claims

1. A ruthenium molybdenum oxide nanorod electrocatalyst, characterized in that, The electrocatalyst is ruthenium molybdenum oxide with a nanorod morphology. In the ruthenium molybdenum oxide, the molar ratio of Mo to Ru is from 1:1 to 1:9, and Mo atoms enter the ruthenium oxide lattice in the form of replacing Ru atoms.

2. A preparation method of a ruthenium molybdenum oxide nanorod electrocatalyst, characterized in that, It includes the following steps: S1: Add ammonium molybdenum salt and NaNO3 crystals to the ruthenium salt solution and mix and stir to obtain a ruthenium precursor solution. The ruthenium precursor solution contains Mo, Ru, and NO3 - and NH4 + The molar ratio is 1:(1-9):(580-1740):(0.8-2); S2: Heat the ruthenium precursor solution in step S1 until the ruthenium precursor solution is evaporated to dryness and the surface shows a dark brown color. Grind the ruthenium molybdenum mixed salt formed after evaporation to dryness into a ruthenium molybdenum mixed salt powder. S3: Calcinate the ruthenium molybdenum mixed salt powder in step S2 to form a ruthenium molybdenum mixed salt in a molten salt state. Naturally cool the ruthenium molybdenum mixed salt in the molten salt state to room temperature, and then wash the ruthenium molybdenum mixed salt cooled to room temperature with deionized water at least 3 times and then dry it to obtain a ruthenium molybdenum oxide nanorod electrocatalyst.

3. The preparation method according to claim 2, characterized in that, The ruthenium salt solution described in step S1 is an aqueous solution of RuCl3 or K2RuCl6 or C 15 H 21 O6Ru with a Ru ion concentration of 0.01 - 0.1 mol / L.

4. The preparation method according to claim 2, characterized in that The ammonium molybdate salt in step S1 is ammonium molybdate tetrahydrate or ammonium molybdate.

5. The preparation method according to claim 2, characterized in that, The mesh number of the ruthenium molybdenum mixed salt powder in step S2 is 200 mesh and above.

6. The preparation method according to claim 2, wherein, The heating temperature in step S2 is 70 - 90 °C, and the heating time is 24 - 48 h.

7. The preparation method according to claim 2, characterized in that, The calcination temperature in step S3 is 350 - 450 °C, and the calcination time is 2 - 4 h.

8. The ruthenium molybdenum oxide nanorod electrocatalyst according to claim 1, wherein In the electrocatalyst, the molar ratio of Mo to Ru is 2:

8.

9. The preparation method according to claim 2, characterized in that, In the ruthenium precursor solution in step S1, the molar ratio of Mo to Ru is 2:

8. The heating temperature in step S2 is 90 °C, and the heating time is 24 h. The calcination temperature in step S3 is 350 °C, and the calcination time is 2 h.

10. Application of a ruthenium molybdenum oxide nanorod electrocatalyst in proton exchange membrane electrolytic water for hydrogen production.

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