Heterojunction catalyst composed of cobalt-copper co-doped ruthenium dioxide and metal ruthenium as well as preparation method and application of heterojunction catalyst

Abstract

The invention relates to the technical field of electrocatalysts, and discloses a heterojunction catalyst composed of cobalt-copper co-doped ruthenium dioxide and metal ruthenium as well as a preparation method and application of the heterojunction catalyst. The preparation method comprises the following steps: carrying out hydrothermal reaction on cobalt salt and trimesic acid in a mixed solvent to prepare a cobalt metal organic framework precursor; a cobalt-copper bimetal organic framework is obtained through ion exchange of a copper salt solution; preparing a ruthenium-cobalt-copper ternary metal organic framework by adopting secondary ion exchange of a ruthenium salt solution; and carrying out air calcination treatment to obtain the cobalt-copper co-doped ruthenium dioxide and metal ruthenium heterojunction catalyst. According to the method, cobalt and copper atoms are uniformly doped in ruthenium dioxide crystal lattices through a step-by-step ion exchange strategy, and metal ruthenium nano-particles are grown on the surface in situ to form a heterogeneous interface. The obtained catalyst shows excellent performance in an acidic electrolyzed water anode oxygen evolution reaction, the overpotential is only 199 mV under the current density of 10 mA. Cm, and the stability can be maintained for 40 hours.

Description

Technical Field

[0001] The present invention relates to the technical field of electrocatalysts, and specifically relates to a heterojunction catalyst composed of cobalt and copper co-doped ruthenium dioxide and metallic ruthenium, and a preparation method and application thereof. Background Art

[0002] As an important way to obtain hydrogen, the electrolytic water hydrogen production technology is regarded as a highly promising green and sustainable hydrogen production method due to its wide source of raw material water, high purity of hydrogen product, relatively simple preparation process, mild reaction conditions and clean and pollution-free whole process. Currently, the proton exchange membrane electrolytic water (PEM) technology stands out among many electrolytic water hydrogen production technologies. It has advantages such as high electrolysis efficiency, compact device structure and strong adaptability to the fluctuations of renewable energy, and has become a hot research and application direction. However, during the actual operation of the PEM electrolytic cell, the oxygen evolution catalyst layer on the anode side faces severe challenges. Since a large amount of hydrogen ions are generated during the oxygen evolution reaction process, the catalyst directly loaded on the membrane is in a strongly acidic environment for a long time, and the action of the high oxidation potential also aggravates the corrosion risk of the catalyst. Under such harsh working conditions, the anode oxygen evolution catalyst is extremely easy to be corroded, resulting in a decrease in activity or even inactivation, which severely restricts the large-scale application and development of the PEM electrolytic water hydrogen production technology. Therefore, developing an anode oxygen evolution catalyst with low overpotential, high catalytic activity and excellent corrosion resistance is the key to promoting the breakthrough of the PEM electrolytic water hydrogen production technology.

[0003] In the field of acidic oxygen evolution catalysts, noble metal catalysts represented by ruthenium exhibit certain advantages. They possess good corrosion resistance and catalytic activity, enabling ruthenium and its oxides to occupy an important position in PEM anode oxygen evolution catalysts. However, ruthenium metal resources are scarce and the price is high, which greatly increases the cost of PEM hydrogen production technology and severely limits the large-scale popularization and application of this technology. To solve this problem, researchers have carried out a large amount of research work on improving the activity of ruthenium-based catalysts and reducing the ruthenium metal dosage. For example, some studies have tried to improve the performance of the catalyst by modifying the preparation process and combining ruthenium with other metals. Chinese patent document with publication number CN202210932935.8 discloses a preparation method and use of a transition metal-doped ruthenium oxide nanomaterial. A soluble transition metal source is added to a solution containing a soluble ruthenium source and mixed, then a polymer containing multiple ligand points is added, and the mixture is transferred to a hydrothermal autoclave and kept warm in a constant temperature oven for several hours. The obtained transition metal-containing precursor is placed in a muffle furnace, heated to the required temperature and kept warm for several hours to obtain the transition metal-doped ruthenium oxide nanomaterial. Another example is the Chinese patent document with publication number CN202410938103.6, which discloses a ruthenium-based catalyst and its preparation method. The ruthenium-based catalyst is a porous material. A polysaccharide is used to prepare a first sol, and then a ruthenium source precursor and a complexing agent are used to prepare a ruthenium source solution. The first sol is mixed with the ruthenium source solution to prepare a second sol, and the second sol is dried to obtain an aerogel. Finally, the aerogel is calcined to obtain the ruthenium-based catalyst.

[0004] Although the transition metal doping strategy can optimize the oxygen evolution reaction kinetics of ruthenium oxide-based catalysts by regulating the electronic structure of ruthenium active sites, there are still significant limitations in a single modification method for reducing the noble metal ruthenium loading and breaking through the activity-stability balance bottleneck: on the one hand, it is difficult for single metal doping to simultaneously achieve the dual effects of lattice strain regulation and interfacial charge redistribution, resulting in insufficient exposure of active sites; on the other hand, traditional doping is prone to cause metal aggregation, exacerbating the irreversible oxidative dissolution of high-valent ruthenium species and limiting its long-term operation in strongly acidic media. To address the above problems, the present invention innovatively proposes a dual-metal doping and cooperative heterointerfacial construction strategy: through the co-embedding of cobalt and copper bimetallic atoms into the ruthenium oxide lattice, lattice distortion is induced to expose high-density active sites; at the same time, the in-situ generated ruthenium metal and ruthenium dioxide heterointerfacial is utilized to establish a local electric field to accelerate charge transfer, and the over-oxidation of ruthenium active centers is inhibited through the interfacial coupling effect. By introducing the cobalt-copper co-doping strategy and combining the heterointerfacial design of ruthenium dioxide and ruthenium metal, the present invention not only increases the density of active sites but also improves the carrier separation efficiency, thereby significantly enhancing the oxygen evolution activity of the catalyst. Summary of the Invention

[0005] The present invention focuses on the key problems existing in the existing ruthenium-based catalysts, such as high ruthenium metal loading and poor oxygen evolution activity, and aims to provide a preparation method for a novel heterojunction catalyst composed of cobalt- and copper-codoped ruthenium dioxide and metallic ruthenium. The prepared heterojunction catalyst composed of cobalt- and copper-codoped ruthenium dioxide and metallic ruthenium exhibits excellent electrocatalytic activity in the oxygen evolution reaction at the anode of acidic electrolytic water and has good long-term working stability.

[0006] The present invention provides a preparation method for a heterojunction catalyst composed of cobalt- and copper-codoped ruthenium dioxide and metallic ruthenium. The preparation method specifically includes the following steps: S1. Dissolve a cobalt salt and trimesic acid in a mixed solution, stir and mix evenly, and then obtain a cobalt metal-organic framework precursor through a hydrothermal reaction; S2. Dissolve the cobalt metal-organic framework precursor prepared in step S1 in a methanol solution, and while stirring at room temperature, dropwise add a methanol solution containing a copper salt and trimesic acid, and after mixing evenly, obtain a cobalt-copper metal-organic framework precursor; S3. Dissolve the cobalt-copper metal-organic framework precursor prepared in step S2 in an aqueous solution, and while heating and stirring, dropwise add an aqueous solution containing a ruthenium salt to carry out an ion exchange reaction to obtain a ruthenium-cobalt-copper metal-organic framework precursor; S4. Calcinate the ruthenium-cobalt-copper metal-organic framework precursor prepared in step S3 to obtain a heterojunction catalyst.

[0007] The principle of the heterojunction catalyst composed of cobalt- and copper-codoped ruthenium dioxide and metallic ruthenium provided by the present invention is as follows: Through hydrothermal action, cobalt metal ions coordinate with carboxylic acid groups in trimesic acid to form a cobalt-based metal-organic framework, and then a ruthenium-cobalt-copper metal-organic framework precursor is prepared by using the multiple ion exchange method. In the first ion exchange process, since the interaction between copper and the ligand trimesic acid is slightly stronger than that between cobalt and trimesic acid, copper metal ions exchange with some cobalt metal ions in the organic phase solution, thereby forming a cobalt-copper metal-organic framework. In the second ion exchange process, when reacting with the cobalt-copper metal-organic framework precursor, ruthenium ions can compete with the original cobalt and copper ligand coordination bonds by virtue of their strong coordination ability, and thus replace cobalt and copper ions to combine with the ligand to form a ruthenium-cobalt-copper metal-organic framework. Subsequently, in an air atmosphere, part of the ruthenium metal ions are converted into ruthenium metal oxides, most of the cobalt and copper ions are ion-exchanged into the solution, and the remaining cobalt and copper ions are doped into the ruthenium metal oxide lattice during the calcination process, while the remaining metallic ruthenium forms a tight heterojunction interface with ruthenium dioxide in the form of nanoparticles, thus obtaining a heterojunction catalyst composed of cobalt- and copper-codoped ruthenium dioxide and metallic ruthenium.

[0008] Compared with the prior art, the present invention adopts a stepwise ion exchange strategy, preferentially introducing copper ions to partially replace cobalt sites, and then using the stronger coordination ability of ruthenium ions to displace cobalt and copper ions. Finally, during the calcination process, cobalt and copper atoms are uniformly doped into the ruthenium dioxide lattice, while retaining the heterogeneous interface of ruthenium metal nanoparticles.

[0009] In a possible implementation manner, in the step S1, the molar ratio of the cobalt salt to the 1,3,5-benzenetricarboxylic acid is 1:(1 - 10).

[0010] Compared with the prior art, the advantage of the present invention adopting the above molar ratio is that when the content of the cobalt salt is too low, during the hydrothermal process, only a small part of the 1,3,5-benzenetricarboxylic acid can combine with cobalt ions to form cobalt-based metal-organic frameworks, while too much cobalt salt will lead to an excessive amount of cobalt ions in the solution, easily generating cobalt metal hydroxide hydrates, which will affect the subsequent ion exchange process, resulting in ruthenium being unable to exchange cobalt metal ions in the precursor into the solution, and having a great impact on the formation of the final product cobalt-doped ruthenium oxide.

[0011] In a possible implementation manner, the cobalt salt is a soluble salt, and its selection includes nitrates, chlorides, acetates, nitrates and their hydrates, chlorides and their hydrates, acetates and their hydrates, etc., preferably cobalt nitrate, cobalt chloride, cobalt acetate, etc.

[0012] In a possible implementation manner, in the step S1, the mixed solution is composed of deionized water, ethanol and N,N-dimethylformamide, and the mass ratio is 1:1:1.

[0013] Compared with the prior art, the present invention uses a mixed solution of deionized water, ethanol and N,N-dimethylformamide as the reaction solvent. Different selections of solvents during the hydrothermal reaction process will have an obvious impact on the microscopic morphology of the product. In order to obtain the target nanoparticle structure, a mixed solution of deionized water, ethanol and N,N-dimethylformamide is selected as the reaction solvent.

[0014] In a possible implementation manner, in the step S1, the hydrothermal reaction is carried out in a high-pressure hydrothermal reaction kettle, and the parameters of the hydrothermal reaction are as follows: the temperature is 120 - 180 °C, and the time is 10 - 25 h.

[0015] Compared with the prior art, the present invention carries out the hydrothermal reaction by adopting the above parameters because adopting a relatively moderate temperature and an appropriate reaction time (120 - 180 °C and 10 - 25 h respectively in the present invention) is beneficial to ensuring the uniformity of the morphology structure of the cobalt-based metal-organic framework.

[0016] In a possible implementation manner, in the step S2, the molar ratio of the copper salt to the 1,3,5-benzenetricarboxylic acid in the methanol solution is 1:(1 - 10), and the mass ratio of the copper salt to the cobalt-based metal-organic framework precursor is 1:(1 - 10).

[0017] Compared with the prior art, the present invention uses the copper salt with the above-mentioned concentration and mass ratio because: when the concentration of the copper metal salt is too high and the content is too much, most of the cobalt metal ions will be exchanged by the copper metal ions, which is not conducive to the subsequent secondary exchange of ruthenium metal ions and cobalt and copper metal ions. If the concentration of the 1,3,5-benzenetricarboxylic acid is too low and the content is too little, it will not be conducive to the 1,3,5-benzenetricarboxylic acid to combine with cobalt and copper ions to form cobalt and copper metal-organic frameworks.

[0018] In a possible implementation manner, the copper salt is a soluble salt, and its selection includes nitrates, chlorides, acetates, and their hydrates, etc., such as copper nitrate, copper chloride, etc.

[0019] In a possible implementation manner, in the step S3, in the aqueous solution containing the ruthenium salt, the concentration of the ruthenium salt is 10-20 mg / ml.

[0020] In a possible implementation manner, in the step S3, the mass ratio of the ruthenium salt to the cobalt-copper metal-organic framework precursor is 1:(1-10).

[0021] The present invention uses the ruthenium salt with the above-mentioned concentration and mass ratio because: when the concentration of the ruthenium metal salt is too high and the content is too much, most of the cobalt and copper metal ions will be exchanged by the ruthenium metal ions, and the cobalt-copper doping effect is not obvious. When the concentration of the ruthenium metal salt is too low and the content is too little, it will affect the effect of the cobalt and copper metal ions being exchanged by the ruthenium metal ions, resulting in too low ruthenium content in the final product and a decrease in catalytic activity.

[0022] In a possible implementation manner, the ruthenium salt includes chlorides, ruthenates and their hydrates, etc., such as ruthenium chloride, potassium ruthenate, ammonium chlororuthenate, etc.

[0023] In a possible implementation manner, the parameters of the heating and stirring are as follows: the temperature is 50-70 °C, and the time is 4-12 h.

[0024] Compared with the prior art, the present invention uses the above parameters for heating and stirring treatment because: by controlling the temperature and time of the ion exchange reaction, it is conducive to the controllable exchange of ruthenium metal ions and cobalt and copper ions. Specifically, when the temperature is too low and the reaction time is short, the exchange effect of ruthenium metal ions and cobalt and copper metal ions is poor, and the ruthenium content in the formed ruthenium-cobalt-copper metal-organic framework is low. When the temperature is too high and the reaction time is too long, it may cause the solvent to volatilize violently, resulting in a sudden change in the concentration of the reaction system and affecting the uniformity of the bimetallic doping.

[0025] In a possible implementation manner, in the step S4, the calcination treatment is carried out in a tube furnace, and the parameters of the calcination treatment are as follows: the temperature is 200-500 °C, the heating rate is 1-5 °C / min, and the atmosphere is air.

[0026] Compared with the prior art, the present invention uses the above parameters for calcination treatment because: under such conditions, the morphology and crystal structure of ruthenium metal oxide nanoparticles are well maintained, and the performance of the obtained catalyst is the most excellent.

[0027] The second object of the present invention is to provide a heterojunction catalyst composed of cobalt and copper co-doped ruthenium dioxide and metallic ruthenium, which is prepared by the above preparation method.

[0028] The heterojunction catalyst composed of cobalt and copper co-doped ruthenium dioxide and metallic ruthenium prepared by the present invention can be represented by the chemical formula: Co,Cu-RuO2@Ru, where Co,Cu- represents cobalt and copper doping; RuO2@Ru is a heterostructure composed of ruthenium metal oxide and metallic ruthenium; in the ruthenium oxide nanoparticle electrocatalyst prepared by the present invention, there is an interaction between ruthenium and ruthenium oxide, which can coordinate the electron transfer in the reaction process, accelerate the generation and transformation of oxygen intermediates, and at the same time, cobalt and copper doping can further accelerate the electron transfer between metal sites, enabling the ruthenium active sites to be in a highly active state for a long time.

[0029] The third object of the present invention is to provide an application of a heterojunction catalyst composed of cobalt and copper co-doped ruthenium dioxide and metallic ruthenium as a working electrode in the anodic oxygen evolution reaction of water electrolysis in an acidic solution.

[0030] Specifically, the above application is as follows: in the anodic oxygen evolution reaction of acidic water electrolysis, a three-electrode system is adopted. Specifically, a Hg / Hg2SO4 electrode is used as the reference electrode, a carbon rod is used as the counter electrode, a carbon paper coated with the heterostructure composed of metallic ruthenium provided by the present invention is used as the working electrode, and a 0.5 M sulfuric acid solution is used as the electrolyte.

[0031] The heterostructure composed of cobalt and copper co-doped ruthenium oxide and metallic ruthenium provided by the present invention is composed of two parts: cobalt and copper co-doped ruthenium oxide and metallic ruthenium. There is an interaction of the heterostructure between ruthenium oxide and ruthenium, which enables the electrode material to exhibit good electron transfer properties and is also beneficial to the stability of the overall structure during the reaction process. At the same time, cobalt and copper are doped into ruthenium metal oxide, which is beneficial to further accelerating the electron transfer to improve the overall catalytic activity of the material.

[0032] Compared with the prior art, the present invention has the following beneficial effects: (1) The heterostructure composed of cobalt and copper co-doped ruthenium oxide and metallic ruthenium provided by the present invention exhibits high oxygen evolution electrocatalytic activity and good stability in the acidic water electrolysis reaction. When the current density is 10 mA cm -2 , the anodic reaction overpotential is only about 199 mV, and it can maintain for 40 h without obvious potential change, which further promotes the technical development of PEM water electrolysis for hydrogen production;

[0033] (2) The heterostructure composed of ruthenium oxide and metallic ruthenium provided by the present invention optimizes the electronic environment of ruthenium sites by coupling metallic ruthenium and cobalt-copper co-doped ruthenium oxide, improving the catalytic activity while ensuring the relative stability of the site valence states. (3) For the cobalt-copper co-doped ruthenium metal oxide and ruthenium nanoparticle heterojunction electrocatalyst provided by the present invention, by controlling the proportion of cobalt and copper doping, the adsorption of water molecules and oxygen-containing intermediates by active sites can be optimized, which is beneficial to the subsequent oxygen evolution reaction in electrolytic water. Description of the Drawings

[0034] Figure 1 SEM image of the catalyst Co,Cu-RuO2@Ru prepared in Example 1 of the present invention; Figure 2 TEM image of the catalyst Co,Cu-RuO2@Ru prepared in Example 1 of the present invention; Figure 3 XRD pattern of the catalyst prepared in Example 1 of the present invention; Figure 4 Polarization curve of the catalysts prepared in Example 1 and Comparative Examples 1-2 of the present invention and commercial RuO2 in the oxygen evolution reaction of acidic electrolytic water in the application example; Figure 5 Curve of voltage vs. time under constant current of the catalyst Co,Cu-RuO2@Ru prepared in Example 1 of the present invention in the oxygen evolution reaction of acidic electrolytic water. Detailed Embodiments

[0035] To make the above objects, features, and advantages of the present invention more obvious and understandable, the following detailed description of the specific embodiments of the present invention will be given with reference to the accompanying drawings.

[0036] It should be understood that the terms described in the present invention are only for describing specific embodiments and are not used to limit the present invention. Additionally, for the numerical ranges in the present invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Each intermediate value within any stated value or stated range, as well as each smaller range between any other stated value or intermediate value within the stated range, is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded from the range.

[0037] Without departing from the scope or spirit of the present invention, various improvements and changes can be made to the specific embodiments of the present invention specification, which are obvious to those skilled in the art. Other embodiments obtained from the specification of the present invention are obvious to those skilled in the art. The specification and embodiments of this application are only exemplary.

[0038] The present application will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0039] Example 1 This example provides a heterojunction catalyst composed of cobalt and copper co-doped ruthenium dioxide and metallic ruthenium, which is prepared by the following method: S1. Weigh 1.2 g of cobalt nitrate hexahydrate and 0.5 g of 1,3,5-benzenetricarboxylic acid. Mix and dissolve them in 60 mL of a mixed solution of deionized water, ethanol, and N,N-dimethylformamide with a volume ratio of (1:1:1). Then, put the prepared solution into an ultrasonic cleaner and ultrasonicate for 20 min, and then stir for 30 min to make it evenly mixed. S2. Transfer the mixed solution to a 100 mL high-pressure reaction kettle, put the high-pressure reaction kettle into an electrothermal constant-temperature forced-air drying oven, set the temperature to 150 °C and the reaction time to 24 h. When the temperature drops to room temperature, take out the high-pressure reaction kettle and centrifuge and wash it three times with ethanol and deionized water respectively to obtain a cobalt-based metal-organic framework. S3. Weigh 100 mg of the prepared cobalt-based metal-organic framework and dissolve it in 30 mL of methanol solution. Then add 10 mg of copper nitrate hexahydrate and 43 mg of 1,3,5-benzenetricarboxylic acid. Stir at room temperature for 4 h and then centrifuge to obtain a cobalt-copper metal-organic framework. S4. Dissolve the prepared 100 mg of cobalt-copper metal-organic framework in water again, heat and stir at 60 °C, and at the same time, dropwise add 4 mL of a 10 mg / mL -1 aqueous solution of ruthenium chloride. After reacting for 8 h, centrifuge to obtain a ruthenium-cobalt-copper metal-organic framework. S5. Weigh 100 mg of the prepared ruthenium-cobalt-copper metal-organic framework powder and place it in a muffle furnace. Under an air atmosphere, heat it at a rate of 2 o °C / min -1 to 350 o °C and keep it warm for 4 h. After the reaction is completed, cool it to room temperature to obtain a cobalt- and copper-doped ruthenium metal oxide nanoparticle electrocatalyst, denoted as Co,Cu-RuO2@Ru.

[0040] The catalyst prepared in this example was observed for its microscopic morphology by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The SEM results are as Figure 1 shown, and the TEM image is as Figure 2 shown. It can be seen from Figure 1-2 that the cobalt- and copper-doped ruthenium metal oxide nanoparticle electrocatalyst maintains a granular structure. The X-ray diffraction (XRD) pattern of the cobalt- and copper-doped ruthenium metal oxide nanoparticle electrocatalyst prepared in this example is as Figure 3 shown. It can be seen from Figure 3It can be seen that the characteristic peaks of ruthenium oxide and ruthenium shown in the catalyst, while the characteristic peaks of copper oxide and cobalt oxide do not appear, proving the successful synthesis of the heterojunction catalyst composed of cobalt and copper co-doped ruthenium dioxide and metallic ruthenium.

[0041] Example 2 This example provides a heterojunction catalyst composed of cobalt and copper co-doped ruthenium dioxide and metallic ruthenium, which is prepared by the following method: S1. Weigh 1.2 g of cobalt nitrate hexahydrate and 0.5 g of 1,3,5-benzenetricarboxylic acid, and dissolve them in 60 mL of deionized water, ethanol and N,N-dimethylformamide with a volume ratio of (1:1:1). Then put the prepared solution into an ultrasonic cleaner and ultrasonicate for 20 min, and then stir for 30 min to make it mix evenly. S2. Transfer the mixed solution to a 100 mL autoclave, put the autoclave into an electrothermal constant temperature forced air drying oven, set the temperature to 120 °C and the reaction time to 16 h. When the temperature drops to room temperature, take out the autoclave and centrifuge and wash it three times with ethanol and deionized water respectively to obtain cobalt-based metal-organic framework. S3. Weigh 100 mg of the prepared cobalt-based metal-organic framework and dissolve it in 30 mL of methanol solution, then add 10 mg of copper nitrate hexahydrate and 43 mg of 1,3,5-benzenetricarboxylic acid, and stir at room temperature for 4 h and then centrifuge to obtain cobalt and copper metal-organic framework. S4. Dissolve the prepared 100 mg of cobalt and copper metal-organic framework in water again, heat and stir at 60 °C, and at the same time add 4 mL of 10 mg / mL -1 aqueous solution of ruthenium chloride, and centrifuge after reacting for 8 h to obtain ruthenium-cobalt-copper metal-organic framework. S5. Weigh 100 mg of the prepared ruthenium-cobalt-copper metal-organic framework powder and place it in a muffle furnace. Under an air atmosphere, heat it at 1 o °C / min -1 to 200 o °C and keep it warm for 4 h; after the reaction is completed, cool it to room temperature to obtain the heterojunction catalyst composed of cobalt and copper co-doped ruthenium dioxide and metallic ruthenium, denoted as Co,Cu-RuO2@Ru.

[0042] Example 3 This example provides a heterojunction catalyst composed of cobalt and copper co-doped ruthenium dioxide and metallic ruthenium, which is prepared by the following method: S1. Weigh 1.2 g of cobalt nitrate hexahydrate and 0.5 g of 1,3,5-benzenetricarboxylic acid, and dissolve them in 60 mL of deionized water, ethanol and N,N-dimethylformamide with a volume ratio of (1:1:1). Then put the prepared solution into an ultrasonic cleaner and ultrasonicate for 20 min, and then stir for 30 min to make it mix evenly. S2. Transfer the mixed solution into a 100 mL high-pressure reactor, place the high-pressure reactor in an electrothermal constant-temperature forced-air drying oven, set the temperature to 130 °C and the reaction time to 18 h. Take out the high-pressure reactor when the temperature drops to room temperature, and centrifuge and wash it three times with ethanol and deionized water respectively to obtain cobalt-based metal-organic framework; S3. Weigh 100 mg of the prepared cobalt-based metal-organic framework and dissolve it in 30 mL of methanol solution, then add 10 mg of copper nitrate hexahydrate and 43 mg of 1,3,5-benzenetricarboxylic acid. After stirring at room temperature for 4 h, centrifuge to obtain cobalt-copper metal-organic framework; S4. Dissolve 100 mg of the prepared cobalt-copper metal-organic framework in water again, heat and stir at 60 °C, and at the same time add 4 mL of 10 mg / mL -1 aqueous solution of ruthenium chloride. After reacting for 8 h, centrifuge to obtain ruthenium-cobalt-copper metal-organic framework; S5. Weigh 100 mg of the prepared ruthenium-cobalt-copper metal-organic framework powder and place it in a muffle furnace. Under an air atmosphere, heat it at 3 o °C / min -1 to 300 o °C and keep it warm for 4 h; after the reaction is completed, cool it to room temperature to obtain a heterojunction catalyst composed of cobalt- and copper-codoped ruthenium dioxide and metallic ruthenium, denoted as Co,Cu-RuO2@Ru.

[0043] Example 4 This example provides a heterojunction catalyst composed of cobalt- and copper-codoped ruthenium dioxide and metallic ruthenium, which is prepared by the following method: S1. Weigh 1.2 g of cobalt nitrate hexahydrate and 0.5 g of 1,3,5-benzenetricarboxylic acid, dissolve them in 60 mL of a mixed solution of deionized water, ethanol and N,N-dimethylformamide with a volume ratio of (1:1:1). Then put the prepared solution into an ultrasonic cleaner and ultrasonicate for 20 min, and then stir for 30 min to make it evenly mixed; S2. Transfer the mixed solution into a 100 mL high-pressure reactor, place the high-pressure reactor in an electrothermal constant-temperature forced-air drying oven, set the temperature to 140 °C and the reaction time to 20 h. Take out the high-pressure reactor when the temperature drops to room temperature, and centrifuge and wash it three times with ethanol and deionized water respectively to obtain cobalt-based metal-organic framework; S3. Weigh 100 mg of the prepared cobalt-based metal-organic framework and dissolve it in 30 mL of methanol solution, then add 10 mg of copper nitrate hexahydrate and 43 mg of 1,3,5-benzenetricarboxylic acid. After stirring at room temperature for 4 h, centrifuge to obtain cobalt-copper metal-organic framework; S4. Redissolve the prepared 100 mg of cobalt-copper metal-organic framework in water, heat and stir at 60 °C, and simultaneously add 4 mL of an aqueous ruthenium chloride solution with a concentration of 10 mg / mL dropwise to the solution. After reacting for 8 h, centrifuge to obtain a ruthenium-cobalt-copper metal-organic framework; -1 S5. Weigh 100 mg of the prepared ruthenium-cobalt-copper metal-organic framework powder and place it in a muffle furnace. Under an air atmosphere, heat it at a rate of 4 C / min o to 400 -1 °C and keep it at this temperature for 4 h; after the reaction is completed, cool it to room temperature to obtain a heterojunction catalyst composed of cobalt-copper co-doped ruthenium dioxide and metallic ruthenium, denoted as Co,Cu-RuO2@Ru. o Example 5

[0044] This example provides a heterojunction catalyst composed of cobalt-copper co-doped ruthenium dioxide and metallic ruthenium, which is prepared by the following method: S1. Weigh 1.2 g of cobalt nitrate hexahydrate and 0.5 g of 1,3,5-benzenetricarboxylic acid. Mix and dissolve them in 60 mL of a mixed solution of deionized water, ethanol, and N,N-dimethylformamide with a volume ratio of (1:1:1). Then, put the prepared solution into an ultrasonic cleaner and ultrasonicate for 20 min, and then stir for 30 min to make it evenly mixed; S2. Transfer the mixed solution to a 100 mL autoclave, place the autoclave in an electrothermal constant-temperature forced-air drying oven, set the temperature to 160 °C and the reaction time to 22 h. When the temperature drops to room temperature, take out the autoclave and centrifuge and wash it three times with ethanol and deionized water respectively to obtain a cobalt-based metal-organic framework; S3. Weigh 100 mg of the prepared cobalt-based metal-organic framework and dissolve it in 30 mL of methanol solution. Then add 10 mg of copper nitrate hexahydrate and 43 mg of 1,3,5-benzenetricarboxylic acid, and stir at room temperature for 4 h and then centrifuge to obtain a cobalt-copper metal-organic framework; S4. Redissolve the prepared 100 mg of cobalt-copper metal-organic framework in water, heat and stir at 60 °C, and simultaneously add 4 mL of an aqueous ruthenium chloride solution with a concentration of 10 mg / mL dropwise to the solution. After reacting for 8 h, centrifuge to obtain a ruthenium-cobalt-copper metal-organic framework; S5. Weigh 100 mg of the prepared ruthenium-cobalt-copper metal-organic framework powder and place it in a muffle furnace. Under an air atmosphere, heat it at a rate of 5 -1 C / min to 500 o °C and keep it at this temperature for 4 h; after the reaction is completed, cool it to room temperature to obtain a heterojunction catalyst composed of cobalt-copper co-doped ruthenium dioxide and metallic ruthenium, denoted as Co,Cu-RuO2@Ru. -1 °C and keep it at this temperature for 4 h; after the reaction is completed, cool it to room temperature to obtain a heterojunction catalyst composed of cobalt-copper co-doped ruthenium dioxide and metallic ruthenium, denoted as Co,Cu-RuO2@Ru. o ​

[0045] Comparative Example 1 This comparative example provides a heterogeneous structure catalyst composed of cobalt-doped ruthenium dioxide and metallic ruthenium. The difference from Example 1 is only that step S3 is not carried out in the preparation process of this comparative example. The specific steps are as follows: S1. Weigh 1.2 g of cobalt nitrate hexahydrate and 0.5 g of 1,3,5-benzenetricarboxylic acid, and dissolve them in 60 mL of a mixed solution of deionized water, ethanol, and N,N-dimethylformamide with a volume ratio of (1:1:1). Then put the prepared solution into an ultrasonic cleaner and ultrasonicate for 20 min, and then stir for 30 min to make it evenly mixed; S2. Transfer the mixed solution to a 100 mL high-pressure reaction kettle, put the high-pressure reaction kettle into an electrothermal constant-temperature forced-air drying oven, set the temperature to 150 °C and the reaction time to 24 h. When the temperature drops to room temperature, take out the high-pressure reaction kettle and centrifuge and wash it three times with ethanol and deionized water respectively to obtain a cobalt-based metal-organic framework; S3. Dissolve 100 mg of the prepared cobalt-based metal-organic framework in water, heat and stir at 60 °C, and at the same time add 4 mL of a 10 mg / mL -1 ruthenium chloride aqueous solution. After reacting for 8 h, centrifuge to obtain a ruthenium-cobalt metal-organic framework; S4. Weigh 100 mg of the prepared ruthenium-cobalt metal-organic framework powder and place it in a muffle furnace. Under an air atmosphere, heat it at a rate of 2 o °C / min -1 to 350 o °C and keep it at this temperature for 4 h. After the reaction is completed, cool it to room temperature to obtain a heterogeneous structure catalyst composed of cobalt-doped ruthenium dioxide and metallic ruthenium, denoted as Co-RuO2@Ru.

[0046] Comparative Example 2 This comparative example provides a heterogeneous structure catalyst composed of copper-doped ruthenium dioxide and metallic ruthenium. The difference from Example 1 is only that cobalt nitrate added in step S1 of this comparative example is replaced by copper nitrate, and step S3 is not carried out. The specific steps are as follows: S1. Weigh 1 g of copper nitrate hexahydrate and 0.43 g of 1,3,5-benzenetricarboxylic acid, and dissolve them in 60 mL of a mixed solution of deionized water, ethanol, and N,N-dimethylformamide with a volume ratio of (1:1:1). Then put the prepared solution into an ultrasonic cleaner and ultrasonicate for 20 min, and then stir for 30 min to make it evenly mixed; S2. Transfer the mixed solution to a 100 mL high-pressure reaction kettle, put the high-pressure reaction kettle into an electrothermal constant-temperature forced-air drying oven, set the temperature to 150 °C and the reaction time to 24 h. When the temperature drops to room temperature, take out the high-pressure reaction kettle and centrifuge and wash it three times with ethanol and deionized water respectively to obtain a copper-based metal-organic framework; S3. Redissolve the prepared 100 mg of copper metal-organic framework in water, heat and stir at 60 °C, and simultaneously dropwise add 4 mL of an aqueous solution of ruthenium chloride with a concentration of 10 mg / mL -1 to the solution. After reacting for 8 h, centrifuge to obtain a ruthenium-copper metal-organic framework; S4. Weigh 100 mg of the prepared ruthenium-copper metal-organic framework powder and place it in a muffle furnace. Under an air atmosphere, heat it at a rate of 2 o °C / min -1 to 350 o °C and keep it at this temperature for 4 h. After the reaction is completed, cool it to room temperature to obtain a heterostructure catalyst composed of copper-doped ruthenium dioxide and metallic ruthenium, denoted as Cu-RuO2@Ru.

[0047] Application Example (1) Using a three-electrode system, use the heterojunction catalyst composed of cobalt-copper co-doped ruthenium dioxide and metallic ruthenium prepared in Example 1, the heterostructure catalyst composed of cobalt-doped ruthenium dioxide and metallic ruthenium prepared in Comparative Example 1, the heterostructure catalyst composed of copper-doped ruthenium dioxide and metallic ruthenium prepared in Comparative Example 2, and commercially available RuO2-coated carbon paper as the working electrode, a carbon rod as the counter electrode, and a saturated Hg / Hg2SO4 electrode as the reference electrode. The electrolyte is 0.5 M H2SO4; (2) CV activation: Use a Shanghai Chenhua CHI 760E electrochemical workstation. Before testing, purge argon into the electrolyte for 30 min. Adopt the CV program, the test range is 0.8 - 1.5 V vs. RHE, and the scan rate is 50 mV / s -1 , and cycle 40 times until the electrode reaches a stable state.

[0048] Perform linear sweep voltammetry (LSV) tests on the heterojunction catalyst composed of cobalt-copper co-doped ruthenium dioxide and metallic ruthenium prepared in Example 1, the heterostructure catalyst composed of cobalt-doped ruthenium dioxide and metallic ruthenium prepared in Comparative Example 1, the heterostructure catalyst composed of copper-doped ruthenium dioxide and metallic ruthenium prepared in Comparative Example 2, and commercially available RuO2 After activation, switch the program to the LSV program. The test range is 0.8 - 1.5 V vs. RHE, and the scan rate is 5 mV / s -1 , and the overpotential is the difference between the potential measured at 1.23 V versus the reversible hydrogen electrode and the potential measured at 10 mA / cm -2 . As Figure 4 shown, the polarization curves of the Co,Cu-RuO2@Ru, Co-RuO2@Ru, Cu-RuO2@Ru, and RuO2 provided in this example for the oxygen evolution reaction of water electrolysis in a 0.5 M H2SO4 solution are as shown in Figure 4 shown. From Figure 4It can be seen that in the acidic oxygen evolution reaction, the overpotential of the Co,Cu-RuO2@Ru catalyst is only 199 mV, which is significantly better than that of Co-RuO2@Ru, Cu-RuO2@Ru and commercial RuO2.

[0049] The stability test was carried out on the heterojunction catalyst composed of cobalt-copper co-doped ruthenium dioxide and ruthenium metal prepared in Example 1: After CV activation, the switching program was the ISTEP program, the current was set to 0.7 mA, and the time was set to 40 h. As Figure 5 shown, the potential of the heterojunction catalyst composed of cobalt-copper co-doped ruthenium dioxide and ruthenium metal basically did not change, proving its good oxygen evolution stability.

[0050] From the above results, it can be seen that for the heterojunction catalyst composed of cobalt-copper co-doped ruthenium dioxide and ruthenium metal provided by the present invention, by controlling the proportion of cobalt-copper doping, the adsorption of active sites on water molecules and oxygen-containing intermediates can be optimized, which is beneficial to the subsequent electrolytic water oxygen evolution reaction.

[0051] The above is only the specific implementation manner of this application, but the protection scope of this application is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed in this application should be covered by the protection scope of this application. Therefore, the protection scope of this application should be subject to the protection scope of the claims.

Claims

1. A preparation method of a heterojunction catalyst composed of cobalt and copper co-doped ruthenium dioxide and metallic ruthenium, characterized in that, The preparation method specifically includes the following steps: S1. Dissolve cobalt salt and trimesic acid in a mixed solution. After stirring and mixing evenly, obtain a cobalt metal-organic framework precursor through a hydrothermal reaction; S2. Dissolve the cobalt metal-organic framework precursor prepared in step S1 in a methanol solution. While stirring at room temperature, dropwise add a methanol solution containing copper salt and trimesic acid. After mixing evenly, obtain a cobalt-copper metal-organic framework precursor; S3. Dissolve the cobalt-copper metal-organic framework precursor prepared in step S2 in an aqueous solution. While heating and stirring, dropwise add an aqueous solution containing ruthenium salt to carry out an ion exchange reaction to obtain a ruthenium-cobalt-copper metal-organic framework precursor; S4. Calcinate the ruthenium-cobalt-copper metal-organic framework precursor prepared in step S3 to obtain a heterojunction catalyst.

2. The preparation method according to claim 1, characterized in that, In step S1, the molar ratio of cobalt salt to trimesic acid is 1:(1 - 10).

3. The preparation method according to claim 1, characterized in that, In step S1, the mixed solution is composed of deionized water, ethanol, and N,N-dimethylformamide, and the volume ratio is 1:1:

1.

4. The preparation method according to claim 1, characterized in that In step S1, the hydrothermal reaction is carried out in a high-pressure hydrothermal reaction kettle, and the parameters of the hydrothermal reaction are as follows: the temperature is 120 - 180 °C, and the time is 10 - 25 h.

5. The preparation method according to claim 1, characterized in that, In step S2, the molar ratio of copper salt to trimesic acid in the methanol solution is 1:(1 - 10), and the mass ratio of copper salt to the cobalt metal-organic framework precursor is 1:(1 - 10).

6. The preparation method according to claim 1, characterized in that, In step S3, in the aqueous solution containing ruthenium salt, the concentration of ruthenium salt is 10 - 20 mg / ml.

7. The preparation method according to claim 1, wherein In step S3, the mass ratio of ruthenium salt to the cobalt-copper metal-organic framework precursor is 1:(1 - 10); and / or, the parameters of heating and stirring are as follows: the temperature is 50 - 70 °C, and the time is 4 - 12 h.

8. The preparation method according to claim 1, characterized in that, In step S4, the calcination treatment is carried out in a tubular furnace, and the parameters of the calcination treatment are as follows: the temperature is 200 - 500 °C, the heating rate is 1 - 5 °C / min, and the atmosphere is air.

9. A heterojunction catalyst composed of cobalt and copper co-doped ruthenium dioxide and metallic ruthenium, characterized in that, Prepared by the preparation method according to any one of claims 1 - 8.

10. Application of a heterojunction catalyst composed of cobalt-copper co-doped ruthenium dioxide and metallic ruthenium as described in claim 9 as a working electrode in the anodic oxygen evolution reaction of water electrolysis in an acidic solution.

Images