Preparation method and application of high-performance gel catalyst

Abstract

The application aims to provide a preparation method and application of a high-performance gel catalyst, and belongs to the technical field of energy conversion and utilization, and the preparation method comprises the following steps: (1) pretreating a substrate; (2) immersing the pretreated substrate in a gel precursor solution; (3) adding a prepared oxidant solution to the solution in step (2) to make the solution polymerize into a gel on the substrate; (4) washing and drying the prepared gel material in step (3) for standby; and (5) immersing the gel material in step (4) in a prepared metal salt solution, drying, and irradiating to obtain the catalyst of the application. The gel catalyst preparation method provided by the application is simple in operation, low in cost, suitable for large-scale production, and the catalyst has excellent electrocatalytic performance and outstanding application advantages in the important green energy conversion and utilization field of water electrolysis.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of energy conversion and utilization, and particularly relates to a preparation method and application of a high-performance gel catalyst. BACKGROUND

[0002] Hydrogen is an ideal green clean energy, however, most of the hydrogen is currently produced by steam reforming, gasification and other chemical processes from fossil fuels such as methane and coal. Fossil fuels are non-renewable and cause great harm to the environment during use. Using renewable energy to decompose water (such as water electrolysis) to produce hydrogen is a truly green and sustainable hydrogen production approach, and the research on water electrolysis hydrogen production technology has extremely important application value. The water electrolysis process is composed of two half-reactions: cathodic hydrogen evolution reaction (HER) and anodic oxygen evolution reaction (OER). Among them, the OER reaction is slow in reaction kinetics due to its four-electron transfer mechanism, and requires a high overpotential, which restricts the efficiency of the entire water electrolysis process. Therefore, developing low-cost, high-efficiency and stable catalysts is the key to promoting the development of water electrolysis technology.

[0003] Currently, Pt is the best commercial HER catalyst, and Ru and Ir oxides are the most advanced OER commercial catalysts, but the scarcity and high cost of noble metals seriously limit the industrial development of water electrolysis technology. Therefore, the development of non-noble metal catalysts has attracted great attention in the academic and industrial communities and has made remarkable research progress. Related catalysts mainly include carbon materials and transition metal materials, among which low-cost cobalt (Co) and nickel (Ni) compounds are considered to be the most effective OER catalyst materials to replace noble metals. However, many transition metal electrocatalysts have serious self-aggregation, poor conductivity and poor stability, one of the solutions is to disperse transition metals on conductive carriers. Traditional conductive carriers usually cannot well anchor metal particles, and in harsh electrochemical environments, they are prone to cause peeling, aggregation and dissolution of metal active components. Therefore, developing a high-porosity multi-dimensional interconnected conductive network is one of the important strategies to improve the activity and stability of non-noble metal electrocatalysts.

[0004] Gel materials are one of the most widely studied soft materials in the 21st century, with a large number of three-dimensional porous network structures, high composition adjustability, and easy synthesis and functionalization. Recently, as a unique platform material, it has appeared in various applications in the field of energy storage, showing special excellent performance. For example, the hierarchical porous structure of gel materials with low density and high specific surface area can accommodate different types of catalysts and provide more active sites; many conductive gel skeletons can act as conductive platforms to facilitate electron transfer and electrochemical reaction processes. More importantly, the composition of the gel and its derivatives can be adjusted, and the electronic structure of the catalyst can be customized by introducing functional dopants into the gel or gel derivative. In addition, the introduction of defect sites (oxygen vacancies) in the active components of the catalyst can significantly increase the catalytic activity, but the commonly used high-temperature annealing reduction method to manufacture oxygen vacancies often accompanies nanostructure deformation and severe aggregation, which can greatly reduce the effective surface area of the catalyst. At the same time, the reaction rate is high at high temperature, and it is difficult to fine-tune the oxygen vacancy concentration. Studies have found that when the energy of photons is comparable to the energy of chemical bonds, high-energy photons can break and rebuild some chemical bonds even at room temperature, thereby inducing the generation of stable nanocrystals rich in defects. SUMMARY

[0005] The purpose of the present application is to provide a preparation method and application of a high-performance gel catalyst. By growing a gel on a treated substrate, a gel material with a three-dimensional porous structure is obtained, and then a certain amount of metal is impregnated. At the same time, the non-equilibrium properties of light treatment are used to effectively produce more defects and high-activity metal species, and embed them into the gel material matrix, thereby avoiding the aggregation of metal species, increasing the active surface area of the catalyst, and improving its electrocatalytic activity and stability.

[0006] The present application adopts the following technical scheme:

[0007] A preparation method of a high-performance gel catalyst, comprising the following steps:

[0008] Firstly, the substrate is pretreated;

[0009] Secondly, the treated substrate is immersed in a mixed solution of gel precursor and crosslinking agent; the immersion time is 1-60 min;

[0010] Thirdly, an oxidizing agent solution is added to the mixed solution of the second step, so that the gel precursor is polymerized into a gel on the substrate; the polymerization time is 1-24 h;

[0011] Fourthly, the gel material obtained in the third step is washed and dried;

[0012] Fifthly, a metal salt solution is added dropwise to the gel material obtained in the fourth step, and dried to obtain a gel catalyst;

[0013] Step 6, the gel catalyst obtained in step 5 is irradiated with ultraviolet or visible light, and the irradiation time is 0.5-48h;

[0014] Step 7, the gel catalyst obtained in step 6 is washed with deionized water until neutral, and dried to obtain the high-performance gel catalyst.

[0015] Further, the substrate in step 1 includes any one of carbon paper, carbon cloth, nickel mesh, titanium mesh, copper mesh, foamed copper, foamed nickel, and titanium fiber cotton; and the pretreatment method is high-temperature calcination, acid washing, or a single or combined method of acetone and water washing.

[0016] Further, the pretreatment method in step 1 is high-temperature calcination, followed by acetone and water washing, the calcination temperature is 220-500°C, and the calcination time is 1-9h.

[0017] Further, the gel precursor in step 2 includes any one of pyrrole, aniline, acrylic acid, chitosan, and graphene oxide, the crosslinking agent is phytic acid, the molar ratio of the gel precursor to the crosslinking agent is 1:20-20:1, the solvent of the mixed solution includes one or a combination of water or alcohol, and the concentration of the mixed solution is 1-100 mmol / ml.

[0018] Further, the gel precursor in step 2 includes any one of pyrrole, aniline, or acrylic acid, and the solvent includes water or isopropanol, and the concentration of the mixed solution is 1-50 mmol / l.

[0019] Further, the oxidizing agent in step 3 includes any one of ammonium persulfate, hydrogen peroxide, ferric trichloride, copper chloride, copper sulfate, and potassium permanganate, the solvent of the oxidizing agent solution includes one or a combination of water or alcohol, and the concentration of the oxidizing agent solution is 50-500 mg / ml.

[0020] Further, the oxidizing agent includes ammonium persulfate, hydrogen peroxide, or ferric trichloride, and the solvent is water.

[0021] Further, the drying in step 4 is vacuum drying, the drying temperature is 30-80°C, and the drying time is 1-12h, preferably, the drying time is 3-12h.

[0022] Further, the metal salt in step 5 includes any one or a combination of metal mixtures of acetylacetone complex metal compounds, nitrates, and chlorides, the solvent of the metal salt solution includes any one or a combination of water, methanol, ethanol, and isopropanol, and the concentration of the metal salt solution is 0.01-1 mol / L.

[0023] Further, the acetylacetone coordination metal compound includes acetylacetone iron, acetylacetone cobalt or acetylacetone nickel; the nitrate includes iron nitrate, cobalt nitrate or nickel nitrate; the chloride includes iron chloride, cobalt chloride or nickel chloride.

[0024] Further, the combined metal mixture is a bimetallic mixture, and the molar ratio of any two metals is 1:9~9:1.

[0025] Further, the metal salt solution is an acetylacetone coordination metal compound, the solvent is a mixed solution of alcohol and water, and the concentration of the metal salt solution is 0.05~0.25mol / L.

[0026] Further, the wavelength range of the ultraviolet or visible light in the sixth step is 200~850nm, preferably, the wavelength range is 380~630nm, and the processing time is 1~24h.

[0027] A high-performance gel catalyst is applied to electrocatalytic overall water splitting and carbon dioxide reduction reactions.

[0028] The conductive gel network in the catalyst of the application not only can disperse and anchor metal active species, but also can realize fast electron transmission through effective diffusion path, and more effectively utilize active sites; the rich functional groups in the conductive gel can promote effective interaction between active species and gel materials, and inhibit the rapid phase change of metal active species in the water electrolysis process. At the same time, under the light-assisted treatment, the gel network morphology changes, effectively limits the migration and aggregation of metal species, and promotes the formation of more defects and high-activity metal species, enhances the hydrophilicity of the catalyst surface, and thus exhibits extremely excellent electrocatalytic performance in overall water splitting, carbon dioxide reduction and other reactions.

[0029] The beneficial effects of the application are as follows:

[0030] The preparation method of the application is simple, easy to operate and low in cost. The gel substrate prepared has a three-dimensional microstructure and high hydration, which means that it is beneficial to the interface interaction with the electrolyte and strengthens the charge transfer in the electrocatalytic process. In addition, the polypyrrole hydrogel also has high conductivity, strong structural stability, and strong ability to form a good interface with the electron transport phase (electrode) and ion transport phase (electrolyte). At the same time, under the light-assisted action, the gel network morphology changes, effectively limits the migration and aggregation of metal species, and promotes the formation of more defects and high-activity metal species, enhances the hydrophilicity of the catalyst surface, and thus exhibits extremely excellent electrocatalytic performance in overall water splitting, carbon dioxide reduction and other reactions. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1A scanning electron microscope (SEM) image of the high performance gel catalyst E2 prepared for the present embodiment 2;

[0032] Figure 2 A polarization curve graph of the high performance gel catalyst E2 prepared for the present embodiment 2 in the application of electrocatalytic overall water splitting;

[0033] Figure 3 A performance cycle stability graph of the high performance gel catalyst E2 prepared for the present embodiment 2 in the application of electrocatalytic water splitting oxygen evolution. DETAILED DESCRIPTION

[0034] In order to make the objects, technical solutions and advantages of the present application clearer, the present application will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and do not limit the present application.

[0035] Embodiment 1

[0036] Step 1: Pretreatment of carbon paper:

[0037] The carbon paper of the right size was calcined at 250°C and repeatedly washed with hydrochloric acid and deionized water, and dried in an oven at 60°C for standby use.

[0038] Step 2: 0.085 ml of pyrrole and phytic acid was dissolved in 1 ml of isopropyl alcohol to make the molar ratio of phytic acid and pyrrole 6, and ultrasonic dispersion was uniform, and the carbon paper treated in step (1) was immersed in the mixed solution of phytic acid and pyrrole; the immersion time was 30 min.

[0039] Step 3: 184 mg of ferric chloride was weighed and dissolved in 1 ml of aqueous solution, ultrasonic dispersion was uniform, and it was poured into the mixed solution of step 2, and polymerization was carried out for 3 h.

[0040] Step 4: The carbon paper with completed polymerization in step 3 was taken out, ultrasonic washing was carried out with isopropyl alcohol and water for 10 min respectively, and the obtained sample was placed in a vacuum oven and dried at 40°C for 10 h.

[0041] Step 5: 16 mg of cobalt acetylacetonate was weighed and dissolved in a mixed solution of methanol and water, ultrasonic dispersion was uniform, and an appropriate amount of cobalt acetylacetonate solution was added dropwise to the polypyrrole gel substrate obtained in step 4, so that the loading amount reached 0.1 mg·cm -2 .

[0042] Step 6: The sample obtained in step 5 was treated with a 420 nm light source for 6 h.

[0043] Step 7: The sample in step 6 was washed to neutral with water, dried in an oven at 60°C, and a high performance bimetallic gel catalyst E1 was obtained.

[0044] The high performance gel catalyst E1 obtained was used as the working electrode, mercury oxide as the reference electrode, and platinum sheet as the counter electrode to test the HER and OER performance in 1 M KOH. The results showed that the overpotential of the gel catalyst was as low as 275 mV at 10 mA.cm -2 and the catalytic activity could still be maintained after 10,000 cycles of CV.

[0045] Example 2

[0046] Step 1: Pretreatment of carbon paper

[0047] The carbon paper of proper size was calcined at 250°C and repeatedly washed with hydrochloric acid and deionized water, and dried in an oven at 60°C for standby use.

[0048] Step 2: 0.085 ml of pyrrole and phytic acid were dissolved in 1 ml of isopropyl alcohol to make the molar ratio of phytic acid to pyrrole 6, and ultrasonic dispersion was uniform, and the carbon paper treated in step (1) was immersed in the mixed solution of phytic acid and pyrrole; the immersion time was 30 min.

[0049] Step 3: 184 mg of ammonium persulfate was weighed and dissolved in 1 ml of aqueous solution, ultrasonic dispersion was uniform, and it was poured into the mixed solution of step 2, and polymerization was carried out for 3 h.

[0050] Step 4: The carbon paper with completed polymerization in step 3 was taken out, ultrasonic washing was carried out with isopropyl alcohol and water for 10 min respectively, and the obtained sample was placed in a vacuum oven and dried at 40°C for 10 h.

[0051] Step 5: 16 mg of cobalt acetylacetonate was dissolved in a mixed solution of methanol and water, ultrasonic dispersion was uniform, and an appropriate amount of cobalt acetylacetonate solution was added dropwise to the polypyrrole gel substrate obtained in step 4, so that the loading amount reached 0.1 mg.cm -2 .

[0052] Step 6: The sample obtained in step 5 was treated with a 420 nm light source for 6 h.

[0053] Step 7: The sample in step 6 was washed to neutral with water and dried in an oven at 60°C to obtain a high performance gel catalyst E2.

[0054] The high performance gel catalyst E2 obtained was used as the working electrode, mercury oxide as the reference electrode, and platinum sheet as the counter electrode to test the HER and OER performance in 1 M KOH. The results showed that the overpotential of the gel catalyst was as low as 200 mV at 10 mA.cm -2 and 100 mA.cm -2and still can keep its catalytic activity after 10000 CV cycles.

[0055] Example 3

[0056] Step 1: Pretreatment of carbon paper:

[0057] The carbon paper was cut to size, calcined at 250°C, and washed repeatedly with hydrochloric acid and deionized water, and dried in an oven at 60°C for standby use.

[0058] Step 2: 0.085 ml of pyrrole and phytic acid were dissolved in 1 ml of isopropyl alcohol to make the molar ratio of phytic acid to pyrrole 6, and ultrasonic dispersion was performed, and the carbon paper treated in step (1) was immersed in the mixed solution of phytic acid and pyrrole; the immersion time was 30 min.

[0059] Step 3: 184 mg of ammonium persulfate was weighed and dissolved in 1 ml of aqueous solution, ultrasonic dispersion was performed, and it was poured into the mixed solution of step 2, and polymerization was performed for 3 h.

[0060] Step 4: The carbon paper polymerized in step 3 was taken out, ultrasonic washing was performed with isopropyl alcohol and water for 10 min respectively, and the obtained sample was placed in a vacuum oven and dried at 40°C for 10 h.

[0061] Step 5: 16 mg of nickel acetylacetonate was weighed and dissolved in a mixed solution of methanol and water, ultrasonic dispersion was performed, and an appropriate amount of nickel acetylacetonate solution was added dropwise to the polypyrrole gel substrate obtained in step 4, so that the loading amount reached 0.1 mg·cm -2 .

[0062] Step 6: The sample obtained in step 5 was treated with a 420 nm light source for 6 h.

[0063] Step 7: The sample in step 6 was washed to neutral with water, dried in an oven at 60°C, and a high-performance gel catalyst E3 was obtained.

[0064] The obtained high-performance gel catalyst E3 was used as a working electrode, silver / silver chloride was used as a reference electrode, and platinum was used as a counter electrode, and a CO2 RR performance test was performed in a 0.5 M potassium bicarbonate solution. The results show that the faradic efficiency of the catalytic generation of CO can reach 80%.

[0065] Example 4

[0066] Step 1: Pretreatment of carbon paper:

[0067] The carbon paper was cut to size, calcined at 250°C, and washed repeatedly with hydrochloric acid and deionized water, and dried in an oven at 60°C for standby use.

[0068] Step 2: 0.085 ml of aniline and phytic acid were dissolved in 1 ml of isopropyl alcohol to make the molar ratio of phytic acid and aniline 6, and ultrasonic dispersion was performed to make them uniformly dispersed. The carbon paper treated in step (1) was immersed in the mixed solution of phytic acid and aniline; the immersion time was 30 min.

[0069] Step 3: 184 mg of ammonium persulfate was weighed and dissolved in 1 ml of water solution, ultrasonic dispersion was performed to make it uniformly dispersed, and it was poured into the mixed solution of step 2 to make it polymerize for 3 h.

[0070] Step 4: The carbon paper on which polymerization was completed in step 3 was taken out, ultrasonic cleaning was performed with isopropyl alcohol and water for 10 min respectively, and the obtained sample was placed in a vacuum oven and dried at 40°C for 10 h.

[0071] Step 5: 16 mg of cobalt acetylacetonate was weighed and dissolved in a mixed solution of methanol and water, ultrasonic dispersion was performed to make it uniformly dispersed, and an appropriate amount of cobalt acetylacetonate solution was added dropwise to the polyaniline gel substrate obtained in step 4 to make the loading amount reach 0.1 mg·cm -2 .

[0072] Step 6: The sample obtained in step 5 was treated with a light source of 420 nm for 6 h.

[0073] Step 7: The sample in step 6 was washed to neutral with water, and dried in an oven at 60°C to obtain a high-performance gel catalyst E4.

[0074] The obtained high-performance gel catalyst E4 was used as a working electrode, mercury oxide was used as a reference electrode, and a platinum sheet was used as a counter electrode, and HER and OER performance tests were performed in 1M KOH. The results show that the overpotential of the gel catalyst is as low as 312 mV at 10 mA·cm -2 , and the catalytic activity can still be maintained after 10,000 cycles of CV.

[0075] Example 5

[0076] Step 1: The foam nickel was pretreated:

[0077] The foam nickel with a proper size was repeatedly cleaned with acetone and deionized water, and dried in an oven at 60°C for standby use.

[0078] Step 2: 0.085 ml of aniline and phytic acid were dissolved in 1 ml of isopropyl alcohol to make the molar ratio of phytic acid and aniline 6, and ultrasonic dispersion was performed to make them uniformly dispersed. The carbon paper treated in step (1) was immersed in the mixed solution of phytic acid and aniline; the immersion time was 30 min.

[0079] Step 3: 184 mg of ammonium persulfate was weighed and dissolved in 1 ml of water solution, and was ultrasonically dispersed and quickly poured into the mixed solution of Step 2 to polymerize for 3 h.

[0080] Step 4: The polymerized foam nickel in Step 3 was taken out, ultrasonically cleaned with isopropanol and water for 10 min respectively, and the obtained sample was placed in a vacuum oven and dried at 40°C for 10 h.

[0081] Step 5: 48 mg of cobalt acetylacetonate was weighed and dissolved in a mixed solution of methanol and water, and was ultrasonically dispersed, and an appropriate amount of cobalt acetylacetonate solution was added dropwise to the polypyrrole gel substrate obtained in Step 4 to achieve a loading amount of 0.3 mg·cm -2 .

[0082] Step 6: The sample obtained in Step 5 was treated with a 420 nm light source for 6 h.

[0083] Step 7: The sample in Step 6 was washed to neutral with water, and was dried in an oven at 60°C to obtain a high-performance gel catalyst E5.

[0084] The obtained high-performance gel catalyst E5 was used as a working electrode, mercury oxide was used as a reference electrode, and a platinum sheet was used as a counter electrode, and HER and OER performance tests were carried out in 1M KOH. The results show that the overpotential of the gel catalyst is 283 mV at 10 mA·cm -2 , and the catalyst activity can still be maintained after 10,000 cycles of CV.

[0085] Figure 1 It is a scanning electron microscope (SEM) image of the high-performance gel catalyst E2 in Example 2 of the application. As can be seen from the figure, the polypyrrole gel grown on the carbon paper has a three-dimensional porous structure, which is conducive to the dispersion of the metal active component in the gel network.

[0086] Figure 2 It is a polarization curve of the high-performance gel catalyst E2 in Example 2 of the application in the application of electrocatalytic overall water splitting. As can be seen from the figure, a working voltage of only 0.632 V can achieve a hydrogen evolution and oxygen evolution current density of 10 mA·cm -2 , and a working voltage of 1.58 V can also make the hydrogen evolution and oxygen evolution current density reach 100 mA·cm -2 .

[0087] Figure 3 It is a cycle stability diagram of the high-performance gel catalyst E2 in Example 2 of the application in the application of electrocatalytic oxygen evolution. As can be seen from the figure, the catalyst has excellent stability within a test time of 20 h.

[0088] It is to be understood that the above-described embodiments are merely illustrative of the application and do not limit the scope of the application. Various modifications and changes can be made by those skilled in the art, which modifications and changes are also within the scope of the application as defined by the appended claims.

Claims

1. A process for the preparation of a high performance gel catalyst characterized by: The method comprises the following steps: In the first step, the substrate is pretreated; the substrate comprises any one of carbon paper, carbon cloth, nickel mesh, titanium mesh, copper mesh, foamed copper, foamed nickel, and titanium fiber cotton; the pretreatment method is high-temperature calcination, acid pickling, acetone and water cleaning, or a combination thereof; In the second step, the pretreated substrate is immersed in a mixed solution of a gel precursor and a cross-linking agent; the immersion time is 1-60 min; the gel precursor comprises any one of pyrrole and aniline; In the third step, an oxidizing agent solution is added to the mixed solution of the second step, so that the gel precursor is polymerized into a gel on the substrate; the polymerization time is 1-24 h; In the fourth step, the gel material obtained in the third step is washed and dried; In the fifth step, a metal salt solution is added dropwise to the gel material obtained in the fourth step, and the gel catalyst is obtained after drying; the metal salt comprises any one of an acetylacetone complex metal compound, a nitrate, and a chloride; The acetylacetone complex metal compound comprises cobalt acetylacetone or nickel acetylacetone; the nitrate comprises cobalt nitrate or nickel nitrate; and the chloride comprises cobalt chloride or nickel chloride; In the sixth step, the gel catalyst obtained in the fifth step is irradiated with ultraviolet or visible light, and the irradiation time is 0.5-48 h; In the seventh step, the gel catalyst obtained in the sixth step is washed with deionized water until it is neutral, and then dried to obtain the high-performance gel catalyst.

2. A process for the preparation of a high performance gel catalyst as claimed in claim 1, wherein: In the first step, the pretreatment method is high-temperature calcination, followed by acetone and water cleaning; the calcination temperature is 220-500°C, and the calcination time is 1-9 h.

3. A process for the preparation of a high performance gel catalyst as claimed in claim 1, wherein: In the second step, the cross-linking agent is phytic acid, the molar ratio of the gel precursor to the cross-linking agent is 1:20-20:1, and the solvent of the mixed solution comprises one or a combination of water or alcohol, and the concentration of the mixed solution is 1-100 mmol / ml.

4. The process for the preparation of high performance gel catalyst as claimed in claim 1, wherein: In the third step, the oxidizing agent comprises any one of ammonium persulfate, hydrogen peroxide, ferric trichloride, copper chloride, copper sulfate, and potassium permanganate; the solvent of the oxidizing agent solution comprises one or a combination of water or alcohol, and the concentration of the oxidizing agent solution is 50-500 mg / ml.

5. The process for the preparation of high performance gel catalyst as claimed in claim 1, wherein: In the fourth step, the drying is vacuum drying, the drying temperature is 30-80°C, and the drying time is 1-12 h.

6. The process for the preparation of high performance gel catalyst as claimed in claim 1, wherein: In the fifth step, the solvent of the metal salt solution comprises any one or a combination of water, methanol, ethanol, and isopropanol, and the concentration of the metal salt solution is 0.01-1 mol / L.

7. The process for the preparation of high performance gel catalyst as claimed in claim 1, wherein: In the sixth step, the wavelength range of the ultraviolet or visible light is 200-420 nm, and the treatment time is 1-24 h.

8. The high-performance gel catalyst prepared by the preparation method of claim 1 is applied to an electrocatalytic overall water splitting reaction.

Images