NH3 热处理ZIF-8制备燃料电池氧还原催化剂的研究

Study on the Preparation of Oxygen Reduction Catalyst for Fuel Cell by NH3 Heat Treatment ZIF-8

燃料电池中的催化剂由于制备成本高、工艺复杂等因素严重阻碍了燃料电池的发展, 本文利用NH3热处理ZIF-8制备了一种分级多孔的N掺杂碳材料, 并对其微观结构及电化学行为进行表征分析。结果发现, 化学刻蚀工艺可以在ZIF-8中引入中孔 (2~50nm) 或大孔 (>50nm) , 形成分级多孔结构, 通过控制刻蚀液的pH可以有效调节ZIF-8的孔径。而NH3热处理可以有效调节碳材料中的孔道结构, 增加材料中微孔 (<2nm) 与中孔的数量, 增大材料的比表面积。并且NH3可以作为N源在材料中掺入一定数量的N, 同时可以调节碳材料中的吡啶N与吡咯N向更稳定的石墨N转化, 通过控制NH3热处理的温度可以对碳材料的孔隙结构及N掺入含量进行合理控制。本文制备的N-C@2. 5pH-1000电催化性能优异, 具有和商用Pt/C催化剂相近的氧化还原反应 (oxygen reduction reaction, ORR) 活性和更加优良的循环稳定性。本文提出的合成策略为制备高效廉价的燃料电池催化剂提供了新的思路。

The development of catalyst in fuel cell is seriously hampered due to high preparation costs and complex processes. In this paper, a graded porous N-doped carbon material was prepared using NH3 heat treatment ZIF-8, and its microstructure and electrochemical behavior. were characterized and analyzed. It is found that the chemical etching process can introduce mesoporous (2-50nm) or macropores (>50nm) into ZIF-8 to form. a graded porous structure, and the pore size of ZIF-8 can be effectively adjusted by controlling the pH of the etching solution. The NH3 heat treatment can effectively adjust the pore structure in carbon materials, increase the number of micropores (<2nm) and mesopores in the materials, and increase the specific surface area of the materials. NH3 can be used as an N source to dope the material with a certain amount of N. It can also regulate the conversion of pyridine N and pyrrole N in the carbon material to the more stable graphite N, and the pore structure and N doping content of the carbon material can be reasonably controlled by controlling the temperature of NH3 heat treatment. The N-C@2. 5pH-1000 prepared in this paper has excellent electrocatalytic performance, similar oxygen reduction reaction (ORR) activity and better cycling stability than commercial Pt/C catalysts. The synthetic strategy proposed in this paper provides a new idea for the preparation of efficient and inexpensive fuel cell catalysts.