Preparation method and application of metal oxide heterojunction photocatalyst with high-speed electron transmission channel

Abstract

The present invention belongs to the technical field of photocatalytic material preparation, and discloses a preparation method and application of a metal oxide heterojunction photocatalyst with a high-speed electron transmission channel. The present invention uses a simple water bath physical mechanical stirring technology to perfectly combine two semiconductors with matching energy levels in a very short time by constructing a dense interface under mild reaction conditions. At the same time, the present invention perfectly inlays two oxides with flower morphology and leaf structure for the first time through interface connection, providing a high-speed transmission channel for photogenerated electrons in the photocatalytic reaction, and ultimately achieving an improvement in the photocatalytic CO2 reduction performance.

Description

Technical Field

[0001] The invention belongs to the technical field of photocatalytic material preparation, and relates to a preparation method and application of a metal oxide heterojunction photocatalyst with a high-speed electron transmission channel. Background Art

[0002] The rapid development of industrialization relies on huge energy supply, and inevitably brings about large-scale CO2 emissions. Therefore, mankind is also facing serious energy shortages and environmental crises. Because the driving force can be the inexhaustible sunlight in nature, the photocatalytic CO2 reduction reaction is considered to be a very promising strategy by effectively converting greenhouse gas CO2 into energy fuels and valuable platform compounds, and has also attracted extensive research by scientists. However, the biggest problem facing the development of the photocatalytic CO2 field is the low photoconversion efficiency and poor selectivity of traditional catalysts. Therefore, the design and synthesis of efficient photocatalysts and the modification of traditional catalysts are particularly important.

[0003] A heterojunction is an interface region formed by the contact of semiconductors with matching energy levels. The heterostructure construction strategy can not only effectively adjust the energy level structure to optimize the catalytic redox ability, but also improve the light absorption ability. The most important thing is to change the electron migration path through the construction of the interface to prevent the recombination of photogenerated electrons and holes. Generally, heterojunction photocatalysts have the advantages of high light collection rate, delayed electron-hole recombination and fast charge transfer. However, the contact interface between the two semiconductors is the key to improving the performance of heterojunction materials, and the formation of a tight interface is not easy. At present, the design and synthesis of heterojunction photocatalytic materials with excellent performance still requires researchers to make more efforts. Summary of the invention

[0004] The purpose of the present invention is to provide a method for preparing a metal oxide heterojunction photocatalyst with a high-speed electron transmission channel. The method combines two oxides with special morphologies by a simple oil bath technique, and provides a high-speed channel for electron transmission by constructing a tight interface. In view of the problem that photogenerated carriers are easy to recombine during the photocatalytic CO2 reduction reaction, the heterojunction is constructed to integrate the electron transfer path, promote efficient electron migration, reduce charge recombination, effectively improve the reaction kinetics, and enhance the activity of photocatalytic CO2 reduction.

[0005] The specific technical solutions of the present invention are as follows:

[0006] A method for preparing a metal oxide heterojunction photocatalyst having a high-speed electron transmission channel, the steps are as follows:

[0007] (1) Weighing a certain amount of 2-methylimidazole and cobalt nitrate hexahydrate, respectively, and dissolving them in deionized water, adding the fully dissolved 2-methylimidazole solution to the cobalt nitrate hexahydrate aqueous solution at a uniform speed with a rubber-tipped dropper, stirring continuously with a magnetic stirrer during the adding process, ultrasonically treating the mixed solution to make it uniformly dissolved, and then precipitating and centrifuging to obtain a bright purple precipitate, washing and drying, and finally obtaining a leaf-shaped ZIF-67;

[0008] (2) Weigh a certain amount of EDTA and sodium hydroxide, dissolve them in deionized water, stir with a magnetic stirrer to fully dissolve them, add a certain amount of copper acetate dihydrate and n-butanol in sequence, perform ultrasonic treatment to form a uniform solution, transfer it to a high-pressure reactor, place it in an oven for solvothermal reaction, cool it to room temperature after the reaction, perform centrifugal treatment, wash it with water and alcohol, and vacuum dry the obtained deep red substance to obtain Cu2O powder;

[0009] (3) Weigh the blade-shaped ZIF-67 prepared in step (1), dissolve it in deionized water with ultrasound, add a certain amount of Cu2O, treat it in an oil bath for a certain period of time, centrifuge it, wash it with water several times, and vacuum dry it to obtain a solid powder. The powder is placed in a muffle furnace and calcined at a certain heating rate to finally obtain a Co3O4 / Cu2O heterojunction material.

[0010] In step (1),

[0011] In the 2-methylimidazole solution, the dosage ratio of 2-methylimidazole to deionized water is 3.0-3.4 g: 80-100 mL;

[0012] In the aqueous solution of cobalt nitrate hexahydrate, the dosage ratio of cobalt nitrate hexahydrate to deionized water is 1.2-1.6 g: 80-100 mL;

[0013] The volume ratio of the 2-methylimidazole solution to the cobalt nitrate hexahydrate aqueous solution is 1:1.

[0014] In step (1), the ultrasonic treatment time is 25-30 minutes, the precipitation time is 5.5-6 hours, the washing reagent is methanol, the drying temperature is 60° C., and the drying time is 10-12 hours.

[0015] In step (2), the mass ratio of EDTA, sodium hydroxide and cupric acetate dihydrate is 4-4.5 g:1.8-2.0 g:0.5-0.7 g, and the volume ratio of deionized water to n-butanol is 35-42 mL:0.5-0.7 mL.

[0016] In step (2), the magnetic stirring and ultrasonic treatment time are both 3-5 minutes, the solvent thermal reaction temperature is 100-110° C., and the reaction time is 300 minutes; the vacuum drying temperature is 60° C., and the vacuum drying time is 10-12 hours.

[0017] In step (3), the usage ratio of ZIF-67 and Cu2O is 100 mg:5-15 mg.

[0018] In step (3), the oil bath treatment temperature is 40-45°C, and the oil bath time is 30-35min; the vacuum drying temperature is 60°C, and the vacuum drying time is 4-6h; the muffle furnace heating rate is 3°C / min, the calcination temperature is 300°C, and the calcination time is 120-240min.

[0019] The metal oxide heterojunction photocatalyst with a high-speed electron transmission channel prepared by the present invention is used for photocatalytic CO2 reduction reaction.

[0020] The advantages of the present invention are:

[0021] (1) The Co3O4 / Cu2O heterojunction material prepared by the present invention has both nanoflower and nanoleaf structures. The perfect inlay of the nanoflower and nanoleaf structures provides a more effective platform for efficient charge transmission;

[0022] (2) The heterogeneous structure of the present invention effectively optimizes the energy level structure of the catalyst and provides support for the occurrence of the photocatalytic CO2 reduction reaction;

[0023] (3) The construction of a tight interface in the Co3O4 / Cu2O heterojunction material of the present invention provides a high-speed channel for carrier transport in the catalytic reaction, effectively improving the reaction kinetics and further enhancing the photocatalytic activity of the catalyst. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is the XRD diagram of the Cu2O / Co3O4 heterojunction material prepared in the present invention.

[0025] Figure 2 This is the SEM image of the Cu2O / Co3O4 heterojunction material prepared in the present invention.

[0026] Figure 3 The photocatalytic CO2 reduction activity diagram of the Cu2O / Co3O4 heterojunction material and the monomer with different Cu2O addition amounts prepared by the present invention. DETAILED DESCRIPTION

[0027] Embodiment 1:

[0028] (1) Weigh 3.0 g of 2-methylimidazole and 1.2 g of cobalt nitrate hexahydrate and dissolve them in 80 mL of deionized water respectively. Add the fully dissolved 2-methylimidazole solution to the cobalt nitrate hexahydrate aqueous solution at a uniform speed with a rubber-tipped dropper. Stir continuously with a magnetic stirrer during the addition process. Ultrasonicate the mixed solution for 25 min until it is uniformly dissolved. Then, settle for 5.5 h, centrifuge to obtain a bright purple precipitate, wash it three times with a methanol solution, and place it in a 60°C oven for 10 h to finally obtain leaf-shaped ZIF-67.

[0029] (2) Weigh 4.0 g of EDTA and 1.8 g of sodium hydroxide, dissolve them in 35 mL of deionized water, stir with a magnetic stirrer for 3 min to fully dissolve them, add 0.5 g of copper acetate dihydrate and 0.5 mL of n-butanol in sequence, treat with ultrasound to form a uniform solution, transfer to a 100 mL high-pressure reactor, place in a 100 ° C oven for 300 min of solvothermal reaction, cool to room temperature after the reaction, centrifuge, wash with water and alcohol twice each, and dry the obtained dark red substance in a 60 ° C vacuum drying oven for 10 h to obtain Cu2O powder.

[0030] (3) Weigh 100 mg of the blade-shaped ZIF-67 prepared in (1), dissolve it in 30 mL of deionized water by ultrasonic, add 5 mg of Cu2O, place it in a 40°C oil bath for reaction for 30 min, centrifuge it, wash it with water several times, and vacuum dry it to obtain a solid powder. The powder is placed in a muffle furnace and calcined at 300°C for 120 min with a heating rate of 3°C / min. After cooling, the Co3O4 / Cu2O heterojunction material is finally obtained, which is named 5-Co3O4 / Cu2O.

[0031] Embodiment 2:

[0032] (1) Weigh 3.2 g of 2-methylimidazole and 1.4 g of cobalt nitrate hexahydrate and dissolve them in 80 mL of deionized water respectively. Add the fully dissolved 2-methylimidazole solution to the cobalt nitrate hexahydrate aqueous solution at a uniform speed with a rubber-tipped dropper. Stir continuously with a magnetic stirrer during the addition process. Ultrasonicate the mixed solution for 30 min until it is uniformly dissolved. Then, settle for 6 h and centrifuge to obtain a bright purple precipitate. Wash it three times with a methanol solution and place it in a 60°C oven for 10 h to finally obtain leaf-shaped ZIF-67.

[0033] (2) Weigh 4.2 g of EDTA and 2.0 g of sodium hydroxide, dissolve them in 40 mL of deionized water, stir with a magnetic stirrer for 3 min to fully dissolve them, add 0.6 g of copper acetate dihydrate and 0.6 mL of n-butanol in sequence, treat with ultrasound to form a uniform solution, transfer to a 100 mL high-pressure reactor, place in a 110° C. oven for 300 min of solvothermal reaction, cool to room temperature after the reaction, centrifuge, wash with water and alcohol twice each, and dry the obtained dark red substance in a 60° C. vacuum drying oven for 10 h to obtain Cu2O powder.

[0034] (3) Weigh 100 mg of the blade-shaped ZIF-67 prepared in (1), dissolve it in 30 mL of deionized water by ultrasonic, add 10 mg of Cu2O, place it in a 45°C oil bath for reaction for 40 min, centrifuge and wash it with water three times, and vacuum dry it to obtain a solid powder. The powder is placed in a muffle furnace and calcined at 300°C for 180 min with a heating rate of 3°C / min. After cooling, a Co3O4 / Cu2O heterojunction material is finally obtained, which is named 10-Co3O4 / Cu2O.

[0035] Embodiment 3:

[0036] (1) Weigh 3.4 g of 2-methylimidazole and 1.6 g of cobalt nitrate hexahydrate and dissolve them in 100 mL of deionized water respectively. Add the fully dissolved 2-methylimidazole solution to the cobalt nitrate hexahydrate aqueous solution at a uniform speed with a rubber-tipped dropper. Stir continuously with a magnetic stirrer during the addition process. Ultrasonicate the mixed solution for 30 min until it is uniformly dissolved. Then, settle for 6.0 h, centrifuge to obtain a bright purple precipitate, wash it three times with a methanol solution, and place it in a 60°C oven for 12 h to finally obtain leaf-shaped ZIF-67.

[0037] (2) Weigh 4.5 g of EDTA and 2.0 g of sodium hydroxide, dissolve them in 42 mL of deionized water, stir with a magnetic stirrer for 3 min to fully dissolve them, add 0.7 g of copper acetate dihydrate and 0.7 mL of n-butanol in sequence, treat with ultrasound to form a uniform solution, transfer to a 100 mL high-pressure reactor, place in a 100 °C oven for 300 min of solvothermal reaction, cool to room temperature after the reaction, centrifuge, wash with water and alcohol twice each, and dry the obtained dark red substance in a 60 °C vacuum drying oven for 12 h to obtain Cu2O powder.

[0038] (3) Weigh 100 mg of the blade-shaped ZIF-67 prepared in (1), dissolve it in 30 mL of deionized water by ultrasonic, add 15 mg of Cu2O, place it in a 40°C oil bath for reaction for 30 min, centrifuge and wash it with water three times, and vacuum dry it to obtain a solid powder. The powder is placed in a muffle furnace and calcined at 300°C for 120 min with a heating rate of 3°C / min. After cooling, a Co3O4 / Cu2O heterojunction material is finally obtained, which is named 15-Co3O4 / Cu2O.

[0039] Figure 1 The XRD diagram of the Cu2O / Co3O4 heterojunction material prepared by the present invention, the XRD diffraction peaks of the heterojunction material correspond to the characteristic peaks of the standard cards of the two monomer materials Cu2O and In2S3, respectively, proving the successful synthesis of the Cu2O / Co3O4 heterojunction material;

[0040] Figure 2 This is the SEM image of the Cu2O / Co3O4 heterojunction material prepared by the present invention, verifying the perfect coupling of the flower-like Cu2O and the flake Co3O4;

[0041] Figure 3 The photocatalytic CO2 reduction activity diagram of the Cu2O / Co3O4 heterojunction material and the monomer with different Cu2O addition amounts prepared by the present invention shows that the catalytic performance of the Cu2O / Co3O4 heterojunction material is significantly improved compared with the monomer.

Claims

1. A method for preparing a metal oxide heterojunction photocatalyst having a high-speed electron transmission channel, characterized in that: The specific steps are as follows: (1) Weighing a certain amount of 2-methylimidazole and cobalt nitrate hexahydrate, respectively, and dissolving them in deionized water, adding the fully dissolved 2-methylimidazole solution to the cobalt nitrate hexahydrate aqueous solution at a uniform speed with a rubber-tipped dropper, stirring continuously with a magnetic stirrer during the adding process, ultrasonically treating the mixed solution to make it uniformly dissolved, and then precipitating and centrifuging to obtain a bright purple precipitate, washing and drying, and finally obtaining a leaf-shaped ZIF-67; (2) Weigh a certain amount of EDTA and sodium hydroxide, dissolve them in deionized water, stir with a magnetic stirrer to fully dissolve them, add a certain amount of copper acetate dihydrate and n-butanol in sequence, perform ultrasonic treatment to form a uniform solution, transfer it to a high-pressure reactor, place it in an oven for solvothermal reaction, cool it to room temperature after the reaction, perform centrifugal treatment, wash it with water and alcohol, and vacuum dry the obtained deep red substance to obtain Cu2O powder; (3) Weighing the blade-shaped ZIF-67 prepared in step (1), ultrasonically dissolving it in deionized water, adding a certain amount of Cu2O, treating it in an oil bath at 40-45°C for 30-35 min, centrifuging it, washing it with water for multiple times, and vacuum drying it to obtain a solid powder; placing the powder in a muffle furnace at 300°C for 120-240 min at a certain heating rate to finally obtain a Co3O4 / Cu2O heterojunction material; Among them, the usage ratio of ZIF-67 and Cu2O is 100mg:5-15mg.

2. The preparation method according to claim 1, characterized in that In step (1), in the 2-methylimidazole solution, the dosage ratio of 2-methylimidazole to deionized water is 3.0-3.4 g: 80-100 mL; in the cobalt nitrate hexahydrate aqueous solution, the dosage ratio of cobalt nitrate hexahydrate to deionized water is 1.2-1.6 g: 80-100 mL; and the volume ratio of the 2-methylimidazole solution to the cobalt nitrate hexahydrate aqueous solution is 1:

1.

3. The preparation method according to claim 1, characterized in that: In step (1), the ultrasonic treatment time is 25-30 minutes, the precipitation time is 5.5-6 hours, the washing reagent is methanol, the drying temperature is 60° C., and the drying time is 10-12 hours.

4. The preparation method according to claim 1, characterized in that: In step (2), the mass ratio of EDTA, sodium hydroxide and cupric acetate dihydrate is 4-4.5 g:1.8-2.0 g:0.5-0.7 g, and the volume ratio of deionized water to n-butanol is 35-42 mL:0.5-0.7 mL.

5. The preparation method according to claim 1, characterized in that: In step (2), the magnetic stirring and ultrasonic treatment time are both 3-5 minutes, the solvent thermal reaction temperature is 100-110° C., and the reaction time is 300 minutes; the vacuum drying temperature is 60° C., and the vacuum drying time is 10-12 hours.

6. The preparation method according to claim 1, characterized in that: In step (3), the vacuum drying temperature is 60°C, the vacuum drying time is 4-6h, and the muffle furnace heating rate is 3°C / min.

7. Use of the metal oxide heterojunction photocatalyst having a high-speed electron transmission channel prepared by the preparation method according to any one of claims 1 to 6 for photocatalytic CO2 reduction reaction.

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