Method for preparing rare earth-manganese oxide coating anode through electro-deposition

Abstract

The invention provides a method for preparing a rare earth-manganese oxide coating anode through electro-deposition, manganese ions in electro-deposition liquid are oxidized in a pulse deposition mode, so that the manganese ions and rare earth ions are deposited on the surface of a metal matrix with a stable size in a composite oxide form, and the rare earth-manganese oxide coating anode is formed. The rare earth-manganese oxide coating anode prepared through the method is high in stability, grains can be refined, the electrocatalytic activity can be enhanced, the current density can be improved, and energy consumption can be reduced. Meanwhile, the preparation method is easy to operate, low in cost and capable of being applied to the field of industrial electrolysis on a large scale.

Description

Technical Field

[0001] The present application relates to the technical fields of hydrometallurgy, water electrolysis and electrolysis of various organic and inorganic substances, and in particular to a method for preparing a rare earth-manganese oxide coated anode by electrodeposition. Background Art

[0002] Dimensionally stable anode (DSA) is a new type of insoluble anode, which is widely used in metallurgy, water treatment, environmental protection, electroplating, electrolysis of water to produce hydrogen and other fields. DSA anode uses insoluble metals with good conductivity as the substrate (such as Ti, Pb-Ag, etc.), and is coated with metal oxides on the surface. It has good electrocatalytic activity, conductivity, oxidation resistance and corrosion resistance. These characteristics make DSA anodes perform well in various electrolysis and electrochemical processes, and can effectively reduce overpotential, save electricity and extend service life. At present, in long-cycle industrial production processes, the more mature and effective coatings are oxide coatings of precious metals such as Ru and Ir. However, the high price of precious metals limits their large-scale use in industry.

[0003] In recent years, a lot of research has been done on non-precious metal DSA anode coating materials. Among them, manganese-based oxides have a stable potential window under acidic OER conditions, which makes manganese-based oxides have the potential to continue oxygen evolution reaction for a long time. However, in strong acid and long-term use, manganese is extremely easy to oxidize to a higher valence state of MnO 4- , which causes the catalyst to dissolve and deactivate. Summary of the invention

[0004] To solve the above problems, the present invention provides a method for preparing a rare earth-manganese oxide coated anode by electrodeposition, combining rare earth elements with manganese elements, solving the problem that manganese-based oxides are easily deactivated in a strong acid environment, and significantly improving the electrocatalytic performance, stability and service life of the anode. In addition, the method is low in cost, strong in adaptability, and has significant economic and environmental benefits, providing reliable technical support for the wide application of DSA anodes in metallurgy, water treatment, electrolysis of water to produce hydrogen and other fields.

[0005] In a first aspect, the present invention provides a method for preparing a rare earth-manganese oxide coated anode by electrodeposition, the method comprising: Taking appropriate amounts of rare earth element-containing compounds and manganese element-containing compounds and adding them into an acid solution to prepare an electrodeposition solution; wherein the rare earth element is a lanthanide element; Using the pretreated metal substrate as an anode and the platinum electrode as a cathode, pulse deposition is performed in the electrodeposition solution to form a rare earth-manganese oxide coating on the surface of the metal substrate through an oxidation reaction, thereby obtaining the rare earth-manganese oxide coating anode; In the electrodeposition solution, the concentration of the acid solution is 20 g / L-50 g / L, the concentration of the manganese element is 10 g / L-40 g / L, and the concentration of the rare earth element is 0.1%-20% of the concentration of the manganese element.

[0006] Furthermore, the current density of the pulse deposition is 0.2 mA / cm 2 ~10 mA / cm 2 , deposition time is 30 min~300 min, working ratio is 5%~50%, frequency is 5 Hz~15 Hz, and temperature is 25 ℃~100 ℃.

[0007] Furthermore, the rare earth element is at least one of La, Ce, Pr, Nd, Sm and Er.

[0008] Furthermore, the manganese-containing compound is at least one of manganese sulfate, manganese nitrate, manganese chloride and manganese acetate.

[0009] Furthermore, the preprocessing includes: The polished metal substrate is placed in a sodium hydroxide solution and heated for degreasing treatment; The metal substrate after degreasing treatment is placed in an oxalic acid solution and acid-etched at 90°C to 110°C for 1 h to 3 h to obtain a metal substrate with a pockmarked surface; The metal matrix is ​​any one of a Ti anode, a Pb-Ag anode and a conductive glass.

[0010] Furthermore, the mass fraction of the sodium hydroxide solution is 5% to 20%; The mass fraction of the oxalic acid solution is 5% to 20%.

[0011] Furthermore, the acid solution is at least one of sulfuric acid, nitric acid, hydrochloric acid and acetic acid.

[0012] Furthermore, the method further comprises: The rare earth-manganese oxide coated anode is placed in a muffle furnace and annealed and calcined at 150° C. to 300° C. for 20 min to 120 min.

[0013] In a second aspect, the present invention provides a rare earth-manganese oxide coated anode, wherein the rare earth-manganese oxide coated anode is prepared by the method described in the first aspect.

[0014] Furthermore, in the rare earth-manganese oxide coated anode, the atomic percentage of rare earth element and manganese element is 0.1%-20%.

[0015] Beneficial technical effects: The present invention provides a method for preparing a rare earth-manganese oxide coating anode by electrodeposition. Rare earth elements (such as lanthanide elements) have unique electronic structures and chemical properties and can form a stable composite oxide coating with manganese elements. Through pulse electrodeposition, the rare earth-manganese oxide coating can be uniformly deposited on the surface of the metal substrate to form a dense and stable structure, which can not only improve the mechanical strength of the coating, but also enhance its corrosion resistance in a strong acid environment.

[0016] The addition of rare earth elements can inhibit the oxidation of manganese to high-valent MnO in a strong acid environment. 4- , thereby reducing the dissolution and deactivation of the catalyst and significantly improving the stability of the coating. It also optimizes the electronic structure of the coating and enhances its electrocatalytic activity, thereby reducing the overpotential of the oxygen evolution reaction, allowing the anode to more efficiently perform the oxygen evolution reaction during the electrolysis process and save electrical energy.

[0017] Because the rare earth-manganese oxide coating has excellent oxidation resistance and corrosion resistance, the anode can maintain stable performance during long-term use, reduce the replacement frequency due to coating failure, extend the service life of the anode, and reduce industrial waste generated by frequent replacement of the anode, which meets environmental protection requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the description of the embodiments of the present application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0019] Figure 1 A flow chart of a method for preparing a rare earth-manganese oxide coated anode by electrodeposition proposed in an embodiment of the present application is shown; Figure 2 The rare earth-manganese oxide coating anode prepared in Examples 1 and 2 of the present application is shown in -1 mA / cm 2 Accelerated life test results at current density. DETAILED DESCRIPTION

[0020] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0021] In the drawings, the size of the constituent elements, the thickness of the layer or the area may be exaggerated for the sake of clarity. Therefore, any implementation of the present disclosure is not necessarily limited to the size shown in the drawings, and the shapes and sizes of the components in the drawings do not reflect the true proportions. In addition, the drawings schematically show ideal examples, and any implementation of the present disclosure is not limited to the shapes or values ​​shown in the drawings.

[0022] In the related art, the dimensionally stable anode (DSA) is a new type of anode material with an insoluble metal with good conductivity as the substrate and a metal oxide coating on the surface. Due to its excellent electrocatalytic activity, conductivity, oxidation resistance and corrosion resistance, DSA anodes are widely used in metallurgy, water treatment, environmental protection, electroplating and electrolysis of water to produce hydrogen. In these applications, DSA anodes can significantly reduce the overpotential in the electrolysis process, improve energy efficiency, and extend service life. However, the DSA anode coating materials widely used in industry currently mainly rely on oxides of precious metals (such as Ru and Ir). Although these precious metal coatings have excellent electrocatalytic performance and stability, their high cost severely limits their large-scale application in industry, especially in long-term and high-intensity industrial production.

[0023] In recent years, in order to reduce costs and reduce dependence on precious metals, researchers have begun to explore non-precious metal coating materials. Among them, manganese-based oxides have shown potential as alternative materials because of their stable potential window under acidic oxygen evolution reaction (OER) conditions. Manganese-based oxides can undergo efficient oxygen evolution reactions in acidic environments, and the cost of raw materials is low, making them suitable for large-scale applications. However, manganese-based oxides face a key problem in practical applications: under strong acid and long-term use conditions, manganese elements are easily oxidized to high-valent MnO4-. This process not only leads to the dissolution and deactivation of the manganese-based catalyst, but also significantly reduces the electrocatalytic performance and stability of the anode, thereby limiting its long-term use in actual industrial environments.

[0024] The root of this problem lies in the chemical instability of manganese in a strong acid environment. As the electrolysis process proceeds, manganese changes from a low-valent state (such as Mn 2+ ) are gradually oxidized to high valence states (such as Mn 7+ , namely MnO 4- ), while high-valent manganese compounds are easily soluble in acidic solutions, causing the coating to be gradually destroyed. In addition, the electrocatalytic activity of manganese-based oxides will gradually decrease with the oxidation of manganese, eventually leading to anode failure. Therefore, how to improve the stability of manganese-based oxides in strong acid environments and inhibit excessive oxidation of manganese has become a key challenge in the development of high-performance non-precious metal DSA anodes.

[0025] Therefore, developing a low-cost, high-stability, and non-precious metal DSA anode coating material with excellent electrocatalytic performance has become an important research direction. The present invention introduces rare earth elements and combines them with manganese elements, which is expected to solve the deactivation problem of manganese-based oxides in strong acid environments, while improving the electrocatalytic performance and stability of the coating, providing technical support for the widespread application of DSA anodes.

[0026] Based on the content of the related art, the present invention provides a method for preparing a rare earth-manganese oxide coated anode by electrodeposition, see Figure 1 , the method comprising: Step S1: adding appropriate amounts of rare earth element-containing compounds and manganese element-containing compounds into an acid solution to prepare an electrodeposition solution; wherein the rare earth element is a lanthanide element; Step S2: using the pretreated metal substrate as an anode and the platinum electrode as a cathode, pulse deposition is performed in the electrodeposition solution to form a rare earth-manganese oxide coating on the surface of the metal substrate through an oxidation reaction, thereby obtaining the rare earth-manganese oxide coating anode; In the electrodeposition solution, the concentration of the acid solution is 20 g / L-50 g / L, the concentration of the manganese element is 10 g / L-40 g / L, and the concentration of the rare earth element is 0.1%-20% of the concentration of the manganese element.

[0027] In a specific implementation, the concentration of the acid solution can be 20 g / L, 25 g / L, 30 g / L, 35 g / L, 40 g / L, 45 g / L, and 50 g / L; the concentration of the acid solution will affect the conductivity and deposition rate of the electrodeposition solution, and by limiting the concentration of the acid solution, the stability of the deposition process and the quality of the coating can be ensured; The concentration of manganese element can be 10 g / L, 15 g / L, 20 g / L, 25 g / L, 30 g / L, 35 g / L, 40 g / L; the concentration of manganese element will affect the composition and thickness of the coating. Too high or too low concentration will affect the performance of the coating. By setting the concentration of manganese element, the coating performance can be optimized. The concentration of the rare earth element can be 0.1%, 1%, 5%, 10%, 15%, and 20% of the concentration of the manganese element; the concentration of the rare earth element determines its content in the coating. By setting the rare earth element content, the stability and electrocatalytic performance of the coating can be effectively improved.

[0028] In the present invention, the atomic electronic structure of the lanthanide elements in the rare earth elements is [ XE ]4 f n 5 d m 6 s 2 ( n=1-14, m =0 or 1), where 6 s The two electrons in the orbital and 5 d or 4 f An electron in an orbit is relatively easy to lose, and its variable electronic structure allows rare earth elements to be used as coupling doping elements. Therefore, in the field of acidic oxygen evolution, rare earth oxides can be combined with other metal or metal oxide catalysts as dopants to significantly enhance the catalytic performance of the composite material.

[0029] In the present invention, the rare earth element can form a stable composite oxide with the manganese element, which has higher chemical inertness in a strong acid environment, is not easily oxidized or dissolved, has higher chemical stability in a strong acid environment, and can effectively inhibit the excessive oxidation of the manganese element and prevent it from being converted into MnO which is easily soluble in an acidic solution. 4- The introduction of rare earth elements not only improves the stability of the coating, but also enhances its electrocatalytic activity, which can reduce the overpotential during the electrolysis process and improve energy efficiency.

[0030] In the method provided by the present invention, pulse deposition can achieve uniform deposition of the coating through periodic current changes, avoiding the phenomenon of local over-thickness or over-thinness. Pulse deposition can also accurately control the formation process of the coating, making the rare earth-manganese oxide coating more uniform and dense, and improving the mechanical strength and corrosion resistance of the coating. By controlling the concentration of the acid solution, manganese element and rare earth element in the electrodeposition solution, the composition and structure of the coating can be further regulated to enhance its stability in a strong acid environment. The obtained rare earth-manganese oxide coating can show higher chemical stability in a strong acid environment, effectively inhibit the excessive oxidation of manganese elements, and extend the service life of the anode.

[0031] In some embodiments, the current density of the pulse deposition is 0.2 mA / cm 2 ~10 mA / cm 2 , deposition time is 30 min~300 min, working ratio is 5%~50%, frequency is 5 Hz~15 Hz, and temperature is 25 ℃~100 ℃.

[0032] In a specific implementation, the current density of the pulse deposition can be 0.2 mA / cm 2 , 0.5 mA / cm 2 , 1 mA / cm 2 , 3mA / cm 2 , 6 mA / cm 2 , 8 mA / cm 2 , 10 mA / cm 2 ; Smaller current density can control the growth rate of the coating, avoiding loose coating caused by too high current or incomplete deposition caused by too low current; It should be noted that low current density means less electricity passes per unit time and a slower deposition rate. This slow deposition process is conducive to the full diffusion of rare earth elements and manganese elements in the electrodeposition solution and uniform deposition on the surface of the metal substrate to form a dense and uniform composite oxide coating; Since the reduction potential of rare earth elements (such as lanthanides) is usually high and the reduction potentials of different rare earth elements are different, low current density can provide a milder reduction environment and suitable deposition conditions for both, so that multiple rare earth elements can be gradually deposited in the order of their reduction potentials, avoiding competitive deposition or selective deposition caused by excessive current density, achieving co-deposition of multiple rare earth elements and manganese, and forming a uniform composite oxide coating on the surface of the metal substrate.

[0033] The deposition time can be 30 min, 50 min, 70 min, 90 min, 100 min, 120 min, 150 min, 170 min, 200 min, 220 min, 250 min, 270 min, 300 min. The deposition time will affect the thickness and integrity of the coating. By setting the deposition time, it can be ensured that the coating reaches a sufficient thickness to provide good protection, while avoiding stress accumulation or cracking of the coating caused by too long deposition time. The working ratio can be 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%; the working ratio will affect the density and uniformity of the coating. A lower working ratio can reduce the internal stress of the coating and improve the mechanical strength and corrosion resistance of the coating. The frequency can be 5 Hz, 6 Hz, 7 Hz, 8 Hz, 9 Hz, 10 Hz, 11 Hz, 12 Hz, 13 Hz, 14 Hz, and 15 Hz. The pulse frequency affects the microstructure and surface morphology of the coating. The appropriate frequency can promote the uniform growth of the rare earth-manganese oxide coating and form a nanostructure with a high specific surface area, thereby enhancing the electrocatalytic activity, reducing the overpotential in the electrolysis process, and improving the energy efficiency. The temperature can be 25 ℃, 30 ℃, 35 ℃, 40 ℃, 45 ℃, 50 ℃, 55 ℃, 60 ℃, 65 ℃, 70 ℃, 75 ℃, 80 ℃, 85 ℃, 90 ℃, 95 ℃, 100 ℃; the deposition temperature will affect the reaction kinetics of the electrodeposition solution and the crystallinity of the coating. At higher temperatures, the crystallinity of the coating will increase, and the conductivity and electrocatalytic activity will be enhanced; at the same time, temperature control can also avoid coating defects or thermal damage to the substrate material caused by excessively high temperature.

[0034] In the present invention, by controlling the current density, deposition time, working ratio, frequency and temperature, a uniform, dense and chemically stable rare earth-manganese oxide coating can be formed on the surface of the metal substrate. This coating can effectively inhibit the oxidation of manganese in a strong acid environment and prevent it from being converted into MnO which is easily soluble in acidic solutions. 4- . The use of pulse deposition to prepare coatings can reduce pores and cracks in the coatings by utilizing periodic current changes, improve the mechanical strength and corrosion resistance of the coatings, and further enhance the stability of the coatings in long-term, high-intensity industrial environments. Combined with the set deposition time and working ratio, the production cycle can be shortened, production efficiency can be improved, and production costs can be further reduced, making it suitable for large-scale industrial applications.

[0035] In some embodiments, the rare earth element is at least one of La, Ce, Pr, Nd, Sm and Er.

[0036] It should be noted that La (lanthanum) can improve the chemical stability and electrocatalytic activity of the coating, and enhance the density and adhesion of the coating; Ce (cerium) has excellent redox properties, can inhibit the dissolution of manganese, and improve the mechanical strength and corrosion resistance of the coating; Pr (praseodymium) can optimize the electronic structure of the coating, improve the electrocatalytic activity, and enhance the conductivity and stability of the coating; Nd (neodymium) can improve the oxygen evolution reaction activity of the coating and enhance the adhesion between the coating and the substrate; Sm (Samarium) can improve the electrocatalytic performance and stability of the coating and inhibit the excessive oxidation of manganese; Er (erbium) can improve the mechanical strength and corrosion resistance of the coating, promote the densification of the coating, and reduce defects; In the present invention, there may be one rare earth element, two, three, four, and so on.

[0037] In the present invention, rare earth elements such as La, Ce, Pr, Nd, Sm and Er all have unique 4 f The electronic structure of manganese can form stable composite oxides with manganese. These composite oxides show higher chemical inertness in strong acid environments and can effectively inhibit the excessive oxidation of manganese and prevent it from being converted into MnO which is easily soluble in acidic solutions. 4- .

[0038] When more than one rare earth element is used, not only can the performance of each rare earth element be exerted, but two or more rare earth elements can also produce a synergistic effect, for example: The introduction of Pr and Nd can enhance the conductivity and electrocatalytic performance of the coating and reduce the overpotential during electrolysis; La and Sm can improve the oxygen evolution reaction activity of the coating, making it exhibit higher electrocatalytic efficiency in an acidic environment; Ce and Nd can enhance the adhesion between the coating and the metal substrate, preventing the coating from falling off or peeling off during long-term use; etc.

[0039] In summary, the present invention can reduce the dependence on precious metals (such as Ru and Ir) by introducing rare earth elements, reduce the production cost of DSA anodes, and is suitable for large-scale industrial applications.

[0040] In some embodiments, the manganese-containing compound is at least one of manganese sulfate, manganese nitrate, manganese chloride and manganese acetate.

[0041] It should be noted that the manganese-containing compound can be manganese sulfate, manganese nitrate, manganese chloride or manganese acetate; The manganese-containing compound may be manganese sulfate, manganese nitrate, manganese chloride, manganese acetate, etc.; The manganese-containing compound may be manganese sulfate, manganese nitrate, manganese chloride and the like.

[0042] In the present invention, manganese sulfate, manganese nitrate, manganese chloride and manganese acetate have different solubility and ion mobility in aqueous solution. These characteristics will affect the diffusion and deposition behavior of manganese ions during electrodeposition, thereby affecting the uniformity and compactness of the coating. By selecting a suitable manganese-containing compound, the ion concentration and conductivity of the electrodeposition solution can be optimized to ensure that manganese ions and rare earth ions are uniformly co-deposited on the surface of the metal substrate to form a dense and uniform composite oxide coating.

[0043] Different manganese-containing compounds will form manganese oxides with different valence states during the electrodeposition process (such as Mn 2 O 3 , Mn 3 O 4 The manganese oxides formed by the electrodeposition of manganese chloride and manganese acetate have high electrocatalytic activity. The manganese oxides formed by the electrodeposition of manganese sulfate, manganese nitrate, manganese chloride and manganese acetate have stable potential windows and can meet the needs of various industrial environments (such as metallurgy, water treatment, electrolysis of water to produce hydrogen, etc.).

[0044] In some embodiments, the preprocessing comprises: The polished metal substrate is placed in a sodium hydroxide solution and heated for degreasing treatment; The metal substrate after degreasing treatment is placed in an oxalic acid solution and acid-etched at 90°C to 110°C for 1 h to 3 h to obtain a metal substrate with a pockmarked surface; The metal matrix is ​​any one of a Ti anode, a Pb-Ag anode and a conductive glass.

[0045] It should be noted that the grinding may include at least one of sandblasting and grinding; Among them, sandblasting refers to the use of compressed air or mechanical power to accelerate the spraying of abrasive particles (such as sand, steel shot, glass beads, etc.) onto the surface of the metal substrate. Under the impact of the abrasive particles, the oxide layer, rust, oil or other impurities on the surface can be removed, and a certain degree of roughness or texture can be formed on the surface. In the present invention, dry abrasive particles (such as quartz sand, steel sand, aluminum oxide, etc.) can be used to spray the metal substrate; Grinding refers to using sandpaper to grind the metal substrate after sandblasting to make the surface of the metal substrate have a certain degree of roughness; The temperature for heating for degreasing treatment can be 50 ℃ ~ 120 ℃, and the heating time can be 1 h ~ 3 h; The Ti anode has excellent electrical conductivity, corrosion resistance and mechanical strength. After pretreatment, it can form a strong bond with the rare earth-manganese oxide coating, significantly improving the chemical stability and electrocatalytic performance of the coating. The Pb-Ag anode exhibits good stability in a strong acid environment and can synergize with the rare earth-manganese oxide coating after pretreatment to enhance the corrosion resistance and electrocatalytic activity of the coating. Conductive glass is transparent and conductive, and after pretreatment it can be combined with a rare earth-manganese oxide coating for special applications such as photoelectrocatalysis.

[0046] In the present invention, the metal substrate is placed in a sodium hydroxide solution for heating and degreasing, which can remove oil and organic pollutants on the surface of the substrate and ensure that the surface of the substrate is clean. A clean surface is conducive to the uniform deposition and firm adhesion of the subsequent coating. The degreased metal substrate is placed in an oxalic acid solution and acid-etched for 1 h to 3 h at 90 ° C to 110 ° C to form a pockmarked structure on the surface of the substrate. This rough surface structure can increase the specific surface area of ​​the substrate and provide more attachment sites for the rare earth-manganese oxide coating, thereby enhancing the bonding strength between the coating and the substrate. Among them, the pockmarked surface structure formed by the acid etching treatment can promote the uniform distribution of the electrodeposition solution, ensure that the rare earth elements and manganese elements are uniformly co-deposited on the surface of the substrate, and form a dense and uniform composite oxide coating.

[0047] In some embodiments, the mass fraction of the sodium hydroxide solution is 5% to 20%; The mass fraction of the oxalic acid solution is 5% to 20%.

[0048] In specific implementation, the mass fraction of the sodium hydroxide solution can be 5%, 8%, 10%, 12%, 15%, 16%, 18%, 20%; The mass fraction of the oxalic acid solution can be 5%, 6%, 8%, 10%, 12%, 14%, 16%, 18%, and 20%.

[0049] In the present invention, the mass fraction of the sodium hydroxide solution affects the effect of the degreasing treatment. The set concentration range of 5% to 20% can ensure thorough degreasing while avoiding damage to the substrate material, and effectively remove oil stains and organic pollutants on the surface of the metal substrate, ensuring that the substrate surface is clean, providing a good foundation for subsequent acid etching and electrodeposition.

[0050] The mass fraction of oxalic acid solution affects the effect of acid etching. By setting the concentration range of 5%~20%, a uniform and moderate pockmarked structure can be formed on the substrate surface, increasing the specific surface area of ​​the substrate, improving the bonding strength between the coating and the substrate, and forming a uniform pockmarked structure on the surface of the metal substrate, providing more attachment sites for the rare earth-manganese oxide coating, and enhancing the bonding strength and uniformity of the coating.

[0051] In summary, in the present invention, by adjusting the concentrations of sodium hydroxide and oxalic acid solution, the surface of the pretreated metal substrate is clean and rough, which can significantly improve the bonding strength between the rare earth-manganese oxide coating and the substrate, and prevent the coating from falling off or peeling off during long-term use. After the pretreated metal substrate is combined with the rare earth-manganese oxide coating, it exhibits higher chemical stability in a strong acid environment, can effectively inhibit the excessive oxidation of manganese elements, and prevent it from being converted into MnO that is easily soluble in acidic solutions. 4- .

[0052] In some embodiments, the acid solution is at least one of sulfuric acid, nitric acid, hydrochloric acid, and acetic acid.

[0053] In the present invention, the acid solution in the electrodeposition solution mainly plays the role of adjusting the pH value, providing conductivity and stabilizing the ion concentration. Sulfuric acid, nitric acid, hydrochloric acid and acetic acid can all provide a stable acidic environment to ensure that the rare earth elements and manganese elements exist in a stable ionic form during the electrodeposition process, avoiding uneven deposition or coating defects caused by pH fluctuations.

[0054] In a specific implementation, sulfuric acid has strong acidity and high conductivity, and can provide a stable electrodeposition environment, promote uniform co-deposition of rare earth elements and manganese elements, and form a dense and uniform composite oxide coating; Nitric acid is oxidizing and can promote the oxidation of manganese during the electrodeposition process to form highly active manganese oxides, while optimizing the uniformity and density of the coating; Hydrochloric acid can provide chloride ions. The presence of chloride ions helps to adjust the crystallinity and surface morphology of the coating and improve the mechanical strength and corrosion resistance of the coating. Acetic acid is a weak acid that can provide a mild acidic environment suitable for acid-sensitive substrate materials (such as conductive glass) to promote uniform deposition of coatings.

[0055] The coatings formed by different acid solutions have different electronic structures and surface properties. For example, sulfuric acid and hydrochloric acid can improve the conductivity of the coating and reduce the overpotential during electrolysis. Sulfuric acid and hydrochloric acid are suitable for pretreatment and electrodeposition of Ti anodes, and can improve the bonding strength and corrosion resistance of the coating to the Ti substrate; Nitric acid and acetic acid are suitable for electrodeposition of Pb-Ag anodes, which can improve the uniformity and electrocatalytic performance of the coating; Acetic acid is suitable for electrodeposition of conductive glass and can provide a mild acidic environment to avoid damage to the base material.

[0056] In some embodiments, the method further comprises: The rare earth-manganese oxide coated anode is placed in a muffle furnace and annealed and calcined at 150° C. to 300° C. for 20 min to 120 min.

[0057] It should be noted that the rare earth-manganese oxide coated anode is placed in a muffle furnace and annealed and calcined at 150 ℃, 170 ℃, 190 ℃, 200 ℃, 220 ℃, 240 ℃, 260 ℃, 280 ℃, and 300 ℃ for 20 min, 40 min, 60 min, 80 min, 100 min, 110 min, and 120 min; the temperature range of 150 ℃ to 300 ℃ can ensure the performance of the coating while avoiding damage to the substrate material; the time range of 20 min to 120 min can ensure full optimization of the coating structure.

[0058] In the present invention, annealing and calcining can promote the crystallization of rare earth-manganese oxide in the coating, eliminate the amorphous or defective structure that may exist in the electrodeposition process, and thus improve the crystallinity and density of the coating. In the temperature range of 150 ° C to 300 ° C, the grains in the rare earth-manganese oxide coating gradually grow and form a stable crystal structure, reduce the pores and cracks in the coating, and improve the mechanical strength and corrosion resistance of the coating. Annealing and calcining can stabilize the valence state of manganese in the coating, preventing it from being over-oxidized to MnO soluble in acidic solution in a strong acid environment. 4- .

[0059] By limiting the annealing temperature and time, stable manganese oxides (such as Mn 2 O3 , Mn 3 O 4 The annealing process can significantly improve the chemical stability of the coating. The coating structure after annealing is more compact, which can effectively prevent the corrosion of the substrate material by the strong acid environment and extend the service life of the anode. Annealing and calcining can promote the electronic interaction between rare earth elements and manganese elements, optimize the electronic structure of the coating, and improve its electrocatalytic activity. Annealing and calcining can promote the interface diffusion between the coating and the metal substrate, forming a stronger chemical bond, thereby improving the bonding strength between the coating and the substrate and preventing the coating from falling off or peeling off during long-term use.

[0060] In a second aspect, the present invention provides a rare earth-manganese oxide coated anode, wherein the rare earth-manganese oxide coated anode is prepared by the method described in the first aspect.

[0061] In the present invention, the rare earth element in the rare earth-manganese oxide coating anode can stabilize the valence state of manganese and reduce the high-valence manganese (such as MnO 4- ) formation, thereby reducing the risk of dissolution and deactivation of manganese-based catalysts and extending the service life of the anode. The introduction of rare earth elements not only improves the stability of manganese-based oxides, but also enhances their electrocatalytic activity. The synergistic effect of rare earth elements and manganese elements can optimize the electronic structure of the coating, improve the catalytic efficiency of the anode in the oxygen evolution reaction (OER), reduce overpotential, and improve energy efficiency, making it suitable for use in long-term, high-intensity industrial production.

[0062] In some embodiments, the atomic percentage of rare earth element and manganese element in the rare earth-manganese oxide coated anode is 0.1%-20%.

[0063] It should be noted that the atomic percentage of rare earth elements and manganese elements can be 0.1%, 0.5%, 1%, 5%, 6%, 8%, 10%, 12%, 15%, 17%, 18%, and 20%.

[0064] In the present invention, the electronic structure and catalytic performance of the coating are further adjusted by setting the atomic percentage of rare earth elements and manganese elements (0.1%-20%), so that it still has excellent electrocatalytic activity while maintaining high stability.

[0065] By controlling the atomic percentage of rare earth elements between 0.1% and 20%, the catalytic effect of rare earth elements can be maximized while ensuring the stability of manganese-based oxides, inhibiting excessive oxidation of manganese elements and reducing the high-valent manganese (such as MnO 4- ) is formed, improving the chemical stability of the coating in a strong acid environment.

[0066] The atomic percentage of rare earth elements is controlled at 0.1%-20%. While ensuring the performance of the coating, it also avoids the cost increase caused by excessive use of rare earth elements, reduces material costs, and is suitable for large-scale industrial applications.

[0067] In order to enable those skilled in the art to more clearly understand the present invention, the method for preparing a rare earth-manganese oxide coating anode by electrodeposition according to the present invention is now described in detail through the following examples.

[0068] Example 1 (1) Grind the Ti substrate with sandpaper to make the surface of the Ti substrate have a certain degree of roughness; (2) The polished Ti substrate was placed in a 10% NaOH solution and heated at 100 °C for 2 h to remove surface oil stains; (3) The degreased Ti substrate was placed in a 10% oxalic acid solution and heated at 100 °C for 2 h to make its surface pockmarked; (4) preparing an electrodeposition solution by adding manganese sulfate powder to a 30 g / L sulfuric acid solution to make the manganese concentration 10 g / L, and then adding cerium sulfate to make the cerium concentration 1 g / L; (5) The Ti substrate treated in (3) was used as the anode and the cathode was a platinum electrode of the same size. A pulse power supply was used at 50 °C and 2 mA / cm 2 Pulse deposition was carried out at a current density of 100 nm, with a deposition time of 60 min, a working ratio of 20%, and a frequency of 10 Hz. A cerium-manganese oxide coating anode (CeMnO x / Ti); (6) The electrodeposited cerium-manganese oxide coated anode was placed in a muffle furnace and annealed at 250 °C for 2 h. After cooling, it was output as a product and labeled as CeMnO x / Ti.

[0069] Example 2 (1) Grind the Ti substrate with sandpaper to make the surface of the Ti substrate have a certain degree of roughness; (2) The polished Ti substrate was placed in a 5% NaOH solution and heated at 100 °C for 2 h to remove surface oil stains; (3) The degreased Ti substrate was then placed in a 5% oxalic acid solution and heated at 100 °C for 2 h to cause the surface to become pockmarked; (4) preparing an electrodeposition solution by adding manganese nitrate powder to a 25 g / L nitric acid solution to make the manganese concentration 10 g / L, and then adding cerium nitrate, neodymium nitrate, lanthanum nitrate, and praseodymium nitrate to make the concentrations of cerium, neodymium, lanthanum, and praseodymium each 0.3 g / L; (5) The Ti substrate treated in (3) was used as the anode and the cathode was a platinum electrode of the same size. A pulse power supply was used at 50 °C and 5 mA / cm 2 Pulse deposition was carried out at a current density of 100 μm, with a deposition time of 120 min, a working ratio of 10%, and a frequency of 5 Hz. A cerium-neodymium-lanthanum-praseodymium-manganese oxide coating anode was formed on the surface of the Ti substrate through oxidation reaction. (6) The electrodeposited cerium-neodymium-lanthanum-praseodymium-manganese oxide coating anode is placed in a muffle furnace and annealed at 350 °C for 2 h. After cooling, it is output as a product and marked as CeNdLaPrMnO x / Ti.

[0070] Comparative Example 1 is set based on Example 1. The difference between Comparative Example 1 and Example 1 is that: Comparative Example 1: Only a manganese oxide coating is provided on the Ti substrate without introducing rare earth elements. The obtained product is marked as MnO x / Ti.

[0071] Based on Example 1, Example 2 and Comparative Example 1, the coating anodes prepared in Example 1, Example 2 and Comparative Example 1 were tested respectively in 0.5 M sulfuric acid at -1 mA / cm 2 Accelerated life under current density, test results are as follows Figure 2 shown.

[0072] Figure 2 "MnO x / Ti" is the product prepared in Comparative Example 1, "CeMnO x / Ti" is the product prepared in Example 1, "CeNdLaPrMnO x / Ti" is the product prepared in Example 2.

[0073] according to Figure 2 It can be obtained that the accelerated life of the coated anode prepared in Example 1 of the present invention is greater than that in Comparative Example 1, which proves that the present invention can achieve better protection for the anode by introducing rare earth elements, improve its corrosion resistance and increase its service life.

[0074] The accelerated life of the coated anode prepared in Example 2 is greater than that in Example 1, which proves that increasing the types of rare earth elements on the basis of introducing rare earth elements is beneficial to further improve the corrosion resistance and other properties of the anode, thereby further improving the service life of the anode.

[0075] Example 3 (1) Grinding the Pb-Ag substrate with sandpaper to make the surface of the Pb-Ag substrate have a certain degree of roughness; (2) The polished Pb-Ag substrate was placed in a 5% NaOH solution and heated at 50 °C for 2 h to remove surface oil stains; (3) The degreased Ti substrate was then placed in a 5% oxalic acid solution and heated at 100 °C for 2 h to cause the surface to become pockmarked; (4) preparing an electrodeposition solution by adding manganese sulfate powder to a 15 g / L nitric acid solution to make the manganese concentration 15 g / L, and then adding cerium nitrate, neodymium nitrate, and lanthanum nitrate to make the cerium, neodymium, and lanthanum concentrations each 0.2 g / L; (5) The Pb-Ag substrate treated in (3) was used as the anode and the platinum electrode of the same size was used as the cathode. A pulse power supply was used at 40 °C and 10 mA / cm 2 Pulse deposition was carried out at a current density of 80 min, a working ratio of 20%, and a frequency of 20 Hz. A cerium-neodymium-lanthanum-manganese oxide coating anode was formed on the surface of the Pb-Ag substrate through oxidation reaction. (6) The electrodeposited cerium-neodymium-lanthanum-manganese oxide coated anode is placed in a muffle furnace and subjected to high temperature annealing at 350 °C for 2 h. After cooling, the anode is output as a product.

[0076] In summary, the present invention prepares a rare earth-manganese oxide coated anode by pulse deposition. Among them, rare earth oxide can refine the grains and enhance the catalytic activity and stability of the anode. The high temperature annealing process can further enhance the coating adhesion. The rare earth-manganese oxide coated anode is relatively cheap, and can increase the current density and improve production efficiency. The rare earth-manganese oxide coated anode has super corrosion resistance, is not easily dissolved during the electrolysis process, and can be used for a long period of time in multiple environmental systems such as acidic, alkaline and neutral.

[0077] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0078] Although the preferred embodiments of the present application have been described, those skilled in the art may make additional changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the embodiments of the present application.

[0079] Finally, it should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or terminal device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or terminal device. In the absence of further restrictions, the elements defined by the sentence "including one..." do not exclude the existence of other identical elements in the process, method, article or terminal device including the elements.

[0080] The above is a detailed introduction to a method for preparing a rare earth-manganese oxide coated anode by electrodeposition provided by the present invention. Specific examples are used herein to illustrate the principles and implementation methods of the present application. The description of the above embodiments is only used to help understand the method of the present application and its core idea. At the same time, for a person skilled in the art, according to the idea of ​​the present application, there will be changes in the specific implementation method and application scope. In summary, the content of this specification should not be understood as a limitation on the present application.

Claims

1. A method for preparing a rare earth-manganese oxide coated anode by electrodeposition, characterized in that: The method comprises: Taking appropriate amounts of rare earth element-containing compounds and manganese element-containing compounds and adding them into an acid solution to prepare an electrodeposition solution; wherein the rare earth element is a lanthanide element; Using the pretreated metal substrate as an anode and the platinum electrode as a cathode, pulse deposition is performed in the electrodeposition solution to form a rare earth-manganese oxide coating on the surface of the metal substrate through an oxidation reaction, thereby obtaining the rare earth-manganese oxide coating anode; In the electrodeposition solution, the concentration of the acid solution is 20 g / L-50 g / L, the concentration of the manganese element is 10 g / L-40 g / L, and the concentration of the rare earth element is 0.1%-20% of the concentration of the manganese element.

2. The method for preparing a rare earth-manganese oxide coated anode by electrodeposition according to claim 1, characterized in that: The current density of the pulse deposition was 0.2 mA / cm 2 ~10 mA / cm 2 , deposition time is 30 min~300 min, working ratio is 5%~50%, frequency is 5 Hz~15 Hz, and temperature is 25 ℃~100 ℃.

3. The method for preparing a rare earth-manganese oxide coated anode by electrodeposition according to claim 1, characterized in that: The rare earth element is at least one of La, Ce, Pr, Nd, Sm and Er.

4. The method for preparing a rare earth-manganese oxide coated anode by electrodeposition according to claim 1, characterized in that: The manganese-containing compound is at least one of manganese sulfate, manganese nitrate, manganese chloride and manganese acetate.

5. The method for preparing a rare earth-manganese oxide coated anode by electrodeposition according to claim 1, characterized in that: The pre-processing comprises: The polished metal substrate is placed in a sodium hydroxide solution and heated for degreasing treatment; The metal substrate after degreasing treatment is placed in an oxalic acid solution and acid-etched at 90°C to 110°C for 1 h to 3 h to obtain a metal substrate with a pockmarked surface; The metal matrix is ​​any one of a Ti anode, a Pb-Ag anode and a conductive glass.

6. The method for preparing a rare earth-manganese oxide coated anode by electrodeposition according to claim 5, characterized in that: The mass fraction of the sodium hydroxide solution is 5% to 20%; The mass fraction of the oxalic acid solution is 5% to 20%.

7. The method for preparing a rare earth-manganese oxide coated anode by electrodeposition according to claim 1, characterized in that: The acid solution is at least one of sulfuric acid, nitric acid, hydrochloric acid and acetic acid.

8. The method for preparing a rare earth-manganese oxide coated anode by electrodeposition according to any one of claims 1 to 7, characterized in that: The method further comprises: The rare earth-manganese oxide coated anode is placed in a muffle furnace and annealed and calcined at 150° C. to 300° C. for 20 min to 120 min.

9. A rare earth-manganese oxide coated anode, characterized in that: The rare earth-manganese oxide coated anode is prepared by the method according to any one of claims 1 to 8.

10. The rare earth-manganese oxide coated anode according to claim 9, characterized in that: In the rare earth-manganese oxide coated anode, the atomic percentage of rare earth element and manganese element is 0.1%-20%.

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