Co / Mxene composite catalyst for oxygen reduction catalysis as well as preparation method and application of Co / Mxene composite catalyst

Abstract

The invention discloses a Co / Mxene composite catalyst for oxygen reduction catalysis as well as a preparation method and application of the Co / Mxene composite catalyst. Belongs to the technical field of metal-air cell and fuel cell catalysts, clusters containing cobalt salt and ligands are easily adsorbed by Mxene nanosheets by utilizing amphipathicity and complexing action on cobalt ions of organic small molecule ligands, and under the inhibition of Mxene surface functional groups, the cobalt ions in the Mxene nanosheets are adsorbed by the Mxene nanosheets, so that the cobalt ions in the Mxene nanosheets are adsorbed by the Mxene nanosheets. The small particles cannot be further agglomerated in the calcining process of the inert atmosphere, so that the cobalt nanoparticles can be synthesized on the high-conductivity Mxene nanosheet substrate. The catalyst has efficient and stable oxygen reduction performance on the premise of maintaining high conductivity of Mxene; the cobalt content is low, and low-cost preparation can be achieved; the specific surface area is relatively large, and cobalt nanoparticles are uniformly distributed on the surface of Mxene; the catalyst has excellent conductivity, can be applied to membrane electrodes of zinc-air cells, aluminum-air cells and fuel cells, and provides an efficient and stable catalyst.

Description

Technical Field

[0001] The present invention belongs to the technical field of metal-air batteries and fuel cell catalysts, and in particular relates to a Co / Mxene composite catalyst for oxygen reduction catalysis, a preparation method and an application thereof. Background Art

[0002] Since the Industrial Revolution, fossil energy such as oil and coal have caused serious environmental pollution, and their limited and non-renewable characteristics have restricted economic development. Therefore, it is crucial to study sustainable energy and its conversion, which can simultaneously promote economic development and environmental improvement and improve energy efficiency. Compared with traditional fuel engines, fuel cell systems such as hydrogen and oxygen, metal and solid oxide fuel cells have significant advantages in energy efficiency, environmental protection and sustainability. However, the key components of membrane electrodes and oxygen reduction catalysts such as precious metals such as Pt, Ru, and Ir are expensive and scarce, which restricts the scale of commercial applications.

[0003] Therefore, it is crucial to use Group VIII transition metals such as Fe, Co, and Ni to replace precious metals to develop highly active, long-life, and inexpensive oxygen reduction catalysts. Currently, mature metal particles, graphene, and carbon nanotube composite catalysts show excellent electrochemical catalytic activity. For cobalt-based catalysts, the more defects on their surfaces can bring about a larger reaction active area, but this often leads to greater obstacles to the transmission of electrons on their surfaces and interfaces. In order to increase the conductivity of the catalyst, it is a better choice to composite it with a highly conductive carbon-based substrate, but in order to make the carbon-based substrate have a higher degree of graphitization and corresponding conductivity, it is necessary to calcine at a higher temperature, which will lead to excessive agglomeration of cobalt-based active substances and greatly reduce the reaction active area.

[0004] MXenes have excellent electrical conductivity. For example, ultrathin, compact MXene films with highly aligned flakes have very high electrical conductivity of up to 15100 S / cm. Experimentally, metal MXenes, especially Ti 3 C 2 T x The film has higher conductivity than any other 2D material, including exfoliated graphene, metal sulfides / hydroxides, etc.

[0005] Therefore, in order to achieve both high conductivity and high reactivity, it is of great significance to reduce the agglomeration of Co-based active materials by selecting MXene as the conductive substrate and avoiding the use of higher calcination temperatures. Summary of the invention

[0006] In view of this, the technical problem to be solved by the present invention is to provide a Co / Mxene composite catalyst for oxygen reduction catalysis and a preparation method and application thereof. The Co / Mxene composite catalyst provided by the present invention has good catalytic performance and stability in oxygen reduction reaction, and can be applied to zinc-air batteries, aluminum-air batteries and fuel cells.

[0007] The technical solution of the present invention is as follows: A Co / Mxene composite catalyst for oxygen reduction catalysis is prepared by the following steps: a) mixing the cobalt salt and the ligand with ethanol and continuously stirring to obtain a mixed solution ①; b) adding the MXene dispersion into the mixed solution ①, stirring and aging the mixture to obtain a mixed solution ②; c) filtering and drying the mixed solution ②, and grinding it into fine powder to obtain a solid mixture ①; d) calcining the solid mixture ① to obtain a catalyst.

[0008] A method for preparing a Co / Mxene composite catalyst for oxygen reduction catalysis comprises the following steps: a) mixing the cobalt salt and the ligand with ethanol and continuously stirring to obtain a mixed solution ①; b) adding the MXene dispersion into the mixed solution ①, stirring and aging the mixture to obtain a mixed solution ②; c) filtering and drying the mixed solution ②, and grinding it into fine powder to obtain a solid mixture ①; d) calcining the solid mixture ① to obtain a catalyst.

[0009] Preferably, in step a), the cobalt salt is selected from one or more of cobalt nitrate, cobalt chloride and its hydrate, cobalt acetylacetonate and cobaltocene; the ligand is selected from one or more of dicyandiamide, tetrabutylammonium iodide and o-phenanthroline; Preferably, in step b), the Mxene is selected from Ti 3 C 2 、Ti 2 C. Ti 2 N, Nb 2 C、Nb 4 C 3 、 2 C. Ta 4 C 3 、V 2 C.V 3 C 2 Cr 2 C.Cr 3 C 2 、(Ti 0.5 Nb0.5 ) 2 C. Ti 3 (C 0.5 N 0.5 ) 2 、Mo 2 C or Mo 3 C 2 One or more of; the Mxene dispersion is an ethanol solution with a concentration of 1%-20%wt; Preferably, in steps a) and b), the stirring method is selected from one of mechanical stirring, magnetic stirring or ultrasonic stirring; Preferably, in step a), the stirring temperature is 15 to 35° C., and the stirring time is 0.5 to 2 h; in step b), the stirring aging temperature is 15 to 35° C., and the stirring time is 12 to 36 h; Preferably, in step c), the filtering method is vacuum filtration, and the drying method is selected from one of forced air drying, vacuum drying or freeze drying; Preferably, in step d), the calcination treatment is carried out in a high-purity nitrogen atmosphere, a high-purity argon atmosphere or under vacuum conditions; the calcination treatment temperature is 300 to 700° C., the calcination treatment time is 0.5 h to 6 h, and the calcination treatment heating rate is 10 to 20° C. / min; Preferably, the molar ratio of the ligand to the cobalt salt is (1-8):1; the mass ratio of the Mxene to the metal salt is (1-50):1; the mass ratio of the cobalt salt to ethanol is 1:(5-500); Preferably, in the Co / Mxene composite catalyst for oxygen reduction catalysis, the cobalt metal is bonded to the Mxene nanosheet carrier.

[0010] Preferably, the membrane electrode of the Co / Mxene composite catalyst can be applied to zinc-air batteries, aluminum-air batteries and fuel cells.

[0011] Beneficial effects: Compared with the prior art, the present invention utilizes the amphiphilicity and complexing effect of organic small molecule ligands on cobalt ions to make clusters containing cobalt salts and ligands easily adsorbed by Mxene nanosheets. On the one hand, the functional groups of Mxene itself have an anchoring effect on cobalt particles, which inhibits the agglomeration of cobalt particles; on the other hand, the calcination temperature is lower than that of conventional carbon-based materials, which further prevents serious agglomeration of cobalt metal particles; thereby, small particles of cobalt can be uniformly distributed on Mxene nanosheets. In addition, compared with traditional carbon-based materials, such as porous carbon, graphene, etc., Mxene has better electrical conductivity. The Co / Mxene catalyst prepared by the present invention has a higher reaction concentration and a higher catalytic activity for oxygen reduction when used in fuel cells. The process route of the present invention is simple, does not require complex synthesis equipment, is low in cost, and is suitable for large-scale industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 The Co / Ti synthesized in Example 1 3 C 2 Transmission electron microscopy of catalyst.

[0013] Figure 2 The stability of commercial Pt / C oxygen reduction catalysis is shown in the comparative example.

[0014] Figure 3 The Co / Ti synthesized in Example 1 3 C 2 Catalytic stability of oxygen reduction catalysts. DETAILED DESCRIPTION

[0015] All raw materials of the present invention have no particular limitation on their sources, and can be purchased from the market or prepared according to conventional methods known to those skilled in the art.

[0016] In order to further understand the present invention, the Co / Mxene composite catalyst for oxygen reduction catalysis and the preparation method thereof provided by the present invention are described below in conjunction with examples, and the protection scope of the present invention is not limited by the following examples.

[0017] Example 1 The drug is analytically pure and there is no purification step. 2 6H 2 O (1.0 g) and o-phenanthroline (2.5 g) were mixed with 0.3 L ethanol and magnetically stirred at 25 °C for 0.5 h to obtain a mixed solution ①; then, Ti 3 C 2 T xEthanol solution (5%wt, 80g) was added to the mixed solution ① and magnetically stirred at 25℃ for 12h to obtain a mixed solution ②. Subsequently, the mixed solution ② was dried by a freeze dryer, ground into fine particles, and the collected product was obtained to obtain a solid mixture ①. Finally, the solid mixture ① was heated to 600℃ in an argon atmosphere at a heating rate of 10℃ / min and calcined for 2h to obtain Co / Ti 3 C 2 catalyst.

[0018] Example 2 The drug is analytically pure and there is no purification step. 2 6H 2 O (5.0 g) and o-phenanthroline (11.2 g) were mixed with 1.5 L of ethanol and mechanically stirred at 35 °C for 2 h to obtain a mixed solution ①; then, Nb 4 C 3 Ethanol solution (5%wt, 500g) was added to the mixed solution ① and mechanically stirred at 25℃ for 12h to obtain a mixed solution ②. Subsequently, the mixed solution ② was vacuum filtered and dried in a vacuum drying oven, ground into fine particles and collected to obtain a solid mixture ①. Finally, the solid mixture ① was heated to 700℃ in an argon atmosphere at a heating rate of 10℃ / min and calcined for 4h to obtain Co / Nb 4 C 3 catalyst.

[0019] Example 3 The drug is analytically pure and there is no purification step. 2 6H 2 O (0.4 g) and o-phenanthroline (1.0 g) were mixed with 0.1 L ethanol and magnetically stirred at 15 °C for 0.5 h to obtain a mixed solution ①; then, Ti 3 C 2 T x Ethanol solution (2%wt, 100g) was added to the mixed solution ① and magnetically stirred at 15℃ for 24h to obtain a mixed solution ②; then, the mixed solution ② was dried by a freeze dryer, ground into fine particles and collected to obtain a solid mixture ①; finally, the solid mixture ① was heated to 600℃ in an argon atmosphere at a heating rate of 20℃ / min and calcined for 0.5h to obtain Co / Ti 3 C 2 catalyst.

[0020] Example 4 The drug was analytically pure and no purification step was required. Cobalt bis(cyclopentadienyl) (1.0 g) and tetrabutylammonium iodide (3.0 g) were mixed with 0.25 L of ethanol and magnetically stirred at 25 °C for 0.5 h to obtain a mixed solution ①; then, Ti 2C ethanol solution (5%wt, 80g) was added to the mixed solution ①, and magnetic stirring was performed at 25℃ for 18h to obtain a mixed solution ②; then, the mixed solution ② was dried by a freeze dryer, ground into fine particles, and the collected product was obtained to obtain a solid mixture ①; finally, the solid mixture ① was heated to 700℃ in a nitrogen atmosphere at a heating rate of 10℃ / min and calcined for 2h to obtain Co / Ti 2 C catalyst.

[0021] Example 5 The drug was analytically pure and no purification step was required. Cobalt acetylacetonate (0.5 g) and dicyandiamide (1.2 g) were mixed with 0.2 L ethanol and magnetically stirred at 25 °C for 1 h to obtain a mixed solution ①; then, Ti 3 (C 0.5 N 0.5 ) 2 Ethanol solution (1%wt, 150g) was added to the mixed solution ① and magnetically stirred at 25℃ for 24h to obtain a mixed solution ②; then, the mixed solution ② was vacuum filtered and dried in a blower dryer, ground into fine pieces and collected to obtain a solid mixture ①; finally, the solid mixture ① was heated to 650℃ in a vacuum furnace at a heating rate of 10℃ / min and calcined for 2h to obtain Co / Ti 3 (C 0.5 N 0.5 ) 2 catalyst.

[0022] Comparative Example Commercial Pt / C catalyst: The commercial Pt / C catalyst was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., with a Pt content of 5%.

[0023] Experimental results and analysis The Co / Ti synthesized in Example 1 3 C 2 The catalyst was characterized by transmission electron microscopy, electrochemical testing, etc. Figure 1 , 2 , 3 shows the results. Figure 1 The transmission electron microscopy diagram shows that the cobalt nanoparticles are evenly distributed on the Ti flakes. 3 C 2 On the surface, the cobalt particles are very small, about 5nm. Figure 2 The electrochemical cyclic voltammogram of commercial Pt / C in the comparative example is shown. It can be seen from the figure that in the cyclic voltammogram test of commercial Pt / C, after only 500 cycles, the half-wave potential decays far more than 10mV; Figure 3 The Co / Ti synthesized in Example 1 is shown 3 C 2The electrochemical cyclic voltammogram of the catalyst shows that after 10,000 cycles of cyclic voltammogram testing, the half-wave potential decay is almost non-existent, and after 30,000 cycles, the half-wave potential decay is only 13 mV. 3 C 2 The catalyst material showed excellent electrochemical stability.

[0024] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A Co / Mxene composite catalyst for oxygen reduction catalysis, characterized in that: Prepared by the following steps: a) mixing the cobalt salt and the ligand with ethanol and continuously stirring to obtain a mixed solution ①; b) adding the MXene dispersion into the mixed solution ①, stirring and aging the mixture to obtain a mixed solution ②; c) filtering and drying the mixed solution ②, and grinding it into fine powder to obtain a solid mixture ①; d) calcining the solid mixture ① to obtain a catalyst.

2. A method for preparing a Co / Mxene composite catalyst for oxygen reduction catalysis, characterized in that: a) mixing the cobalt salt and the ligand with ethanol and continuously stirring to obtain a mixed solution ①; b) adding the MXene dispersion into the mixed solution ①, stirring and aging the mixture to obtain a mixed solution ②; c) filtering and drying the mixed solution ②, and grinding it into fine powder to obtain a solid mixture ①; d) calcining the solid mixture ① to obtain a catalyst.

3. The method for preparing a Co / Mxene composite catalyst for oxygen reduction catalysis according to claim 2, characterized in that: In step a), the cobalt salt is selected from one or more of cobalt nitrate, cobalt chloride and its hydrate, cobalt acetylacetonate and cobaltocene; and the ligand is selected from one or more of dicyandiamide, tetrabutylammonium iodide and o-phenanthroline.

4. The method for preparing a Co / Mxene composite catalyst for oxygen reduction catalysis according to claim 2, characterized in that: In step b), the Mxene is selected from Ti3C2, Ti2C, Ti2N, Nb2C, Nb4C3, Ta2C, Ta4C3, V2C, V3C2, Cr2C, Cr3C2, (Ti 0.5 Nb 0.5 )2C、Ti3(C 0.5 N 0.5 )2, one or more of Mo2C or Mo3C2; the Mxene dispersion is an ethanol solution with a concentration of 1%-20%wt.

5. The method for preparing a Co / Mxene composite catalyst for oxygen reduction catalysis according to claim 2, characterized in that: In steps a) and b), the stirring method is selected from mechanical stirring, magnetic stirring or ultrasonic stirring.

6. The method for preparing a Co / Mxene composite catalyst for oxygen reduction catalysis according to claim 2, characterized in that: In step a), the stirring temperature is 15-35° C., and the stirring time is 0.5-2 h; in step b), the stirring aging temperature is 15-35° C., and the stirring time is 12-36 h.

7. The method for preparing a Co / Mxene composite catalyst for oxygen reduction catalysis according to claim 2, characterized in that: In step c), the filtering method is vacuum filtration, and the drying method is selected from one of forced air drying, vacuum drying or freeze drying.

8. The method for preparing a Co / Mxene composite catalyst for oxygen reduction catalysis according to claim 2, characterized in that: In step d), the calcination treatment is carried out in a high-purity nitrogen atmosphere, a high-purity argon atmosphere or under vacuum conditions; the calcination treatment temperature is 300-700° C., the calcination treatment time is 0.5 h-6 h, and the calcination treatment heating rate is 10-20° C. / min.

9. The method for preparing a Co / Mxene composite catalyst for oxygen reduction catalysis according to claim 2, characterized in that: The molar ratio of the ligand to the cobalt salt is (1-8):1; the mass ratio of the Mxene to the metal salt is (1-50):1; and the mass ratio of the cobalt salt to ethanol is 1:(5-500).

10. Use of a Co / Mxene composite catalyst for oxygen reduction catalysis according to any one of claims 1 to 9, characterized in that: The cobalt metal is bonded to the Mxene nanosheet carrier; the catalyst is applied to zinc-air batteries, aluminum-air batteries or fuel cells.

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