Preparation method of three-dimensional ferrocobalt metal oxide oxygen evolution catalyst

Abstract

The invention relates to a preparation method of a three-dimensional ferrocobalt metal oxide oxygen evolution catalyst. According to the method, foamed nickel is selected as a carrier, the foamed nickel is pretreated, a metal ion and ethanol mixed solution is evenly adsorbed to the surface of the foamed nickel, then open fire ignition is carried out, and a second-level self-limiting combustion process is carried out, so that metal ions form a ferrocobalt metal oxide material with a three-dimensional network structure in situ on the surface of the foamed nickel. The method is simple and easy to implement, a target product can be generated within second-level time, and the area of a foamed nickel matrix is adjusted according to needs, so that the three-dimensional ferrocobalt metal oxide catalyst is prepared on a large scale. The material obtained by the invention is used as an oxygen evolution anode catalyst, and the three-dimensional network-shaped ferrocobalt metal oxide oxygen evolution catalyst shows excellent electrochemical performance.

Description

Technical Field

[0001] The present invention belongs to the field of electrocatalysts, and specifically relates to the preparation of a three-dimensional cobalt-iron metal oxide oxygen evolution catalyst by a combustion method and application thereof. Background Art

[0002] With the increasing scarcity of traditional fossil energy and worsening environmental pollution, people's demand for new clean energy is constantly increasing.

[0003] Hydrogen production by water electrolysis is a green hydrogen production method, which consists of the cathode hydrogen evolution reaction (HER) and the anode oxygen evolution reaction (OER). Among them, OER is a slow four-electron transfer process with poor reaction kinetics, which is the key link restricting the overall water electrolysis efficiency. Therefore, finding an efficient OER electrocatalyst has become a research hotspot in recent years.

[0004] In the field of oxygen evolution catalysts, cobalt iron oxide oxygen evolution catalysts have shown good application potential due to their high catalytic activity and low cost. However, traditional cobalt iron oxides are mostly dispersed particles with small specific surface area, which is not conducive to gas diffusion and material transport. In their research, Zhang Lijuan et al. prepared cobalt iron oxide by hydrothermal method and calcination method. -2 The overpotential at a current density of 339 mV is 339 mV. Studies have shown that the preparation of cobalt-iron metal oxides with three-dimensional microstructures can improve the electron transport and material diffusion process. However, the preparation of three-dimensional cobalt-iron metal oxides faces problems such as difficulty in controlling the material morphology and complex preparation process.

[0005] At present, the most common methods for preparing cobalt-iron metal oxide oxygen evolution catalysts are hydrothermal method and template method. The hydrothermal method uses an appropriate amount of cobalt salt and iron salt to prepare a solution, react under high temperature and high pressure hydrothermal conditions to form a precipitate of cobalt-iron metal oxide catalyst. For example, Michele Bastianello (DOI: 10.1039 / c9ra06310b) et al. dissolved stoichiometric amounts of precursor metal salts and oxalic acid in a polytetrafluoroethylene solution with an iron concentration of 0.1 mol / L and a cobalt concentration of 0.05 mol / L. Additives were added to the solution. NaOH aqueous solution was added at a pH of 12-13 to induce the precipitation of precursor oxalates and hydroxides. The gasket was then sealed, heated at 135°C for 72 hours, and allowed to cool to room temperature. The obtained solid powder was purified by washing and centrifugation, and finally the nanoparticles were dried at 80°C to obtain a cobalt-iron metal oxide catalyst. The template method uses carbon as a template material, mixes cobalt salt and iron salt with the template material, and reacts under appropriate conditions, and obtains the cobalt-iron metal oxide material of the corresponding structure by removing the template. For example, Huang Yarong (DOI: 10.1016 / j.jelechem.2019.04.010) et al. impregnated the KIT-6-100 template in an ethanol solution containing a cobalt-iron ratio of 1:2, and stirred vigorously to ensure that the precursor solution and the template are fully mixed. After the solvent is completely evaporated at room temperature, the container is placed on a 50°C beating plate overnight. The powder is sintered at 500°C in air for 5 hours. After cooling to room temperature, the powder is transferred to a NaOH solution, the template is leached for 24 hours, washed with distilled water, and centrifuged several times to obtain a cobalt-iron metal oxide catalyst. The hydrothermal method requires specific conditions of high temperature and high pressure in the process of synthesizing the catalyst, and the reaction time is long, and it is difficult to control the morphology and structure. The template method is complicated to operate in the process of synthesizing the catalyst, and it limits the morphology and characteristics of the catalyst, which is not easy to mass produce. Summary of the invention

[0006] The present invention aims to solve the problems of low catalyst activity and poor stability caused by small specific surface area, poor electron transfer and material diffusion of existing granular cobalt-iron catalysts, and provides a method and application for preparing a three-dimensional cobalt-iron metal oxide oxygen evolution catalyst. The invention selects nickel foam as a carrier, and allows the metal ion ethanol solution to be uniformly adsorbed on the surface of the nickel foam by pre-treating the nickel foam, and then ignites it through an open flame, causing a self-limiting combustion process of seconds, so that the metal ions form a cobalt-iron metal oxide material with a three-dimensional network structure in situ on the surface of the nickel foam. The method is simple and easy to operate, and the target product can be generated within seconds, and the area of ​​the nickel foam matrix can be adjusted as needed, so as to prepare a three-dimensional cobalt-iron metal oxide catalyst in large quantities. The material obtained by the present invention is used as an oxygen evolution catalyst, and the cobalt-iron metal oxide oxygen evolution catalyst with a three-dimensional network shows excellent electrochemical properties.

[0007] The technical solution of the present invention is as follows: A method for preparing a three-dimensional cobalt-iron metal oxide oxygen evolution catalyst, the method comprising the following steps: Step 1: Pretreatment of nickel foam The nickel foam is immersed in acetone for ultrasonic treatment, then cleaned with deionized water, then ultrasonicated with anhydrous ethanol and hydrochloric acid in sequence, and finally rinsed with anhydrous ethanol and dried for later use; The ultrasonic time of the acetone, anhydrous ethanol and hydrochloric acid is 10 to 120 min; The concentration of hydrochloric acid is 1~3 mol / L.

[0008] Step 2: Preparation of three-dimensional cobalt-iron metal oxide oxygen evolution catalyst Dissolve cobalt nitrate hexahydrate and ferric nitrate nonahydrate in anhydrous ethanol to obtain a mixed solution of metal salts, and then disperse them by ultrasonication; then immerse the nickel foam prepared in step one in the mixed solution of metal salts, and disperse them by ultrasonication again; finally, take out the immersed sample, ignite it in a ventilated environment, and fully burn it for 1 to 10 seconds until it is extinguished to obtain a three-dimensional cobalt-iron metal oxide oxygen evolution catalyst.

[0009] Among them, 50 mmol / L ~ 150 mmol / L cobalt nitrate and 50 mmol / L ~ 150mmol / L ferric nitrate are added to each liter of anhydrous ethanol.

[0010] The ultrasonic treatment time of the metal salt mixed solution and the metal salt mixed solution immersed in nickel foam was 10-120 min.

[0011] The three-dimensional cobalt-iron metal oxide oxygen evolution catalyst prepared by the method is used as an anode catalyst in the oxygen evolution reaction.

[0012] In the oxygen evolution reaction, in a three-electrode system, the three-dimensional cobalt-iron metal oxide oxygen evolution catalyst is the working electrode, the counter electrode is a platinum electrode, the reference electrode is a mercury oxide electrode, and the electrolyte is an O2-saturated 1 mol / L KOH solution.

[0013] The essential features of the present invention are: The present invention uses nickel foam as a carrier and prepares a three-dimensional cobalt-iron metal oxide oxygen evolution catalyst by a combustion method, which can achieve uniform distribution of three-dimensional network-like nano metal oxides on the nickel foam carrier to form an efficient catalyst structure. The combustion method has a simple preparation process and low cost, and has the characteristics of strong controllability, and can achieve precise regulation of the catalyst structure and performance. The oxygen evolution catalyst prepared by this method has high activity, stability and cycle performance, is suitable for water decomposition, oxygen reduction and other fields, and has broad application prospects.

[0014] The present invention has the following beneficial effects: 1. The combustion method used in the present invention is a simple and efficient preparation method, which is easy to operate, low in cost, can quickly obtain experimental results, has strong repeatability, is suitable for large-scale production, and is conducive to reducing costs. Catalysts of different specifications can be effectively prepared.

[0015] 2. The nickel foam matrix used in the present invention has good electrical conductivity and three-dimensional microstructure, which is beneficial to electron transfer and material diffusion, and improves the electrocatalytic performance of the oxygen evolution catalyst.

[0016] 3. Due to the good conductivity and three-dimensional microstructure of the material, the catalyst is in full contact with the electrolyte, the active sites are fully exposed, and the catalytic performance is excellent. -2 The overpotential is 253~274 mV at the current density, and it can operate stably.

[0017] In summary, the method of using nickel foam as a carrier, introducing anhydrous ethanol to dissolve metal salts, and preparing metal oxide oxygen evolution catalysts by combustion method has the advantages of high efficiency, simplicity, and excellent performance of the obtained products. It is helpful to promote the development of the field of oxygen evolution catalysts and promote the application and promotion of related technologies. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 is a scanning electron microscope photograph of the metal oxide catalyst prepared in Example 1 with a cobalt-iron molar ratio of 1:1; Figure 2 This is the polarization curve of the electrocatalytic OER reaction of the metal oxide with a cobalt-iron molar ratio of 1:1 prepared in Example 1.

[0019] Figure 3 is a scanning electron microscope photograph of the metal oxide catalyst prepared in Example 2 with a cobalt-iron molar ratio of 3:1; Figure 4 This is the polarization curve of the electrocatalytic OER reaction of the metal oxide with a cobalt-iron molar ratio of 3:1 prepared in Example 2.

[0020] Figure 5 is a scanning electron microscope photograph of the metal oxide catalyst prepared in Example 3 with a cobalt-iron molar ratio of 1:3; Figure 6 This is the polarization curve of the electrocatalytic OER reaction of the metal oxide with a cobalt-iron molar ratio of 1:3 prepared in Example 3. DETAILED DESCRIPTION

[0021] The present invention is further described below by way of examples, but is not limited to the examples. The experimental methods in the examples without specifying specific conditions are usually carried out according to conventional conditions and conditions described in the manual, or according to conditions recommended by the manufacturer. The general equipment, materials, reagents, etc. used can be obtained from commercial sources unless otherwise specified. The raw materials required for the following examples are all commercially available.

[0022] Example 1 The preparation method of CoFe metal oxide oxygen evolution catalyst comprises the following steps: Step 1: Preparation of nickel foam carrier: Cut the nickel foam into a rectangle of 1 cm*2 cm, and then cut off a corner of 1 cm*0.5 cm. Put the nickel foam into a beaker and first use an appropriate amount of acetone for ultrasonic treatment for 30 min, rinse the residual acetone with deionized water, then use anhydrous ethanol for ultrasonic treatment for 30 min, then use 3 mol / L hydrochloric acid for ultrasonic treatment for 30 min, and finally rinse with anhydrous ethanol and dry for use.

[0023] Step 2: Preparation of CoFe metal oxide oxygen evolution catalyst: 0.2183 g of cobalt nitrate hexahydrate and 0.3030 g of ferric nitrate nonahydrate were weighed and dissolved in 5 ml of anhydrous ethanol, and ultrasonicated at room temperature for 30 min to form an ethanol mixed solution of 150 mmol / L cobalt nitrate and 150 mmol / L ferric nitrate. Then the prepared nickel foam was immersed in the mixed solution, and the immersed sample was taken out and ignited under dry and ventilated conditions. It burned fully for 5 seconds and then extinguished itself, and then naturally cooled to room temperature to obtain a CoFe metal oxygen evolution catalyst.

[0024] The obtained CoFe metal oxygen evolution catalyst was tested for oxygen evolution reaction (OER) performance in an O2-saturated 1 mol / L KOH solution using an Ivium electrochemical workstation in the Netherlands, where the working electrode was a CoFe metal oxide oxygen evolution catalyst, the counter electrode was a 1*1 cm platinum sheet electrode, and the reference electrode was a mercury oxide electrode.

[0025] Figure 1 It can be seen that the CoFe metal oxide oxygen evolution catalyst presents a three-dimensional network connected structure.

[0026] Figure 2 It can be seen that the CoFe metal oxide oxygen evolution catalyst has a high current density of 100 mA cm -2 The overpotential is only 253 mV, which shows good catalytic performance.

[0027] Example 2 The preparation method of Co3Fe metal oxide oxygen evolution catalyst comprises the following steps: Step 1: Pretreatment of nickel foam: Cut the nickel foam into a rectangle of 1 cm*2 cm, and then cut off a corner of 1 cm*0.5 cm. Put the nickel foam into a beaker and first use an appropriate amount of acetone for ultrasonic treatment for 30 min, rinse the residual acetone with deionized water, then use anhydrous ethanol for ultrasonic treatment for 30 min, then use 3 mol / L hydrochloric acid for ultrasonic treatment for 30 min, and finally rinse with anhydrous ethanol and dry for use.

[0028] Step 2: Preparation of Co3Fe metal oxide oxygen evolution catalyst: 0.2183 g of cobalt nitrate hexahydrate and 0.1010 g of ferric nitrate nonahydrate were weighed and dissolved in 5 ml of anhydrous ethanol, and ultrasonicated at room temperature for 30 min to form an ethanol mixed solution of 150 mmol / L cobalt nitrate and 50 mmol / L ferric nitrate. Then the prepared nickel foam was immersed in the mixed solution, and the immersed sample was taken out and ignited under dry and ventilated conditions, and burned fully until extinguished and then cooled naturally to room temperature to obtain a Co3Fe metal oxygen evolution catalyst.

[0029] The obtained Co3Fe metal oxygen evolution catalyst was tested for oxygen evolution reaction (OER) performance in an O2-saturated 1 mol / L KOH solution using an Ivium electrochemical workstation in the Netherlands, where the working electrode was a Co3Fe metal oxide oxygen evolution catalyst, the counter electrode was a 1*1 cm platinum sheet electrode, and the reference electrode was a mercury oxide electrode.

[0030] Figure 3 It can be seen that the Co3Fe metal oxide oxygen evolution catalyst presents a three-dimensional network connected structure.

[0031] Figure 4 It can be seen that the Co3Fe metal oxide oxygen evolution catalyst has a current density of 100 mA cm -2 The overpotential is only 274 mV, which shows good catalytic performance.

[0032] Example 3 The preparation method of CoFe3 metal oxide oxygen evolution catalyst comprises the following steps: Step 1: Pretreatment of nickel foam: Cut the nickel foam into a rectangle of 1 cm*2 cm, and then cut off a corner of 1 cm*0.5 cm. Put the nickel foam into a beaker and first use an appropriate amount of acetone for ultrasonic treatment for 30 min, rinse the residual acetone with deionized water, then use anhydrous ethanol for ultrasonic treatment for 30 min, then use 3 mol / L hydrochloric acid for ultrasonic treatment for 30 min, and finally rinse with anhydrous ethanol and dry for use.

[0033] Step 2: Preparation of CoFe3 metal oxide oxygen evolution catalyst: 0.0728 g of cobalt nitrate hexahydrate and 0.3030 g of ferric nitrate nonahydrate were weighed and dissolved in 5 ml of anhydrous ethanol, and ultrasonicated at room temperature for 30 min to form an ethanol mixed solution of 50 mmol / L cobalt nitrate and 150 mmol / L ferric nitrate. Then the prepared nickel foam was immersed in the mixed solution, and the immersed sample was taken out and ignited under dry and ventilated conditions, and burned fully until extinguished and then cooled naturally to room temperature to obtain a CoFe3 metal oxygen evolution catalyst.

[0034] The obtained CoFe3 metal oxygen evolution catalyst was tested for oxygen evolution reaction (OER) performance in an O2-saturated 1 mol / L KOH solution using an Ivium electrochemical workstation from the Netherlands, where the working electrode was a CoFe3 metal oxide oxygen evolution catalyst, the counter electrode was a 1*1 cm platinum sheet electrode, and the reference electrode was a mercury oxide electrode.

[0035] Figure 5 It can be seen that the CoFe3 metal oxide oxygen evolution catalyst presents a three-dimensional network connected structure.

[0036] Figure 6 It can be seen that the CoFe3 metal oxide oxygen evolution catalyst has a current density of 100 mA cm -2 The overpotential is only 262 mV, which shows good catalytic performance.

[0037] Matters not covered by the present invention are known technologies.

Claims

1. A method for preparing a three-dimensional cobalt-iron metal oxide oxygen evolution catalyst, characterized in that the method comprises the following steps: Step 1: Pretreatment of nickel foam: The nickel foam is immersed in acetone for ultrasonic treatment, then washed with deionized water, then ultrasonicated with anhydrous ethanol and hydrochloric acid in sequence, and finally rinsed with anhydrous ethanol and dried for later use; Step 2: Preparation of three-dimensional cobalt-iron metal oxide oxygen evolution catalyst: Dissolving cobalt nitrate hexahydrate and ferric nitrate nonahydrate in anhydrous ethanol to obtain a metal salt mixed solution, and then ultrasonically dispersing it; then immersing the nickel foam prepared in step 1 in the metal salt mixed solution, and ultrasonically dispersing it again, and finally taking out the immersed sample, igniting it in a ventilated environment, and burning it until it is extinguished, to obtain a three-dimensional cobalt-iron metal oxide oxygen evolution catalyst; Wherein, 50 mmol ~ 150 mmol of cobalt nitrate and 50 mmol ~ 150 mmol of ferric nitrate are added per liter of anhydrous ethanol.

2. The method for preparing the three-dimensional cobalt-iron metal oxide oxygen evolution catalyst according to claim 1, characterized in that The burning time is 1 to 10 seconds.

3. The method for preparing the three-dimensional cobalt-iron metal oxide oxygen evolution catalyst according to claim 1, The method is characterized in that the ultrasonic time of the acetone, anhydrous ethanol and hydrochloric acid in step 1 is 10 to 120 minutes; In step 2, the ultrasonic time of the metal salt mixed solution and the metal salt mixed solution immersed in nickel foam is 10-120 minutes.

4. The method for preparing a three-dimensional cobalt-iron metal oxide oxygen evolution catalyst as claimed in claim 1, characterized in that in step 1, the concentration of hydrochloric acid is 1 to 3 mol / L.

5. Use of the three-dimensional cobalt-iron metal oxide oxygen evolution catalyst prepared by the method of claim 1, characterized in that it is used as an anode catalyst in the oxygen evolution reaction.

6. The use according to claim 5, characterized in that In the oxygen evolution reaction, in a three-electrode system, the three-dimensional cobalt-iron metal oxide oxygen evolution catalyst is the working electrode, the counter electrode is a platinum electrode, the reference electrode is a mercury oxide electrode, and the electrolyte is an O2-saturated 1 mol / L KOH solution.

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