CN111883785B - Co-N Co-doped drum-shaped porous carbon catalyst and preparation method and application thereof - Google Patents

Abstract

The invention discloses a Co-N Co-doped drum-shaped porous carbon catalyst and a preparation method and application thereof. According to the method, a drum-shaped zeolite imidazole framework structure synthesized by a double coordination strategy is used as a precursor, and the Co-N Co-doped drum-shaped porous carbon catalyst can be prepared through a simple pyrolysis step. The method has the advantages of simple process, abundant raw material sources and low cost, and the prepared catalyst shows better electrochemical activity, stability and methanol resistance than commercial Pt/C, and has good prospects in cathode oxygen reduction reactions of metal-air batteries and fuel cells.

Description

Co-N Co-doped drum-shaped porous carbon catalyst and preparation method and application thereof

Technical Field

The invention relates to the fields of electro-catalysis, metal-air batteries and fuel cells, in particular to a Co-N Co-doped drum-shaped porous carbon catalyst and a preparation method and application thereof.

Background

The oxygen reduction reaction ORR is a key reaction in the energy conversion process of metal air batteries and fuel cells. Currently, there are two recognized pathways for ORR reactions: one is a two-step two-electron process (2 e) to generate peroxide^–) (ii) a The other is an ideal one-step four-electron process (4 e) for water production desired for metal-air cells and fuel cells^–). Although Pt-based catalysts exhibit ideal 4e for ORR^–However, the large-scale application of the noble metal Pt is limited by the defects of scarcity, high cost, easy poisoning and the like of the noble metal Pt. Therefore, the development of low-cost and high-performance (high stability and high activity) non-noble metal catalysts has been a research focus in the fields of metal air batteries and fuel cells.

A great deal of research work is focused on the ORR electrocatalyst constructed based on the active sites of the transition metals, and it is found that the transition metal and nitrogen Co-doped carbon catalyst (M-N-C, M stands for Fe, Co, Zn, Ni, etc.) exhibits good ORR activity and durability. Metal Organic Frameworks (MOFs) are a new type of porous material made of metal combined with organic ligands, with high specific surface area and adjustable nanoporous structures, atomsDispersed metal sites, excellent designability, etc., and is considered as an ideal precursor for preparing an M-N-C type ORR electrocatalyst. After MOFs are thermally cracked, the product not only keeps the original porous and hollow structure, but also has M-N₄The connection is converted into a stable, dense and uniformly distributed M-N-C structure, thereby showing higher ORR electrocatalytic performance. In recent years, many studies have been reported on the synthesis of ORR catalysts from Co-based MOFs as precursors, for example: (1) ACS Catalysis in 2018 reports that Co-based imidazole (Co-ZIFs) is used as a precursor, a nitrogen-doped porous carbon fixed Co monatomic catalyst is constructed by combining pyrolysis and etching, and the catalyst has excellent bifunctional electrocatalytic activity and mechanical flexibility in oxygen reduction and oxygen precipitation reactions; (2) advanced Functional Materials reports that a leaf-shaped cobalt-zinc bimetallic imidazole skeleton precursor is synthesized in one step in 2018, and a cobalt and nitrogen co-doped carbon nanotube catalyst is obtained through high-temperature pyrolysis and shows excellent electrochemical activity and stability in oxygen reduction and oxygen precipitation; (3) 2018 Applied Surface Science reports that polyacrylonitrile-coated cobalt-based imidazole fiber is used as a precursor to synthesize legume-shaped Co/CoO_x-N-C catalyst, showing good electrocatalytic effect on ORR; (4) 2019 Chemical Engineering Journal reports that a polystyrene microsphere @ cobalt-based imidazole core-shell structure is synthesized by polystyrene microspheres, cobalt nitrate and dimethyl imidazole, and then a layered Co and N Co-doped carbon nanotube hollow microsphere is prepared by pyrolysis, so that the ORR (organic radio response) performance of the material is effectively improved, and the zinc air battery has 183.8 mW cm^–2The power density of (d); (5) journal of the American Chemical Society in 2019 reported the synthesis of a cobalt-iron bimetallic catalyst with high ORR performance based on a cobalt-zinc bimetallic imidazole rhombohedral skeleton. However, the research on designing and synthesizing a drum-shaped zeolite imidazole framework precursor by using benzimidazole and 2-methylimidazole as ligands through a double coordination strategy, preparing a Co-N codoped drum-shaped porous carbon catalyst by pyrolysis and applying the Co-N codoped drum-shaped porous carbon catalyst to an electro-catalytic oxygen reduction cell and a zinc-air battery is not reported in documents and patents.

Disclosure of Invention

The invention aims to provide a Co-N Co-doped drum-shaped porous carbon catalyst and a preparation method and application thereof aiming at the defects of the prior art. The method has the advantages of simple process, abundant raw material sources and low cost, and the prepared catalyst shows better electrochemical activity, stability and methanol resistance than commercial Pt/C, and has good prospects in cathode oxygen reduction reactions of metal-air batteries and fuel cells.

The technical scheme for realizing the purpose of the invention is as follows:

the preparation method of the Co-N Co-doped drum-shaped porous carbon catalyst is different from the prior art in that the preparation method comprises the following steps:

1) adding 7 mmol of benzimidazole and 40-150 mg of PVP into a container filled with 30 mL of methanol, adding 10 mL of a methanol solution of cobalt nitrate after uniform ultrasonic dispersion, wherein the methanol solution of cobalt nitrate contains 1 mmol of cobalt nitrate, adding 35 mL of a methanol solution of 2-methylimidazole after ultrasonic treatment for 10 minutes, adding 1-8 mmol of 2-methylimidazole in the methanol solution of 2-methylimidazole, continuing ultrasonic treatment for 10 minutes, then magnetically stirring for 24 hours, centrifuging, washing and drying to obtain a blue drum-shaped zeolite imidazole framework precursor, namely D-ZIFs;

2) placing the obtained drum-shaped zeolite imidazole framework D-ZIFs sample in a quartz tube furnace, and performing reaction in a reaction system under the conditions of N₂The Co-N codoped drum-shaped porous carbon catalyst, namely Co-N-PC, can be prepared by pyrolysis for 3 h at the temperature of 600-1000 ℃ under protection_D。

Co-N Co-doped drum-shaped porous carbon catalyst, namely Co-N-PC prepared by using preparation method_D。

The Co-N codoped drum-shaped porous carbon catalyst prepared by the preparation method is applied to the oxygen reduction reaction of the cathode of a metal air battery and a fuel battery.

The technical scheme is that benzimidazole and 2-methylimidazole are used as ligands to synthesize a drum-shaped zeolite imidazole framework structure precursor through a double coordination strategy, and then the drum-shaped porous carbon catalyst Co-doped with Co-N is prepared through pyrolysis.

According to the technical scheme, a drum-shaped zeolite imidazole framework structure synthesized by a double coordination strategy is used as a precursor, and the Co-N Co-doped drum-shaped porous carbon catalyst can be prepared through a simple pyrolysis step.

The method has the advantages of simple process, abundant raw material sources and low cost, and the prepared catalyst shows better electrochemical activity, stability and methanol resistance than commercial Pt/C, and has good prospects in cathode oxygen reduction reactions of metal-air batteries and fuel cells.

Drawings

FIG. 1 is a schematic flow chart of the preparation of a Co-N Co-doped drum-shaped porous carbon catalyst in the example;

FIG. 2 is an SEM image of a Co-N Co-doped drum-shaped porous carbon catalyst prepared in the example;

FIG. 3 is a TEM image of the Co-N Co-doped drum-shaped porous carbon catalyst prepared in example;

FIG. 4 shows Co-N-C prepared in example_M，Co-N-C_BM，Co-N-C_B，Co-N-PC_DAnd commercial Pt/C catalyst in O₂A schematic of linear sweep voltammograms in saturated 0.1M potassium hydroxide solution;

FIG. 5 shows Co-N-PC prepared in example_DAnd commercial Pt/C catalyst in O₂Saturated 0.1M potassium hydroxide solution at 0.3V_RHESchematic diagram of the chronoamperometric curve of the methanol resistance test;

FIG. 6 shows Co-N-PC prepared in example_DAnd commercial Pt/C catalyst in O₂Saturated 0.1M potassium hydroxide solution at 0.3V_RHEThe lower chronoamperometric curve is shown.

Detailed Description

The invention will be further elucidated with reference to the drawings and examples, without however being limited thereto.

Example (b):

referring to FIG. 1, 1) adding 7 mmol of benzimidazole and 40 mg-150 mg of PVP into a container filled with 30 mL of methanol, adding 10 mL of methanol solution of cobalt nitrate after uniform ultrasonic dispersion, wherein the methanol solution of cobalt nitrate contains 1 mmol of cobalt nitrate, adding 35 mL of methanol solution of 2-methylimidazole after ultrasonic treatment for 10 minutes, wherein the methanol solution of 2-methylimidazole contains 1 mmol-8 mmol of 2-methylimidazole, continuing ultrasonic treatment for 10 minutes, then magnetically stirring for 24 hours, centrifuging, washing and drying to obtain a blue drum-shaped zeolite imidazole framework precursor, namely D-ZIFs;

2) placing the obtained drum-shaped zeolite imidazole framework D-ZIFs sample in a quartz tube furnace, and performing reaction in a reaction system under the conditions of N₂The Co-N codoped drum-shaped porous carbon catalyst, namely Co-N-PC, can be prepared by pyrolysis for 3 h at the temperature of 600-1000 ℃ under protection_D。

Co-N Co-doped drum-shaped porous carbon catalyst, namely Co-N-PC prepared by using preparation method_D。

The Co-N codoped drum-shaped porous carbon catalyst prepared by the preparation method is applied to the oxygen reduction reaction of the cathode of a metal air battery and a fuel battery.

For electrochemical performance comparison, Co-N-C was prepared using 2-methylimidazole, benzimidazole and benzimidazole ligands, respectively_M，Co-N-C_BMAnd Co-N-C_BA catalyst.

SEM, TEM, STEM and BET test results show that the Co-N Co-doped drum-shaped porous carbon catalyst prepared by the double coordination method has a rough porous structure on the surface and has a higher Co-N-C ratio than that of the Co-N-C_M，Co-N-C_BMAnd Co-N-C_BLarger specific surface area and porosity, and good dispersibility and uniformity of each component in the catalyst prepared according to the bidentate method of the present example, as shown in fig. 2 and 3.

The Co-N-C prepared simultaneously in the example was compared by linear sweep voltammetry_M，Co-N-C_BM，Co-N-C_B，Co-N-PC_DAnd electrocatalytic performance of commercial Pt/C on oxygen reduction reaction in 0.1M potassium hydroxide solution, the results show that Co-N-PC_DHalf-wave potential (0.886V) and limiting current density (5.65 mA cm) for oxygen reduction reaction^-2) Are all obviously superior to the three comparative samples and the commercial Pt/C catalyst (0.876V, 5.2 mA cm)^-2) Showing that Co-N-PC prepared according to the bidentate method of this example_DThe catalysts showed the best electrocatalytic activity for oxygen reduction in alkaline medium, figure 4 shows the different catalysts in O₂Linear sweep voltammograms in saturated 0.1M potassium hydroxide solution.

Methanol resistance and stability were compared by chronoamperometry, and Co-N-PC is shown in FIGS. 5 and 6, respectively_DAnd commercial Pt/C catalyst in O₂Saturated 0.1M potassium hydroxide solution at 0.3V_RHEThe chronoamperometric curves for the methanol resistance test and the 28800 s stability test were performed and the results show that the current density of commercial Pt/C decreases sharply after the 2M methanol solution was added rapidly at 290 s, while Co-N-PC_DThe current density of the prepared Co-N-PC is not obviously changed, which indicates that the prepared Co-N-PC_DThe catalyst has excellent methanol resistance, and in addition, after 28800 s chronoamperometry, Co-N-PC_DThe current density retention of the catalyst (96.0%) was significantly higher than that of the commercial Pt/C (87.4%), confirming that the Co-N-PC prepared_DThe catalyst has excellent electrochemical stability.

Claims (3)

1. The preparation method of the Co-N Co-doped drum-shaped porous carbon catalyst is characterized by comprising the following steps of:

1) adding 7 mmol of benzimidazole and 40-150 mg of PVP into a container filled with 30 mL of methanol, adding 10 mL of a methanol solution of cobalt nitrate after uniform ultrasonic dispersion, wherein the methanol solution of cobalt nitrate contains 1 mmol of cobalt nitrate, adding 35 mL of a methanol solution of 2-methylimidazole after ultrasonic treatment for 10 minutes, adding 1-8 mmol of 2-methylimidazole in the methanol solution of 2-methylimidazole, continuing ultrasonic treatment for 10 minutes, then magnetically stirring for 24 hours, centrifuging, washing and drying to obtain a blue drum-shaped zeolite imidazole framework precursor, namely D-ZIFs;

2) placing the obtained drum-shaped zeolite imidazole framework D-ZIFs sample in a quartz tube furnace, and performing reaction in a reaction system under the conditions of N₂The Co-N codoped drum-shaped porous carbon catalyst, namely Co-N-PC, can be prepared by pyrolysis for 3 h at the temperature of 600-1000 ℃ under protection_D。

2. Co-N Co-doped drum-shaped porous carbon catalyst (Co-N-PC) prepared by the preparation method of claim 1_D。

3. The use of the Co-doped drum porous carbon catalyst of claim 2 in cathode oxygen reduction reactions in metal air batteries and fuel cells.

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