A cobalt phosphide composite electrode for energy-saving production of electrolytic manganese dioxide and a preparation method thereof

Abstract

This invention belongs to the field of electrolytic manganese dioxide production technology, and more specifically relates to a cobalt phosphide composite electrode for energy-saving electrolytic manganese dioxide production and its preparation method. This invention utilizes a eutectic ionic liquid as a solvent, a cobalt source as a reactant, and water as an optional additive. A cobalt-based precursor is prepared by electrodeposition; then, a cobalt phosphide composite electrode is prepared by gas-phase phosphating; finally, the cobalt phosphide composite electrode is coupled as a cathode into the electrolytic manganese dioxide production system, achieving energy-saving production of electrolytic manganese dioxide. This invention is simple to prepare, low in cost, low in energy consumption, highly controllable, reproducible, and has high mechanical strength, overcoming the shortcomings of existing technologies such as harsh process conditions, high cost, and high energy consumption.

Description

Technical Field

[0001] This invention belongs to the field of electrolytic manganese dioxide production technology, and more specifically relates to a cobalt phosphide composite electrode for energy-saving electrolytic manganese dioxide production and its preparation method. Background Technology

[0002] Electrolytic manganese dioxide (EMD), as an important chemical material, is widely used in batteries, electronic materials, catalysts, and other fields. Optimizing its production process is of great significance for promoting the development of related industries. The main production method for electrolytic manganese dioxide is electrolysis, which involves electrolyzing manganese dioxide ore or its precursors in an acidic electrolyte to obtain high-purity electrolytic manganese dioxide. However, traditional copper cathodes suffer from problems such as high energy consumption, poor electrode stability, low production efficiency, and low product purity during the electrolysis process.

[0003] Currently, some progress has been made in the research and development of cathode materials, but many shortcomings still exist. In some existing technologies, energy consumption has been reduced by using gas diffusion electrodes instead of hydrogen evolution cathodes, but the gas diffusion electrodes have complex structures and require the use of the precious metal platinum, resulting in high costs. In some existing technologies, non-metallic hybrid materials have been used instead of pure copper cathodes to avoid the contamination of the electrolyte by copper dissolution, but the preparation conditions are harsh and cumbersome and the energy consumption is high. In some existing technologies, carbon-carbon composite materials have been used instead of pure copper cathodes to avoid the impact of cathode aging on the microstructure of electrolytic manganese dioxide, but their catalytic activity is almost indistinguishable from that of pure copper.

[0004] Therefore, how to improve the hydrogen evolution activity of the cathode to reduce the power consumption of electrolytic manganese dioxide production while ensuring that the cathode preparation process is simple and low-cost has become an urgent technical problem to be solved in this field. Summary of the Invention

[0005] The purpose of this invention is to provide a cobalt phosphide composite electrode for energy-saving production of electrolytic manganese dioxide and its preparation method. An acid-resistant catalytic hydrogen evolution cathode is prepared by a two-step method of "electrodeposition-vapor phase phosphating" and coupled to the EMD electrolysis system to solve the problems existing in the prior art and realize energy-saving production of electrolytic manganese dioxide.

[0006] To achieve the above objectives, the present invention provides the following solution: One of the technical solutions of this invention is: a method for preparing a cobalt phosphide composite electrode for energy-saving production of electrolytic manganese dioxide, comprising the following steps: A cobalt source solution is obtained by mixing cobalt source, water, and a eutectic solvent. Using the cobalt source solution as the electrolyte and a conductive substrate as the cathode, an electrodeposition process is performed to obtain a cobalt-based precursor; The cobalt-based precursor was subjected to gas-phase phosphating under a protective atmosphere to obtain the cobalt phosphide composite electrode.

[0007] Furthermore, the cobalt source includes at least one of cobalt nitrate, cobalt chloride, and cobalt oxalate.

[0008] Furthermore, the hydrogen bond acceptor (HBA) of the eutectic solvent includes at least one of choline chloride (ChCl), tetrabutylammonium chloride (TBAC), and benzyltrimethylammonium chloride (BTMAC), and the hydrogen bond donor (HBD) includes at least one of ethylene glycol (EG), urea, and glycerol (Gly).

[0009] Optionally, the molar ratio of the hydrogen bond acceptor (HBA) to the hydrogen bond donor (HBD) is 1:1 to 1:5, preferably 1:2.

[0010] Furthermore, the concentration of cobalt(II) in the cobalt source solution is 0.05-0.5 mol / L.

[0011] Furthermore, the amount of water used in the cobalt source solution is 0-25 wt%.

[0012] Furthermore, the conductive substrate includes at least one of copper mesh, copper foam, and copper sheet.

[0013] Furthermore, the current density of the electrodeposition treatment is 0.6-1.5 mA / cm². 2 The power consumption is 5-25C / cm. 2 .

[0014] Furthermore, the protective atmosphere is an argon atmosphere or a nitrogen atmosphere.

[0015] Furthermore, the phosphating temperature of the gas-phase phosphating treatment is 300-600℃, the phosphating time is 2-5 h, and the phosphorus source includes at least one of sodium hypophosphite, sodium phosphite, and red phosphorus.

[0016] This invention utilizes a eutectic ionic liquid as a solvent, a cobalt source as a reactant, and water as an optional additive to prepare a cobalt-based precursor via electrodeposition. Then, a cobalt phosphide composite electrode is prepared using a vapor-phase phosphating method. Finally, the cobalt phosphide composite electrode is coupled as a cathode into an electrolytic manganese dioxide production system, enabling energy-efficient production of electrolytic manganese dioxide. This invention is simple to prepare, low in cost, low in energy consumption, highly controllable, reproducible, and exhibits high mechanical strength, overcoming the drawbacks of existing technologies such as stringent process conditions, high cost, and high energy consumption.

[0017] The second technical solution of the present invention provides a cobalt phosphide composite electrode, which is prepared by the above-described preparation method.

[0018] The third technical solution of the present invention provides an application of the above-mentioned cobalt phosphide composite electrode in the production of electrolytic manganese dioxide.

[0019] Furthermore, the electrolytic manganese dioxide production includes preparing electrolytic manganese dioxide under an acidic system.

[0020] The fourth technical solution of the present invention provides an energy-saving method for producing electrolytic manganese dioxide, wherein the above-mentioned cobalt phosphide composite electrode is used as a cathode coupled to the electrolytic manganese dioxide production system.

[0021] In this invention, the prepared cobalt phosphide composite electrode is used as a cathode and coupled to the electrolytic manganese dioxide production system, which can realize energy-saving production of electrolytic manganese dioxide.

[0022] Furthermore, the temperature of the electrolytic manganese dioxide production system is 80°C.

[0023] Furthermore, the electrolyte in the electrolytic manganese dioxide production system is 0.5 mol / L H2SO4 + 25 g / L Mn. 2+ Aqueous solution of (MnSO4).

[0024] The present invention discloses the following technical effects: The preparation method of this invention has advantages such as simple process, low price and significant energy saving effect.

[0025] The present invention provides a simple method for preparing cobalt phosphide composite electrodes, yields products with high purity (X-ray diffraction pattern) and excellent performance, and solves the problems of harsh preparation conditions and low hydrogen evolution catalytic activity of cathode materials prepared in the prior art, enabling efficient and energy-saving production of EMD.

[0026] The preparation method of the present invention can prepare a uniformly coated cobalt phosphide catalyst layer on a conductive substrate (such as a copper mesh), which is well adapted to EMD industrial production.

[0027] The eutectic ionic liquid used in this invention is green, environmentally friendly, easily degradable, and recyclable. Attached Figure Description

[0028] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings: Figure 1 This is a schematic diagram of the process flow for preparing a cobalt phosphide composite electrode for coupling the production of electrolytic manganese dioxide according to the present invention.

[0029] Figure 2 The LSV test results are for different electrodes prepared in Example 9, Comparative Example 1, and Comparative Example 2.

[0030] Figure 3The results of long-term stability tests on different electrodes prepared in Example 9, Comparative Example 1, and Comparative Example 2 are shown.

[0031] Figure 4 The cathode overpotential, anode potential, and cell voltage of different electrodes prepared for Example 9, Comparative Example 1, and Comparative Example 2, coupled as cathodes in the electrolytic manganese dioxide production system, are statistically analyzed.

[0032] Figure 5 The image shows the X-ray diffraction pattern of the cobalt phosphide composite electrode prepared in Example 9.

[0033] Figure 6 The image shows a SEM image of the cobalt phosphide composite electrode prepared in Example 9.

[0034] Figure 7 Electrochemical impedance spectroscopy of different electrodes prepared in Example 9, Comparative Example 1, and Comparative Example 2.

[0035] Figure 8 The image shows a bar chart of impedance data for different electrodes prepared in Example 9, Comparative Example 1, and Comparative Example 2.

[0036] Figure 9 The cobalt phosphide composite electrode prepared in Example 9 is used as the cathode and coupled to the electrolytic manganese dioxide production system. The X-ray diffraction pattern of the anode product is shown.

[0037] Figure 10 Different electrodes prepared for Example 9, Comparative Example 1, and Comparative Example 2 were used as cathodes and coupled to an electrolytic manganese dioxide production system. The power consumption and cost were statistically analyzed. Detailed Implementation

[0038] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0039] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0040] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0041] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0042] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0043] Unless otherwise specified, all raw materials and reagents involved in the specific embodiments of this invention are commercially available products.

[0044] Unless otherwise specified, room temperature and normal temperature in the specific embodiments of this invention refer to 20-30℃.

[0045] It should be noted that any aspects not described in detail in this invention are conventional practices in the field and are not the focus of this invention.

[0046] Example 1 The preparation steps of the cobalt phosphide composite electrode include: S1. Choline chloride and ethylene glycol are mixed in a molar ratio of 1:2 and continuously heated and stirred at 80°C until a transparent and uniform eutectic ionic liquid is obtained. Cobalt nitrate hexahydrate is added to the eutectic ionic liquid to make the cobalt salt concentration 0.1 mol / L. The mixture is stirred thoroughly at 80°C for 1 h to obtain a clear composite electrolyte.

[0047] S2. The conductive substrate (a 1cm × 2.5cm copper mesh) is ultrasonically treated in anhydrous ethanol for 5 min to remove organic matter from the substrate surface; then it is repeatedly rinsed with deionized water, and then ultrasonically treated in a 2 mol / L hydrochloric acid solution for 5 min to remove the oxide layer on the substrate surface; finally, it is repeatedly rinsed with deionized water and dried in a vacuum drying oven at 60℃ for 2 h to obtain the pretreated substrate.

[0048] S3. Using the pretreated substrate obtained in step S2 as the cathode and the dual graphite electrode as the anode, perform constant current electrodeposition with the following parameters: working area 1 cm × 1.5 cm, current density 1.5 mA / cm². 2 Deposition charge 20 C / cm 2 The deposition temperature was 80℃. After deposition, the electrode was washed sequentially with deionized water and anhydrous ethanol to remove residual electrolyte from the electrode surface, and then dried in a vacuum drying oven at 60℃ for 2 h to obtain the cobalt-based precursor.

[0049] S4. Place the cobalt-based precursor and sodium hypophosphite in a tube furnace at a mass ratio of 1:5, continuously introduce argon gas into the tube furnace, heat to 400℃ at a rate of 5 ℃ / min and hold for 2 h, then allow to cool naturally to room temperature to obtain a cobalt phosphide composite electrode.

[0050] Example 2 The preparation steps of the cobalt phosphide composite electrode include: S1. Choline chloride and ethylene glycol are mixed in a molar ratio of 1:2 and continuously heated and stirred at 80°C until a transparent and uniform eutectic ionic liquid is obtained. Cobalt nitrate hexahydrate and water are added to the eutectic ionic liquid to make the cobalt salt concentration 0.1 mol / L and the water content 5 wt.%. The mixture is stirred thoroughly at 80°C for 1 h to obtain a clear composite electrolyte.

[0051] S2. The conductive substrate (a 1cm × 2.5cm copper mesh) is ultrasonically treated in anhydrous ethanol for 5 min to remove organic matter from the substrate surface; then it is repeatedly rinsed with deionized water, and then ultrasonically treated in a 2 mol / L hydrochloric acid solution for 5 min to remove the oxide layer on the substrate surface; finally, it is repeatedly rinsed with deionized water and dried in a vacuum drying oven at 60℃ for 2 h to obtain the pretreated substrate.

[0052] S3. Using the pretreated substrate obtained in step S2 as the cathode and the dual graphite electrode as the anode, perform constant current electrodeposition with the following parameters: working area 1 cm × 1.5 cm, current density 1.5 mA / cm². 2 Deposition charge 20 C / cm 2 The deposition temperature was 80℃. After deposition, the electrode was washed sequentially with deionized water and anhydrous ethanol to remove residual electrolyte from the electrode surface, and then dried in a vacuum drying oven at 60℃ for 2 h to obtain the cobalt-based precursor.

[0053] S4. Place the cobalt-based precursor and sodium hypophosphite in a tube furnace at a mass ratio of 1:5, continuously introduce argon gas into the tube furnace, heat to 400℃ at a rate of 5 ℃ / min and hold for 2 h, then allow to cool naturally to room temperature to obtain a cobalt phosphide composite electrode.

[0054] Example 3 The preparation steps of the cobalt phosphide composite electrode include: S1. Choline chloride and ethylene glycol are mixed in a molar ratio of 1:2 and continuously heated and stirred at 80°C until a transparent and uniform eutectic ionic liquid is obtained. Cobalt nitrate hexahydrate and water are added to the eutectic ionic liquid to make the cobalt salt concentration 0.1 mol / L and the water content 15 wt.%. The mixture is stirred thoroughly at 80°C for 1 h to obtain a clear composite electrolyte.

[0055] S2. The conductive substrate (a 1cm × 2.5cm copper mesh) is ultrasonically treated in anhydrous ethanol for 5 min to remove organic matter from the substrate surface; then it is repeatedly rinsed with deionized water, and then ultrasonically treated in a 2 mol / L hydrochloric acid solution for 5 min to remove the oxide layer on the substrate surface; finally, it is repeatedly rinsed with deionized water and dried in a vacuum drying oven at 60℃ for 2 h to obtain the pretreated substrate.

[0056] S3. Using the pretreated substrate obtained in step S2 as the cathode and the dual graphite electrode as the anode, perform constant current electrodeposition with the following parameters: working area 1 cm × 1.5 cm, current density 1.5 mA / cm². 2 Deposition charge 20 C / cm 2 The deposition temperature was 80℃. After deposition, the electrode was washed sequentially with deionized water and anhydrous ethanol to remove residual electrolyte from the electrode surface, and then dried in a vacuum drying oven at 60℃ for 2 h to obtain the cobalt-based precursor.

[0057] S4. Place the cobalt-based precursor and sodium hypophosphite in a tube furnace at a mass ratio of 1:5, continuously introduce argon gas into the tube furnace, heat to 400℃ at a rate of 5 ℃ / min and hold for 2 h, then allow to cool naturally to room temperature to obtain a cobalt phosphide composite electrode.

[0058] Example 4 The preparation steps of the cobalt phosphide composite electrode include: S1. Choline chloride and ethylene glycol are mixed in a molar ratio of 1:2 and continuously heated and stirred at 80°C until a transparent and uniform eutectic ionic liquid is obtained. Cobalt nitrate hexahydrate and water are added to the eutectic ionic liquid to make the cobalt salt concentration 0.1 mol / L and the water content 20 wt.%. The mixture is stirred thoroughly at 80°C for 1 h to obtain a clear composite electrolyte.

[0059] S2. The conductive substrate (a 1cm × 2.5cm copper mesh) is ultrasonically treated in anhydrous ethanol for 5 min to remove organic matter from the substrate surface; then it is repeatedly rinsed with deionized water, and then ultrasonically treated in a 2 mol / L hydrochloric acid solution for 5 min to remove the oxide layer on the substrate surface; finally, it is repeatedly rinsed with deionized water and dried in a vacuum drying oven at 60℃ for 2 h to obtain the pretreated substrate.

[0060] S3. Using the pretreated substrate obtained in step S2 as the cathode and the dual graphite electrode as the anode, perform constant current electrodeposition with the following parameters: working area 1 cm × 1.5 cm, current density 1.5 mA / cm². 2 Deposition charge 20 C / cm 2 The deposition temperature was 80℃. After deposition, the electrode was washed sequentially with deionized water and anhydrous ethanol to remove residual electrolyte from the electrode surface, and then dried in a vacuum drying oven at 60℃ for 2 h to obtain the cobalt-based precursor.

[0061] S4. Place the cobalt-based precursor and sodium hypophosphite in a tube furnace at a mass ratio of 1:5, continuously introduce argon gas into the tube furnace, heat to 400℃ at a rate of 5 ℃ / min and hold for 2 h, then allow to cool naturally to room temperature to obtain a cobalt phosphide composite electrode.

[0062] Example 5 The preparation steps of the cobalt phosphide composite electrode include: S1. Choline chloride and ethylene glycol are mixed in a molar ratio of 1:2 and continuously heated and stirred at 80°C until a transparent and uniform eutectic ionic liquid is obtained. Cobalt nitrate hexahydrate and water are added to the eutectic ionic liquid to make the cobalt salt concentration 0.1 mol / L and the water content 25 wt.%. The mixture is stirred thoroughly at 80°C for 1 h to obtain a clear composite electrolyte.

[0063] S2. The conductive substrate (a 1cm × 2.5cm copper mesh) is ultrasonically treated in anhydrous ethanol for 5 min to remove organic matter from the substrate surface; then it is repeatedly rinsed with deionized water, and then ultrasonically treated in a 2 mol / L hydrochloric acid solution for 5 min to remove the oxide layer on the substrate surface; finally, it is repeatedly rinsed with deionized water and dried in a vacuum drying oven at 60℃ for 2 h to obtain the pretreated substrate.

[0064] S3. Using the pretreated substrate obtained in step S2 as the cathode and the dual graphite electrode as the anode, perform constant current electrodeposition with the following parameters: working area 1 cm × 1.5 cm, current density 1.5 mA / cm². 2 Deposition charge 20 C / cm 2The deposition temperature was 80℃. After deposition, the electrode was washed sequentially with deionized water and anhydrous ethanol to remove residual electrolyte from the electrode surface, and then dried in a vacuum drying oven at 60℃ for 2 h to obtain the cobalt-based precursor.

[0065] S4. Place the cobalt-based precursor and sodium hypophosphite in a tube furnace at a mass ratio of 1:5, continuously introduce argon gas into the tube furnace, heat to 400℃ at a rate of 5 ℃ / min and hold for 2 h, then allow to cool naturally to room temperature to obtain a cobalt phosphide composite electrode.

[0066] Example 6 The preparation steps of the cobalt phosphide composite electrode include: S1. Choline chloride and ethylene glycol are mixed in a molar ratio of 1:2 and continuously heated and stirred at 80°C until a transparent and uniform eutectic ionic liquid is obtained. Cobalt nitrate hexahydrate and water are added to the eutectic ionic liquid to make the cobalt salt concentration 0.1 mol / L and the water content 15 wt.%. The mixture is stirred thoroughly at 80°C for 1 h to obtain a clear composite electrolyte.

[0067] S2. The conductive substrate (a 1cm × 2.5cm copper mesh) is ultrasonically treated in anhydrous ethanol for 5 min to remove organic matter from the substrate surface; then it is repeatedly rinsed with deionized water, and then ultrasonically treated in a 2 mol / L hydrochloric acid solution for 5 min to remove the oxide layer on the substrate surface; finally, it is repeatedly rinsed with deionized water and dried in a vacuum drying oven at 60℃ for 2 h to obtain the pretreated substrate.

[0068] S3. Using the pretreated substrate obtained in step S2 as the cathode and the dual graphite electrode as the anode, perform constant current electrodeposition with the following parameters: working area 1 cm × 1.5 cm, current density 1.5 mA / cm². 2 Deposition charge 20 C / cm 2 The deposition temperature was 80℃. After deposition, the electrode was washed sequentially with deionized water and anhydrous ethanol to remove residual electrolyte from the electrode surface, and then dried in a vacuum drying oven at 60℃ for 2 h to obtain the cobalt-based precursor.

[0069] S4. Place the cobalt-based precursor and sodium hypophosphite in a tube furnace at a mass ratio of 1:5, continuously introduce argon gas into the tube furnace, heat to 300℃ at a rate of 5 ℃ / min and hold for 2 h, then allow to cool naturally to room temperature to obtain a cobalt phosphide composite electrode.

[0070] Example 7 The preparation steps of the cobalt phosphide composite electrode include: S1. Choline chloride and ethylene glycol are mixed in a molar ratio of 1:2 and continuously heated and stirred at 80°C until a transparent and uniform eutectic ionic liquid is obtained. Cobalt nitrate hexahydrate and water are added to the eutectic ionic liquid to make the cobalt salt concentration 0.1 mol / L and the water content 15 wt.%. The mixture is stirred thoroughly at 80°C for 1 h to obtain a clear composite electrolyte.

[0071] S2. The conductive substrate (a 1cm × 2.5cm copper mesh) is ultrasonically treated in anhydrous ethanol for 5 min to remove organic matter from the substrate surface; then it is repeatedly rinsed with deionized water, and then ultrasonically treated in a 2 mol / L hydrochloric acid solution for 5 min to remove the oxide layer on the substrate surface; finally, it is repeatedly rinsed with deionized water and dried in a vacuum drying oven at 60℃ for 2 h to obtain the pretreated substrate.

[0072] S3. Using the pretreated substrate obtained in step S2 as the cathode and the dual graphite electrode as the anode, perform constant current electrodeposition with the following parameters: working area 1 cm × 1.5 cm, current density 1.5 mA / cm². 2 Deposition charge 20 C / cm 2 The deposition temperature was 80℃. After deposition, the electrode was washed sequentially with deionized water and anhydrous ethanol to remove residual electrolyte from the electrode surface, and then dried in a vacuum drying oven at 60℃ for 2 h to obtain the cobalt-based precursor.

[0073] S4. Place the cobalt-based precursor and sodium hypophosphite in a tube furnace at a mass ratio of 1:5, continuously introduce argon gas into the tube furnace, heat to 500℃ at a rate of 5℃ / min and hold for 2 h, then allow to cool naturally to room temperature to obtain a cobalt phosphide composite electrode.

[0074] Example 8 The preparation steps of the cobalt phosphide composite electrode include: S1. Choline chloride and ethylene glycol are mixed in a molar ratio of 1:2 and continuously heated and stirred at 80°C until a transparent and uniform eutectic ionic liquid is obtained. Cobalt nitrate hexahydrate and water are added to the eutectic ionic liquid to make the cobalt salt concentration 0.1 mol / L and the water content 15 wt.%. The mixture is stirred thoroughly at 80°C for 1 h to obtain a clear composite electrolyte.

[0075] S2. The conductive substrate (a 1cm × 2.5cm copper mesh) is ultrasonically treated in anhydrous ethanol for 5 min to remove organic matter from the substrate surface; then it is repeatedly rinsed with deionized water, and then ultrasonically treated in a 2 mol / L hydrochloric acid solution for 5 min to remove the oxide layer on the substrate surface; finally, it is repeatedly rinsed with deionized water and dried in a vacuum drying oven at 60℃ for 2 h to obtain the pretreated substrate.

[0076] S3. Using the pretreated substrate obtained in step S2 as the cathode and the dual graphite electrode as the anode, perform constant current electrodeposition with the following parameters: working area 1 cm × 1.5 cm, current density 1.5 mA / cm². 2 Deposition charge 20 C / cm 2 The deposition temperature was 80℃. After deposition, the electrode was washed sequentially with deionized water and anhydrous ethanol to remove residual electrolyte from the electrode surface, and then dried in a vacuum drying oven at 60℃ for 2 h to obtain the cobalt-based precursor.

[0077] S4. Place the cobalt-based precursor and sodium hypophosphite in a tube furnace at a mass ratio of 1:5, continuously introduce argon gas into the tube furnace, heat to 600℃ at a rate of 5℃ / min and hold for 2 h, then allow to cool naturally to room temperature to obtain a cobalt phosphide composite electrode.

[0078] Example 9 The preparation steps of the cobalt phosphide composite electrode include: S1. Choline chloride and ethylene glycol are mixed in a molar ratio of 1:2 and continuously heated and stirred at 80°C until a transparent and uniform eutectic ionic liquid is obtained. Cobalt nitrate hexahydrate and water are added to the eutectic ionic liquid to make the cobalt salt concentration 0.1 mol / L and the water content 15 wt.%. The mixture is stirred thoroughly at 80°C for 1 h to obtain a clear composite electrolyte.

[0079] S2. The conductive substrate (a 1cm × 2.5cm copper mesh) is ultrasonically treated in anhydrous ethanol for 5 min to remove organic matter from the substrate surface; then it is repeatedly rinsed with deionized water, and then ultrasonically treated in a 2 mol / L hydrochloric acid solution for 5 min to remove the oxide layer on the substrate surface; finally, it is repeatedly rinsed with deionized water and dried in a vacuum drying oven at 60℃ for 2 h to obtain the pretreated substrate.

[0080] S3. Using the pretreated substrate obtained in step S2 as the cathode and the dual graphite electrode as the anode, perform constant current electrodeposition with the following parameters: working area 1 cm × 1.5 cm, current density 1.5 mA / cm². 2 Deposition charge 20 C / cm 2 The deposition temperature was 80℃. After deposition, the electrode was washed sequentially with deionized water and anhydrous ethanol to remove residual electrolyte from the electrode surface, and then dried in a vacuum drying oven at 60℃ for 2 h to obtain the cobalt-based precursor.

[0081] S4. Place the cobalt-based precursor and sodium hypophosphite in a tube furnace at a mass ratio of 1:5, continuously introduce argon gas into the tube furnace, heat to 400℃ at a rate of 5 ℃ / min and hold for 3 h, then naturally cool to room temperature to obtain a cobalt phosphide composite electrode.

[0082] Example 10 The preparation steps of the cobalt phosphide composite electrode include: S1. Choline chloride and ethylene glycol are mixed in a molar ratio of 1:2 and continuously heated and stirred at 80°C until a transparent and uniform eutectic ionic liquid is obtained. Cobalt nitrate hexahydrate and water are added to the eutectic ionic liquid to make the cobalt salt concentration 0.1 mol / L and the water content 15 wt.%. The mixture is stirred thoroughly at 80°C for 1 h to obtain a clear composite electrolyte.

[0083] S2. The conductive substrate (a 1cm × 2.5cm copper mesh) is ultrasonically treated in anhydrous ethanol for 5 min to remove organic matter from the substrate surface; then it is repeatedly rinsed with deionized water, and then ultrasonically treated in a 2 mol / L hydrochloric acid solution for 5 min to remove the oxide layer on the substrate surface; finally, it is repeatedly rinsed with deionized water and dried in a vacuum drying oven at 60℃ for 2 h to obtain the pretreated substrate.

[0084] S3. Using the pretreated substrate obtained in step S2 as the cathode and the dual graphite electrode as the anode, perform constant current electrodeposition with the following parameters: working area 1 cm × 1.5 cm, current density 1.5 mA / cm². 2 Deposition charge 20 C / cm 2 The deposition temperature was 80℃. After deposition, the electrode was washed sequentially with deionized water and anhydrous ethanol to remove residual electrolyte from the electrode surface, and then dried in a vacuum drying oven at 60℃ for 2 h to obtain the cobalt-based precursor.

[0085] S4. Place the cobalt-based precursor and sodium hypophosphite in a tube furnace at a mass ratio of 1:5, continuously introduce argon gas into the tube furnace, heat to 400℃ at a rate of 5℃ / min and hold for 4 h, then allow to cool naturally to room temperature to obtain a cobalt phosphide composite electrode.

[0086] Example 11 The preparation steps of the cobalt phosphide composite electrode include: S1. Choline chloride and ethylene glycol are mixed in a molar ratio of 1:2 and continuously heated and stirred at 80°C until a transparent and uniform eutectic ionic liquid is obtained. Cobalt nitrate hexahydrate and water are added to the eutectic ionic liquid to make the cobalt salt concentration 0.1 mol / L and the water content 15 wt.%. The mixture is stirred thoroughly at 80°C for 1 h to obtain a clear composite electrolyte.

[0087] S2. The conductive substrate (a 1cm × 2.5cm copper mesh) is ultrasonically treated in anhydrous ethanol for 5 min to remove organic matter from the substrate surface; then it is repeatedly rinsed with deionized water, and then ultrasonically treated in a 2 mol / L hydrochloric acid solution for 5 min to remove the oxide layer on the substrate surface; finally, it is repeatedly rinsed with deionized water and dried in a vacuum drying oven at 60℃ for 2 h to obtain the pretreated substrate.

[0088] S3. Using the pretreated substrate obtained in step S2 as the cathode and the dual graphite electrode as the anode, perform constant current electrodeposition with the following parameters: working area 1 cm × 1.5 cm, current density 1.5 mA / cm². 2 Deposition charge 20 C / cm 2 The deposition temperature was 80℃. After deposition, the electrode was washed sequentially with deionized water and anhydrous ethanol to remove residual electrolyte from the electrode surface, and then dried in a vacuum drying oven at 60℃ for 2 h to obtain the cobalt-based precursor.

[0089] S4. Place the cobalt-based precursor and sodium hypophosphite in a tube furnace at a mass ratio of 1:5, continuously introduce argon gas into the tube furnace, heat to 400℃ at a rate of 5℃ / min and hold for 5 h, then allow to cool naturally to room temperature to obtain the cobalt phosphide composite electrode.

[0090] Comparative Example 1 The preparation steps of the copper phosphide electrode include: S1. The substrate (a 1 cm × 2.5 cm copper mesh) is ultrasonically treated in anhydrous ethanol for 5 min to remove organic matter from the substrate surface; then it is repeatedly rinsed with deionized water, and then ultrasonically treated in a 2 mol / L hydrochloric acid solution for 5 min to remove the oxide layer on the substrate surface; finally, it is repeatedly rinsed with deionized water and dried in a vacuum drying oven at 60℃ for 2 h to obtain the pretreated substrate.

[0091] S2. The pretreated matrix obtained in step S1 and sodium hypophosphite are placed in a tube furnace at a mass ratio of 1:5. Argon gas is continuously introduced into the tube furnace, and the temperature is raised to 400℃ at a rate of 5℃ / min and held for 3 hours. The temperature is then naturally cooled to room temperature to obtain a copper phosphide electrode.

[0092] Comparative Example 2 The preparation steps of the copper electrode include: The substrate (a 1 cm × 2.5 cm copper mesh) was ultrasonically treated in anhydrous ethanol for 5 min to remove organic matter from the substrate surface; then it was repeatedly rinsed with deionized water and ultrasonically treated in a 2 mol / L hydrochloric acid solution for 5 min to remove the oxide layer on the substrate surface; finally, it was repeatedly rinsed with deionized water and dried in a vacuum drying oven at 60℃ for 2 h to obtain a clean copper electrode.

[0093] Test case The electrodes prepared in the examples and comparative examples were coupled into the electrolytic manganese dioxide production system, and the specific steps are as follows: With 0.5 mol / L H2SO4 + 25 g / L Mn 2+ An aqueous solution of (MnSO4) was used as the electrolyte. The electrode prepared in the examples or comparative examples was used as the cathode, and activated carbon paper was used as the anode (replaced every 24 hours). The cathode / anode potential was monitored with a multimeter, and the current density was 10 mA / cm². 2 An electrolytic manganese dioxide production system was constructed in a quartz electrolytic cell, with the temperature controlled at 80℃ and the system circulation rate at 200 mL / min. The coupling performance of each electrode is statistically analyzed, as shown in Table 1.

[0094] Table 1 As can be seen from Table 1, Comparative Example 2 is a pure copper cathode, which has the worst hydrogen evolution performance, the highest cell voltage, and the largest power consumption; Comparative Example 1 is a copper phosphide cathode obtained by direct phosphating of copper mesh, which has better hydrogen evolution performance than the pure copper cathode but is significantly weaker than the cobalt phosphide composite electrode. This proves that the substance that plays a decisive catalytic role in the cobalt phosphide composite electrode is cobalt phosphide rather than copper phosphide.

[0095] Figure 1 This is a schematic diagram of the process flow for preparing a cobalt phosphide composite electrode for coupling the production of electrolytic manganese dioxide according to the present invention.

[0096] Figure 2 The LSV test results are for different electrodes prepared in Example 9, Comparative Example 1, and Comparative Example 2.

[0097] Figure 3 The results of long-term stability tests on different electrodes prepared in Example 9, Comparative Example 1, and Comparative Example 2 are shown.

[0098] from Figures 2-3 As can be seen, the cobalt phosphide composite electrode provided by the present invention has significant advantages in HER performance and its lifespan is significantly better than that of the comparative electrode.

[0099] Figure 4 The cathode overpotential, anode potential, and cell voltage of different electrodes prepared for Example 9, Comparative Example 1, and Comparative Example 2, coupled as cathodes in the electrolytic manganese dioxide production system, are statistically analyzed. As can be seen from the figure, compared to the cell voltages of Comparative Example 1 and Comparative Example 2 (1.65V and 1.79V), the cobalt phosphide composite electrode prepared in Example 9 exhibits a significant energy-saving effect in the coupling system, with the cell voltage reduced by up to 310mV.

[0100] Figure 5The X-ray diffraction pattern of the cobalt phosphide composite electrode prepared in Example 9 is shown in the figure. As can be seen from the figure, Cu3P (PDF#04-004-8619) diffraction peaks exist at 2θ of 35.85°, 38.88°, 41.30°, 44.78° and 45.93°, and diffraction peaks also appear at 2θ of 31.6°, 48.12° and 56.74°, which correspond to the (011), (211) and (301) crystal planes of CoP (PDF#09-0497), respectively. In summary, the phase composition of the cobalt phosphide composite electrode is a mixture of CoP and Cu3P.

[0101] Figure 6 The image shows a SEM image of the cobalt phosphide composite electrode prepared in Example 9. As can be seen from the image, the surface of the cobalt phosphide composite electrode exhibits a three-dimensional "cauliflower-like" structure composed of spherical nanoparticle clusters. This unique three-dimensional "cauliflower-like" structure can expose more active sites, which is beneficial for the adsorption / desorption of hydrogen evolution reaction intermediates on the electrode surface.

[0102] Figure 7 Electrochemical impedance spectroscopy of different electrodes prepared in Example 9, Comparative Example 1, and Comparative Example 2.

[0103] Figure 8 The image shows a bar chart of impedance data for different electrodes prepared in Example 9, Comparative Example 1, and Comparative Example 2.

[0104] Depend on Figures 7-8 It can be seen that the cobalt phosphide composite electrode prepared in Example 9 has the lowest charge transfer resistance (R0). ct This indicates that phosphating effectively reconstructs the electron transport channels at the electrode interface, increases the density of active sites, and thus significantly reduces charge transfer resistance, resulting in optimal catalytic reaction kinetics.

[0105] Figure 9 The cobalt phosphide composite electrode prepared in Example 9 was used as the cathode and coupled to the electrolytic manganese dioxide production system. The X-ray diffraction pattern of the anode product is shown in the figure. As can be seen from the figure, the product is pure γ-type electrolytic manganese dioxide.

[0106] Figure 10 Different electrodes prepared for Examples 9, 1, and 2 were used as cathodes in the coupled electrolytic manganese dioxide production system. Power consumption and cost statistics were compiled. As shown in the figure, compared to the pure copper cathode widely used in current processes, the cobalt phosphide composite electrode exhibits a significant advantage in power consumption (1161.82 kWh / t → 960.61 kWh / t). Based on an industrial electricity price of RMB 0.4 / kWh, the power cost is reduced by RMB 86.52 / t. In 2025, China's EMD production is estimated at approximately 280,000 tons. Industrializing this process could save 5.6 × 10⁻⁶ kWh of electricity annually. 7The electricity cost can be reduced by approximately 22.4 million yuan per kWh.

[0107] In summary, the cobalt phosphide composite electrode for energy-saving electrolytic manganese dioxide production provided by this invention solves the problems of high energy consumption and poor stability caused by insufficient hydrogen evolution activity of existing copper cathodes used in electrolytic manganese dioxide production. The electrode preparation method includes two main steps: "electrodeposition in a eutectic solvent system" and "low-temperature vapor-phase phosphating," after which the cobalt phosphide composite electrode is coupled to the electrolytic manganese dioxide production system. The cobalt phosphide composite electrode prepared by this invention exhibits excellent electrocatalytic hydrogen evolution performance in a high-temperature acidic system, with good controllability, an environmentally friendly preparation process, low cost, and ease of large-scale production. Compared with existing pure copper cathodes, the cobalt phosphide composite electrode of this invention can effectively reduce the cathode hydrogen evolution overpotential, lower the cell voltage of the electrolytic system, and achieve significant energy savings.

[0108] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0109] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing a cobalt phosphide composite electrode for energy-saving production of electrolytic manganese dioxide, characterized in that the steps include... include: A cobalt source solution is obtained by mixing cobalt source, water, and a eutectic solvent. Using the cobalt source solution as the electrolyte and a conductive substrate as the cathode, an electrodeposition process is performed to obtain a cobalt-based precursor; The cobalt-based precursor was subjected to gas-phase phosphating under a protective atmosphere to obtain the cobalt phosphide composite electrode.

2. The preparation method according to claim 1, characterized in that, The hydrogen bond acceptor of the eutectic solvent includes at least one of choline chloride, tetrabutylammonium chloride, and benzyltrimethylammonium chloride, and the hydrogen bond donor includes at least one of ethylene glycol, urea, and glycerol.

3. The preparation method according to claim 2, characterized in that, The molar ratio of the hydrogen bond acceptor to the hydrogen bond donor is 1:1 to 1:

5.

4. The preparation method according to claim 1, characterized in that, The concentration of cobalt(II) in the cobalt source solution is 0.05-0.5 mol / L; And / or, the amount of water used in the cobalt source solution is 0-25 wt%.

5. The preparation method according to claim 1, characterized in that, The conductive substrate includes at least one of copper mesh, copper foam, and copper sheet; And / or, the cobalt source includes at least one of cobalt nitrate, cobalt chloride, and cobalt oxalate.

6. The preparation method according to claim 1, characterized in that, The current density for the electrodeposition process is 0.6-1.5 mA / cm². 2 The power consumption is 5-25C / cm. 2 ; And / or, the protective atmosphere is an argon atmosphere or a nitrogen atmosphere.

7. The preparation method according to claim 1, characterized in that, The phosphating temperature of the gas-phase phosphating treatment is 300-600℃, the phosphating time is 2-5 h, and the phosphorus source includes at least one of sodium hypophosphite, sodium phosphite and red phosphorus.

8. A cobalt phosphide composite electrode, characterized in that, The cobalt phosphide composite electrode is prepared by the preparation method according to any one of claims 1-7.

9. The application of the cobalt phosphide composite electrode according to claim 8 in the production of electrolytic manganese dioxide.

10. A method for energy-saving production of electrolytic manganese dioxide, characterized in that, In the method, the cobalt phosphide composite electrode as described in claim 8 is used as the cathode and coupled to the electrolytic manganese dioxide production system.

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