D-Co3O4 / CC electrocatalyst rich in oxygen vacancy defect, preparation method of D-Co3O4 / CC electrocatalyst and application of D-Co3O4 / CC electrocatalyst in urea wastewater degradation

Abstract

The invention discloses a D-Co3O4 / CC electrocatalyst material rich in oxygen vacancy defects, and particularly relates to the technical field of electrocatalysis, the electrocatalyst material takes carbon cloth as a substrate, and the surface of the carbon cloth is loaded with Co3O4 rich in oxygen vacancy defects. Meanwhile, the invention also provides a preparation method of the electro-catalytic material and application of the electro-catalytic material in urea wastewater degradation. The introduction of the oxygen-rich vacancy defect enables the D-Co3O4 to have a larger reaction active area and smaller mass transfer resistance. The D-Co3O4 / CC electrocatalyst material obtained by the preparation method disclosed by the invention shows high urea wastewater degradation efficiency and degradation stability.

Description

Technical Field

[0001] The present invention relates to the technical field of electrocatalysis, and in particular to a D-Co 3 O 4 / CC electrocatalyst and its preparation method and application. Background Art

[0002] Developing sustainable and environmentally friendly renewable energy conversion technologies is one of the effective ways to solve severe environmental problems. Hydrogen is a clean and green alternative to fossil fuels. When water electrolysis is used to produce hydrogen, hydrogen is produced at the cathode while oxygen is produced at the anode. The produced hydrogen and oxygen may mix and explode. In addition, the anodic oxygen evolution reaction (OER) of water electrolysis has a large driving voltage and high hydrogen production cost due to its complex four-electron transfer process. Therefore, replacing OER with other anode reactions with lower oxidation thermodynamic equilibrium voltage will make energy-saving hydrogen production possible. Replacing the OER reaction with the urea oxidation reaction, which has a lower thermodynamic equilibrium potential (0.37V relative to the reversible hydrogen electrode), can not only achieve low-energy hydrogen production, but also purify urea-rich wastewater.

[0003] Chlorine radicals (Cl·) can convert nitrogen compounds into N with high activity and selectivity. 2 Urea wastewater contains high concentrations of Cl - , in situ generation of Cl· via a single-electron pathway provides an alternative. Commonly used anodes are usually composed of noble metals (Ir and Ru), but their high cost hinders their application. 3 O 4 Due to its low cost and catalytic performance, it has attracted extensive attention in water splitting. 3 O 4 The structure of Co 3+ It has a high redox potential and can convert Cl - Activated to Cl·. However, Co 3 O 4 Co in oxide 2+ Oxidized to Co 3+ It is the rate-determining step of its catalytic activity. For metal oxides, oxygen vacancies can adjust the coordination structure and electronic state, thereby accelerating the kinetics of the catalytic process. However, Co 3 O 4 The role and mechanism of oxygen vacancy defects in producing Cl· in urea wastewater degradation are still unclear. Summary of the invention

[0004] For Co 3 O 4The present invention provides a D-CoO2-rich catalytic catalyst with oxygen vacancy defects to solve the problems of low catalytic activity rate of oxides and unclear mechanism of their interaction with oxygen vacancy defects in producing Cl· in urea wastewater degradation. 3 O 4 / CC electrocatalyst and its preparation method and application, the prepared composite catalyst has high urea wastewater degradation performance.

[0005] The present invention is achieved through the following technical solutions:

[0006] A D-Co with oxygen vacancy defects 3 O 4 / CC electrocatalyst material, characterized in that the catalyst comprises an array of pore-rich nanosheets grown on carbon cloth.

[0007] Furthermore, the oxygen vacancy defect-rich D-Co 3 O 4 / CC electrocatalyst material, characterized in that the thickness of the nanosheets in the electrocatalyst is 2-10nm and the size of the pores is 1-3nm.

[0008] A method for preparing the composite catalyst comprises:

[0009] S1. Dissolve cobalt salt in deionized water and immerse the carbon cloth in the above solution; dissolve dimethyl imidazole in deionized water and add it to the above solution for reaction. The obtained product is Co-MOF / CC after washing, centrifugation and drying; S2. Cut the Co-MOF / CC and immerse it in an ethanol solution containing cobalt salt for etching. The obtained sample is washed with ethanol and dried naturally in air to obtain Co(OH) 2 / CC.

[0010] S3, will get Co(OH) 2 / CC was annealed in air and cooled to room temperature in natural environment to obtain D-Co 3 O 4 / CC. Further, the cobalt salt described in S1 comprises cobalt chloride hexahydrate, and the cobalt salt described in S2 comprises cobalt chloride hexahydrate.

[0011] Furthermore, the mass ratio of the cobalt chloride hexahydrate to the dimethylimidazole is (0.8-1.5): (2-4). Furthermore, the reaction time described in S1 is 10-14 hours. The etching time described in S2 is 20-40 minutes. The calcination described in S3 is calcined at 250-450°C for 1.5-2.5 hours.

[0012] A D-Co with oxygen vacancy defects as described above 3 O 4 Application of CC electrocatalysts in electrocatalytic urea wastewater degradation.

[0013] Beneficial Effects

[0014] D-Co with oxygen vacancy defect prepared by the present invention 3 O 4 / CC electrocatalysts are simple to prepare, with abundant and inexpensive raw materials; D-Co 3 O 4 / CC electrocatalyst has excellent electrocatalytic urea wastewater degradation activity. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 The D-Co with oxygen vacancy defects prepared in Example 1 3 O 4 / SEM images of CC electrocatalysts;

[0016] Figure 2 The D-Co with oxygen vacancy defects prepared in Example 1 3 O 4 High-resolution transmission electron microscopy image of / CC electrocatalyst;

[0017] Figure 3 The D-Co with oxygen vacancy defects prepared in Example 1 3 O 4 / Electrocatalytic urea wastewater degradation performance of CC electrocatalyst;

[0018] Figure 4 The D-Co with oxygen vacancy defects prepared in Example 1 3 O 4 / CC electrocatalyst for urea wastewater degradation cyclic stability. DETAILED DESCRIPTION

[0019] In order to further understand the present invention, preferred embodiments of the present invention are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, rather than limiting the claims of the present invention.

[0020] Example 1

[0021] (1) Add an aqueous solution containing 2-methylimidazole (40 mL, 0.4 M) to CoCl 2 6H 2 O aqueous solution (40 mL, 0.05 M), and then the hydrophilic carbon cloth (CC) was immersed in the above mixed solution. After standing for 12 hours, it was washed with deionized water and vacuum dried to obtain Co-MOF / CC.

[0022] (2) The Co-MOF / CC obtained in step (1) was cut to a specific size and immersed in a solution containing CoCl2 6H 2 O (0.6 g) in an ethanol solution (100 mL) for 30 min. The sample was taken out, washed with ethanol and dried naturally in air to obtain Co(OH) 2 / CC.

[0023] (3) Co(OH) obtained in step (2) 2 The / CC sample was annealed in air at 350 °C for 2 h to obtain D-Co 3 O 4 / CC.

[0024] Example 2

[0025] (1) Add an aqueous solution containing 2-methylimidazole (40 mL, 0.4 M) to CoCl 2 6H 2 O aqueous solution (40 mL, 0.05 M), and then the hydrophilic carbon cloth (CC) was immersed in the above mixed solution. After standing for 10 hours, it was washed with deionized water and vacuum dried to obtain Co-MOF / CC.

[0026] (2) The Co-MOF / CC obtained in step (1) was cut to a specific size and immersed in a solution containing CoCl 2 6H 2 O (0.6 g) in an ethanol solution (100 mL) for 20 min. The sample was taken out, washed with ethanol and dried naturally in air to obtain Co(OH) 2 / CC.

[0027] (3) Co(OH) obtained in step (2) 2 The / CC sample was annealed in air at 250 °C for 2.5 h to obtain D-Co 3 O 4 / CC.

[0028] Example 3

[0029] (1) Add an aqueous solution containing 2-methylimidazole (40 mL, 0.4 M) to CoCl 2 6H 2 O aqueous solution (40 mL, 0.05 M), and then the hydrophilic carbon cloth (CC) was immersed in the above mixed solution. After standing for 14 hours, it was washed with deionized water and vacuum dried to obtain Co-MOF / CC.

[0030] (2) The Co-MOF / CC obtained in step (1) was cut to a specific size and immersed in a solution containing CoCl 2 6H 2O (0.6 g) in an ethanol solution (100 mL) for 40 min. The sample was taken out, washed with ethanol and dried naturally in air to obtain Co(OH) 2 / CC.

[0031] (3) Co(OH) obtained in step (2) 2 The / CC sample was annealed in air at 450 °C for 1.5 h to obtain D-Co 3 O 4 / CC.

[0032] Performance Test:

[0033] D-Co with oxygen vacancy defects prepared in Example 1 3 O 4 SEM images of the / CC electrocatalysts are shown in Figure 1 As shown, it can be seen that the D-Co with oxygen vacancy defects prepared in Example 1 3 O 4 / CC electrocatalyst is a carbon cloth loaded with nanosheets and obvious pores at the boundary; D-Co with oxygen vacancy defects prepared in Example 1 3 O 4 High-resolution transmission electron microscopy images of the / CC electrocatalysts Figure 2 As shown; Figure 2 In the high-resolution transmission electron microscope image shown, the crystal plane with a lattice spacing of 0.24nm corresponds to Co 3 O 4 (311), and a large number of defects are formed on the nanosheets.

[0034] D-Co with oxygen vacancy defects prepared in Example 1 3 O 4 Electrocatalytic urea wastewater degradation using CC electrocatalysts Figure 3 shown by Figure 3 It can be seen that D-Co 3 O 4 / CC degradation urea concentration-time curve, D-Co 3 O 4 / CC can achieve 97.14% urea removal rate in 45 minutes.

[0035] D-Co with oxygen vacancy defects prepared in Example 1 3 O 4 The stability curve of the CC electrocatalyst during urea degradation is shown in Figure 2. Figure 4 shown by Figure 4 It can be seen that the initial urea removal rate within 90 minutes was 98.0%. After six consecutive cycles of operation for 9 hours, the urea removal rate within 90 minutes remained at 97.5%, which shows that D-Co 3 O4 / CC has good stability.

Claims

1. A D-Co3O4 / CC electrocatalyst material rich in oxygen vacancy defects, characterized in that: The catalyst includes an array of pore-rich nanosheets grown on carbon cloth.

2. The D-Co3O4 / CC electrocatalyst material rich in oxygen vacancy defects according to claim 1, characterized in that: The thickness of the nanosheets in the electrocatalyst is 2-10 nm, and the size of the pores is 1-3 nm.

3. The method for preparing the D-Co3O4 / CC electrocatalyst material rich in oxygen vacancy defects according to claims 1-2, characterized in that: include, S1. Dissolve the cobalt salt in deionized water and immerse the carbon cloth in the solution; Dissolve dimethylimidazole in deionized water, add it to the above solution for reaction, wash, centrifuge and dry to obtain Co-MOF / CC; S2, cutting the Co-MOF / CC and immersing it in an ethanol solution containing cobalt salt for etching, washing the obtained sample with ethanol and drying it naturally in air to obtain Co(OH)2 / CC; S3. Anneal the obtained Co(OH)2 / CC in air and cool it to room temperature in a natural environment to obtain D-Co3O4 / CC.

4. The preparation method according to claim 3, characterized in that: The cobalt salt described in S1 comprises cobalt chloride hexahydrate, and the cobalt salt described in S2 comprises cobalt chloride hexahydrate.

5. The preparation method according to claim 3, characterized in that: The mass ratio of the cobalt chloride hexahydrate to the dimethylimidazole is (0.8-1.5):(2-4).

6. The preparation method according to claim 3, characterized in that: The reaction time described in S1 is 10-14 hours; the etching time described in S2 is 20-40 minutes; and the calcination described in S3 is performed at 250-450° C. for 1.5-2.5 hours.

7. Use of the D-Co3O4 / CC electrocatalyst material rich in oxygen vacancy defects as claimed in claim 1 or 2 in electrocatalytic degradation of urea wastewater.

8. Use of the electrocatalyst material prepared by the preparation method according to any one of claims 3 to 6 in electrocatalytic degradation of urea wastewater.

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