Manganese-doped modified non-noble metal-based hydroxide oxygen evolution electrocatalyst as well as preparation method and application thereof

Abstract

The invention discloses a manganese-doped modified non-noble metal-based hydroxide oxygen evolution electrocatalyst and a preparation method and application thereof, and belongs to the technical field of water electrolysis hydrogen production catalysts, the catalyst is composed of a manganese-doped modified non-noble metal hydroxide active phase and a conductive substrate, the preparation method comprises the following steps: ultrasonically cleaning a conductive substrate with acid, deionized water and ethanol respectively; the preparation method comprises the following steps: dissolving 2, 5-dicarboxyl terephthalic acid and transition metal salt in N, N-dimethylformamide, and preparing and reacting to obtain a precursor solution; pouring into a reaction kettle, reacting with a conductive substrate, and growing a non-noble metal hydroxide active phase with a nano structure on the surface of the conductive substrate; putting into a reaction kettle, dissolving manganese metal salt into methanol, adding into the reaction kettle, and carrying out solvothermal reaction; the catalyst has the advantages of being high in fineness, not prone to agglomeration, high in oxygen evolution reaction activity and good in catalytic performance, and can keep high activity and long-term stability under the actual working condition reaction temperature condition.

Description

Technical Field

[0001] The present invention relates to a manganese-doped modified non-noble metal-based hydroxide oxygen evolution electrocatalyst, a preparation method thereof and an application thereof, and belongs to the technical field of electrocatalysts for hydrogen production by electrolyzing water. Background Art

[0002] As a green sustainable energy carrier with high energy density and zero carbon emissions, hydrogen energy is an indispensable part of the future sustainable clean energy system. Integrating renewable energy with the electrolytic water hydrogen production technology to produce "green hydrogen" can achieve zero carbon emissions. In the process of electrolytic water hydrogen production, compared with the two-electron hydrogen evolution reaction, the four-electron oxygen evolution reaction has slow kinetics, which limits the energy conversion and storage efficiency. Therefore, higher requirements are put forward for the activity of the oxygen evolution catalyst. In recent years, in the field of electrolytic water hydrogen production technology, developing new non-noble metal catalysts to reduce the material cost and pursuing excellent catalytic performance has become the main trend. However, the existing non-noble metal catalysts have the following defects: First, the preparation methods mainly adopt the calcination method or the hydrothermal method, etc. The calcination method requires calcination and subsequent grinding steps, and the process is cumbersome. The hydrothermal method is difficult to reach a high reaction air pressure, which will result in low fineness of the finally prepared catalyst product, easy agglomeration, and affect its catalytic performance. In addition, under actual working conditions, due to the generation of dynamic waste heat caused by entropy increase, the entire catalytic reaction system operates in the range of 30-80 o °C, and the existing non-noble metal catalysts have low oxygen evolution reaction activity and are difficult to maintain high activity and long-term stability in the above temperature environment. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to overcome the defects of the prior art and provide a manganese-doped modified non-noble metal-based hydroxide oxygen evolution electrocatalyst, a preparation method thereof and an application thereof, which have the advantages of high fineness, not easy to agglomerate, high oxygen evolution reaction activity and good catalytic performance, and can maintain high activity and long-term stability under the actual working condition reaction temperature conditions.

[0004] To solve the above technical problems, the technical solution adopted by the present invention is as follows:

[0005] In the first aspect, the present invention provides a manganese-doped modified non-noble metal-based hydroxide oxygen evolution electrocatalyst, which is composed of a manganese-doped modified non-noble metal hydroxide active phase and a conductive substrate, and the manganese-doped modified non-noble metal hydroxide active phase is loaded on the surface of the conductive substrate in a nanostructure form.

[0006] The non-noble metals in the manganese-doped modified non-noble metal-based hydroxide active phase include one or more of Fe, Co, and Ni.

[0007] The overall structure of the manganese-doped modified non-noble metal-based hydroxide oxygen evolution electrocatalyst includes foamy, reticular, plate-like, lamellar, and rod-like shapes.

[0008] The conductive substrate includes foam metal, carbon paper, or carbon cloth. The thickness of the foam metal is 1.0 - 2.0 mm, and the porosity is 20 - 99%; the thickness of the carbon paper is 0.1 - 0.3 mm, and the porosity is 20 - 99%.

[0009] In a second aspect, the present invention provides a method for preparing a manganese-doped modified non-noble metal-based hydroxide oxygen evolution electrocatalyst, including the following steps:

[0010] Step a: Ultrasonically clean the conductive substrate with acid, deionized water, and ethanol respectively, and place it in a reaction kettle for standby;

[0011] Step b: Dissolve 2,5-dicarboxyterephthalic acid and transition metal salts in N,N-dimethylformamide to prepare a precursor solution through reaction;

[0012] Step c: Pour the precursor solution into the reaction kettle and react with the conductive substrate to grow a nanostructured non-noble metal hydroxide active phase on the surface of the conductive substrate, obtaining a non-noble metal-based hydroxide oxygen evolution electrocatalyst;

[0013] Step d: First place the non-noble metal-based hydroxide oxygen evolution electrocatalyst in the reaction kettle, then dissolve manganese metal salts in methanol and add them to the reaction kettle. After a solvothermal reaction, a manganese-doped modified non-noble metal-based hydroxide oxygen evolution electrocatalyst is obtained.

[0014] The present invention modifies the non-noble metal-based electrocatalyst by doping with manganese elements, which can reduce the binding energy between reaction intermediates and the surface active sites of the catalyst in the chemical water splitting oxygen evolution reaction, thereby improving the intrinsic activity of the catalyst for electrocatalytic oxygen evolution reaction.

[0015] In step a, the acid used to treat the conductive substrate includes nitric acid, sulfuric acid, hydrochloric acid, or hydrofluoric acid.

[0016] In step b, the dosage of 2,5-dicarboxyterephthalic acid is 0.1 - 1 mmol, the transition metal salts include one or more of iron salts, cobalt salts, or nickel salts, and the dosage is 0.3 - 5 mmol. The dosage of N,N-dimethylformamide is 20 - 300 mL.

[0017] In step c, the reaction temperature between the precursor solution and the conductive substrate is 120 - 180 o °C, and the time is 10 - 40 h.

[0018] In step d, the dosage of methanol is 50 - 300 mL; the reaction temperature of the solvothermal reaction is 100 - 250o C, with the time being 3 - 5 h.

[0019] In a third aspect, the present invention provides an application of a manganese - doped modified non - noble metal - based hydroxide oxygen evolution electrocatalyst in the electrolytic water decomposition for hydrogen production.

[0020] Advantages of the present invention: The present invention provides a manganese - doped modified non - noble metal - based hydroxide oxygen evolution electrocatalyst, its preparation method and application. First, the non - noble metal - based hydroxide oxygen evolution electrocatalyst is placed in a reaction kettle, and then a manganese metal salt is dissolved in methanol and added to the reaction kettle. After a solvothermal reaction, a manganese - doped modified non - noble metal - based hydroxide oxygen evolution electrocatalyst is obtained. Due to the low boiling point of the organic solvent, the solvothermal method adopted in the present invention can reach a higher air pressure under the same conditions compared with the hydrothermal method. The obtained samples have characteristics such as fine powder (nanoscale), high purity, good dispersibility, uniformity, no agglomeration, good crystal form, controllable shape, and being conducive to environmental purification, and are suitable for industrial production applications. In addition, compared with the high - temperature calcination method, the calcination step is omitted, and thus the grinding step is also omitted; when the manganese metal salt is dissolved in methanol and added to the reaction kettle, a doping regulation strategy is introduced, and transition metal ions can be introduced into the catalyst lattice, generating a large amount of lattice oxygen on the surface of the catalyst. This lattice oxygen can change the electron coordination environment, thereby regulating the electronic structure of the catalyst, affecting the electronic energy level of the catalyst, generating faster electron transfer and higher reaction activity. At the same time, doping can also regulate the adsorption energy of reactants on the active sites of transition metal hydroxides, helping to more effectively adsorb and catalytically react with reaction molecules to promote the oxygen evolution reaction activity, and maintaining high activity and long - term stability under the actual working condition reaction temperature. Description of the Drawings

[0021] Figure 1 Scanning electron microscope morphology diagram of the MnNiFe(OH)2 / NF (Fe:Mn = 1:1) catalyst prepared in Example 1 of the present invention;

[0022] Figure 2 High - resolution transmission electron microscope photograph of the MnNiFe(OH)2 / NF catalyst prepared in Example 1 of the present invention;

[0023] Figure 3 Comparison diagram of oxygen evolution reaction polarization curves of the MnNiFe(OH)2 / NF catalyst prepared in Example 1 of the present invention, the comparative samples NiFe(OH)2 / NF, pure NF, and RuO2 at room temperature;

[0024] Figure 4 Oxygen evolution reaction polarization curve diagram of the MnNiFe(OH)2 / NF catalyst prepared in Example 1 of the present invention at different temperatures;

[0025] Figure 5Comparison chart of the electrochemically active surface area test results of the MnNiFe(OH)2 / NF catalyst prepared in Example 1 of the present invention and the comparative sample NiFe(OH)2 / NF;

[0026] Figure 6 Stability test result chart of the MnNiFe(OH)2 / NF catalyst prepared in Example 1 of the present invention;

[0027] Figure 7 Oxygen evolution reaction polarization curve of the MnNiFe(OH)2 / NF (Fe:Mn = 1:3) catalyst prepared in Example 2 of the present invention at room temperature;

[0028] Figure 8 Oxygen evolution reaction polarization curve of the MnNiFe(OH)2 / NF (Fe:Mn = 3:1) catalyst prepared in Example 2 of the present invention at room temperature. Detailed implementation mode

[0029] The present invention will be further described below. The following examples are only used to more clearly illustrate the technical solution of the present invention and cannot be used to limit the protection scope of the present invention.

[0030] Example 1

[0031] The present invention provides a preparation method of a manganese-doped modified non-precious metal-based hydroxide oxygen evolution electrocatalyst (the molar ratio of iron and manganese in the feed is 1:1), including the following steps:

[0032] Step 1: Cut the nickel foam into pieces of 3 cm × 4 cm, ultrasonically clean them with hydrochloric acid, deionized water and ethanol respectively, and place them in a polytetrafluoroethylene reaction kettle for standby.

[0033] Step 2: Weigh 2,5-dicarboxyterephthalic acid (0.45 mmol), nickel chloride hexahydrate (0.72 mmol) and iron acetate (0.24 mmol), dissolve them in N,N-dimethylformamide (30 mL) to prepare a reaction precursor solution.

[0034] Step 3: Pour the above precursor solution into the reaction kettle, heat it to 120 °C for a solvothermal reaction for 24 h, and grow a nanostructured nickel-iron hydroxide (NiFe(OH)2) oxygen evolution electrocatalyst on the surface of the nickel foam. The Ni and Fe atom ratios in the actually obtained NiFe(OH)2 need to be determined by further characterization.

[0035] Step 4: Place the obtained NiFe(OH)2 / NF oxygen evolution electrocatalyst (NF represents nickel foam metal) in a polytetrafluoroethylene reaction kettle. Weigh 0.24 mmol of manganese chloride tetrahydrate and dissolve it in 25 mL of methanol to prepare a manganese chloride methanol solution. Then pour the manganese chloride methanol solution into the above-mentioned polytetrafluoroethylene reaction kettle containing the NiFe(OH)2 / NF oxygen evolution electrocatalyst and heat it to 130 o °C for a constant-temperature solvothermal reaction for 4 h to obtain the manganese-doped modified nickel-iron hydroxide oxygen evolution electrocatalyst.

[0036] The scanning electron microscope image of the manganese-nickel-iron ternary metal hydroxide oxygen evolution electrocatalyst obtained in Example 1 is as Figure 1 shown. The high-resolution transmission electron microscope photograph of the manganese-nickel-iron ternary metal hydroxide oxygen evolution electrocatalyst is as Figure 2 shown. According to HRTEM analysis, the corresponding phase of the manganese-nickel-iron ternary metal hydroxide oxygen evolution electrocatalyst is Ni(OH)2, and the interplanar spacing has increased, indicating that iron ions and manganese ions have been successfully doped into the Ni(OH)2 lattice. Then, the manganese-nickel-iron ternary metal hydroxide oxygen evolution electrocatalyst prepared by the present invention is subjected to an oxygen evolution activity test. The oxygen evolution activity test conditions are as follows: using (30 o °C to 70 o °C) 1.0 mol·L −1 −1 KOH as the oxygen evolution electrolyte. The test adopts a three-electrode system, with a platinum sheet as the counter electrode with a purity higher than 99.99%, and a saturated Ag / AgCl as the reference electrode. All test voltage values are calibrated to the voltage value of the standard hydrogen electrode. As Figure 3 can be seen, at a current density of 100 mA / cm 2 2, the overpotential for catalytic oxygen evolution reaction is 350 mV, which is superior to the oxygen evolution performance of Comparative Example 1, pure nickel foam metal, and ruthenium oxide samples. Figure 4 shows the oxygen evolution performance of Example 1 in different electrolyte test temperature environments, indicating that the sample can maintain its excellent performance in an alkaline high-temperature environment and is suitable for industrial electrolysis temperature environments. To evaluate the electrochemically active area, by fitting the current density and the scan rate, the Mn-doped NiFe-LDH / NF exhibits a C -2 value of 11.00 mF cm dl −2, which is greater than that of NiFe-LDH / NF (7.93 mF cm -2). The increase in the double-layer capacitance value of the MnNiFe-LDH sample indicates that it has more active sites, enhancing the ability of the electrolyte to penetrate into the internal structure of the material, thereby promoting the improvement of the electrocatalytic water oxidation reaction activity. As shown in Figure 6, after a 40 h stability test in 1 M potassium hydroxide solution, the current density did not significantly decay, indicating its good durability.

[0037] Comparative Example 1

[0038] This comparative example discloses a preparation method of an oxygen evolution electrocatalyst of nickel iron hydroxide without manganese doping by a solvothermal method, including the following steps:

[0039] Step 1: Cut the nickel foam into pieces of 3 cm × 4 cm, ultrasonically clean them with hydrochloric acid, deionized water, and ethanol respectively, and place them in a polytetrafluoroethylene reaction kettle for standby.

[0040] Step 2: Weigh 2,5-dicarboxyterephthalic acid (0.45 mmol), nickel chloride hexahydrate (0.72 mmol), and iron acetate (0.24 mmol), dissolve them in N,N-dimethylformamide (30 mL) to prepare a reaction precursor solution.

[0041] Step 3: Pour the above precursor solution into the reaction kettle, heat it to 130 o °C for a solvothermal reaction for 24 h to obtain the catalyst of Comparative Example 1 without manganese doping. It can be Figure 3 seen that at a current density of 100 mA / cm 2 , the overpotential of the catalyst without manganese doping for the oxygen evolution reaction is 410 mV. Among them, the oxygen evolution overpotentials at 100 mA cm -2 are: MnNiFe-LDH / NF: 340 mV, NiFe-LDH / NF: 410 mV, RuO2: 430 mV, NF: 520 mV.

[0042] Example 2

[0043] The present invention provides a preparation method of a manganese-doped modified non-noble metal-based hydroxide oxygen evolution electrocatalyst (the molar ratio of iron to manganese in the feed is 1:3), including the following steps:

[0044] Step 1: Cut the nickel foam into pieces of 3 cm × 4 cm, ultrasonically clean them with hydrochloric acid, deionized water, and ethanol respectively, and place them in a polytetrafluoroethylene reaction kettle for standby.

[0045] Step 2: Weigh 2,5-dicarboxyterephthalic acid (0.45 mmol), nickel chloride hexahydrate (0.72 mmol), and iron acetate (0.24 mmol), and dissolve them in N,N-dimethylformamide (30 mL) to prepare a reaction precursor solution.

[0046] Step 3: Pour the above precursor solution into a reaction kettle and heat it to 120 o °C for 24 h of solvothermal reaction to grow a nanostructured nickel-iron hydroxide (NiFe(OH)2) oxygen evolution electrocatalyst on the surface of nickel foam.

[0047] Step 4: Place the obtained NiFe(OH)2 / NF oxygen evolution electrocatalyst in a polytetrafluoroethylene reaction kettle. Weigh 0.72 mmol of manganese chloride tetrahydrate, dissolve it in 25 mL of methanol to prepare a manganese chloride methanol solution, and then pour the manganese chloride methanol solution into the above polytetrafluoroethylene reaction kettle containing the NiFe(OH)2 / NF oxygen evolution electrocatalyst. Heat it to 130 o °C for 4 h of constant-temperature solvothermal reaction to obtain the manganese-doped modified nickel-iron hydroxide oxygen evolution electrocatalyst. As Figure 7 known, the overpotential for the oxygen evolution reaction under a current density of 100 mA / cm 2 is 387 mV.

[0048] Example 3

[0049] The present invention provides a preparation method of a manganese-doped modified non-noble metal-based hydroxide oxygen evolution electrocatalyst (the molar ratio of iron to manganese in the feed is 3:1), which includes the following steps:

[0050] Step 1: Cut nickel foam into pieces of 3 cm × 4 cm, ultrasonically clean them with hydrochloric acid, deionized water, and ethanol respectively, and place them in a polytetrafluoroethylene reaction kettle for standby.

[0051] Step 2: Weigh 2,5-dicarboxyterephthalic acid (0.45 mmol), nickel chloride hexahydrate (0.72 mmol), and iron acetate (0.24 mmol), and dissolve them in N,N-dimethylformamide (30 mL) to prepare a reaction precursor solution.

[0052] Step 3: Pour the above precursor solution into a reaction kettle and heat it to 120 o °C for 24 h of solvothermal reaction to grow a nanostructured nickel-iron hydroxide (NiFe(OH)2) oxygen evolution electrocatalyst on the surface of nickel foam.

[0053] Step 4: Place the obtained NiFe(OH)2 / NF oxygen evolution electrocatalyst in a polytetrafluoroethylene reaction kettle. Weigh 0.08 mmol of manganese chloride tetrahydrate, dissolve it in 25 mL of methanol to prepare a manganese chloride methanol solution, and then pour the manganese chloride methanol solution into the above polytetrafluoroethylene reaction kettle containing the NiFe(OH)2 / NF oxygen evolution electrocatalyst, and heat it to 130 o °C for a constant-temperature solvothermal reaction for 4 h to obtain the manganese-doped modified nickel-iron hydroxide oxygen evolution electrocatalyst. As Figure 8 known, the overpotential for catalyzing the oxygen evolution reaction at a current density of 100 mA / cm 2 is 383 mV.

[0054] The above are only the preferred embodiments of the present invention. It should be pointed out that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A manganese-doped modified non-noble metal-based hydroxide oxygen evolution electrocatalyst, characterized in that: The hydroxide oxygen evolution electrocatalyst is composed of a manganese-doped modified non-precious metal hydroxide active phase and a conductive substrate, and the manganese-doped modified non-precious metal hydroxide active phase is loaded on the surface of the conductive substrate in a nanostructured form.

2. The manganese-doped modified non-noble metal-based hydroxide oxygen evolution electrocatalyst according to claim 1, wherein: The non-precious metal in the manganese-doped modified non-precious metal-based hydroxide active phase includes one or more of Fe, Co, and Ni.

3. The manganese-doped modified non-noble metal-based hydroxide oxygen evolution electrocatalyst according to claim 1, wherein: The overall structure of the manganese-doped modified non-precious metal-based hydroxide oxygen evolution electrocatalyst includes foam-like, net-like, plate-like, sheet-like, and rod-like.

4. The manganese-doped modified non-noble metal-based hydroxide oxygen evolution electrocatalyst according to claim 1, wherein: The conductive substrate includes foam metal, carbon paper, or carbon cloth. The thickness of the foam metal is 1.0 - 2.0 mm, and the porosity is 20 - 99%; the thickness of the carbon paper is 0.1 - 0.3 mm, and the porosity is 20 - 99%.

5. A preparation method of a manganese-doped modified non-noble metal-based hydroxide oxygen evolution electrocatalyst, characterized in that: It includes the following steps: Step a: After ultrasonic cleaning the conductive substrate with acid, deionized water, and ethanol respectively, place it in a reaction kettle for standby. Step b: Dissolve 2,5-dicarboxyterephthalic acid and transition metal salts in N,N-dimethylformamide to prepare a precursor solution through reaction. Step c: Pour the precursor solution into the reaction kettle and react with the conductive substrate to grow a nanostructured non-precious metal hydroxide active phase on the surface of the conductive substrate to obtain a non-precious metal-based hydroxide oxygen evolution electrocatalyst. Step d: First, place the non-precious metal-based hydroxide oxygen evolution electrocatalyst in a reaction kettle, then dissolve manganese metal salt in methanol and add it to the reaction kettle. After solvothermal reaction, a manganese-doped modified non-precious metal-based hydroxide oxygen evolution electrocatalyst is obtained.

6. The preparation method of the manganese-doped modified non-noble metal-based hydroxide oxygen evolution electrocatalyst according to claim 5, characterized in that: In step a, the acid used to treat the conductive substrate includes nitric acid, sulfuric acid, hydrochloric acid, or hydrofluoric acid.

7. The preparation method of the manganese-doped modified non-noble metal-based hydroxide oxygen evolution electrocatalyst according to claim 5, characterized in that: In step b, the dosage of 2,5-dicarboxyterephthalic acid is 0.1 - 1 mmol, the transition metal salts include one or more of iron salts, cobalt salts, or nickel salts, and the dosage is 0.3 - 5 mmol, and the dosage of N,N-dimethylformamide is 20 - 300 mL.

8. The preparation method of the manganese-doped modified non-noble metal-based hydroxide oxygen evolution electrocatalyst according to claim 5, characterized in that: In step c, the reaction temperature of the precursor solution and the conductive substrate is 120 to 180 o °C, and the time is 10 to 40 h.

9. The preparation method of the manganese-doped modified non-noble metal-based hydroxide oxygen evolution electrocatalyst according to claim 5, characterized in that: In step d, the amount of methanol used is 50 - 300 mL; the reaction temperature of the solvothermal reaction is 100 - 250 o °C, and the time is 3 - 5 h.

10. Application of the manganese-doped modified non-precious metal-based hydroxide oxygen evolution electrocatalyst according to any one of claims 1 to 4 in the electrolytic water decomposition for hydrogen production.

Images