Acta Chim. Sinica ›› 2019, Vol. 77 ›› Issue (1): 60-65.DOI: 10.6023/A18080323 Previous Articles     Next Articles

Article

活性位高度暴露的钴/氮/碳电催化剂的构建及氧还原性能研究

张志琦, 葛承宣, 陈玉刚, 吴强, 杨立军, 王喜章, 胡征   

  1. 介观化学教育部重点实验室 南京大学化学化工学院 南京 210023
  • 收稿日期:2018-08-07 出版日期:2019-01-15 发布日期:2018-11-08
  • 通讯作者: 吴强 E-mail:wqchem@nju.edu.cn
  • 基金资助:

    项目受国家重点研发计划(No.2017YFA0206500)、国家自然科学基金(Nos.21773111,21473089,51571110,21573107)、常州市科技计划(No.CE20130032)、江苏高校优势学科建设工程资助项目和中央高校基本科研业务费专项资金资助.

Construction of Cobalt/Nitrogen/Carbon Electrocatalysts with Highly Exposed Active Sites for Oxygen Reduction Reaction

Zhang Zhiqi, Ge Chengxuan, Chen Yugang, Wu Qiang, Yang Lijun, Wang Xizhang, Hu Zheng   

  1. Key Laboratory of Mesoscopic Chemistry of MOE, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210023, China
  • Received:2018-08-07 Online:2019-01-15 Published:2018-11-08
  • Contact: 10.6023/A18080323 E-mail:wqchem@nju.edu.cn
  • Supported by:

    Project supported by the National Key Research and Development Program of China (No. 2017YFA0206500), National Natural Science Foundation of China (Nos. 21773111, 21473089, 51571110, 21573107), Changzhou Technology Support Program (No. CE20130032), Priority Academic Program Development of Jiangsu Higher Education Institution, and Fundamental Research Funds for the Central Universities.

The ever-growing crises of fossil fuel shortage and environmental pollution urgently call for the exploration of clean and renewable energies. Fuel cells present high power efficiency and emit zero pollutants, showing great potential in the future energy system. The main bottleneck of fuel cell commercialization is the sluggish oxygen reduction reaction (ORR) at the cathode. To date, the most active electrocatalysts for ORR are platinum and its alloys. However, the scarcity, high cost and susceptibility to methanol crossover of precious metals hinder the large-scale application of fuel cells. The development of highly efficient and stable non-precious metal ORR electrocatalysts with high resistance to methanol crossover is of great significance. M/N/C (M=Fe, Co, etc.) catalysts are attractive non-precious metal based ORR electrocatalysts and their performance depends on the density of active sites on the catalyst surface. The common synthesis of M/N/C catalysts is to pyrolyze the mixture of metal salt, nitrogen-containing precursor and carbon support. However, so-synthesized catalysts usually contain large metal-based particles, leading to the shortcomings of low density and partial embedding of active sites. Graphitic carbon nitride (g-C3N4) with high concentration of pyridine-like nitrogen in heptazine heterorings can provide abundant and uniform nitrogen coordination sites, which can capture metal ions by the interaction between metal ions and N sites. In addition, g-C3N4 would be decomposed largely during pyrolysis, which is beneficial to form highly exposed M/N/C active sites by pyrolyzing the g-C3N4 with adsorbed metal ions. Herein, we reported the construction of Co/N/C electrocatalysts with highly exposed active sites. Specifically, the g-C3N4 was uniformly supported on the surface of high-conductive hierarchical carbon nanocages (hCNC) by the impregnation and pyrolysis process, leading to the formation of g-C3N4/hCNC composite. Co2+ ions were then captured by the g-C3N4 species on the surface owing to the interaction between the lone pair electrons of nitrogen and the Co2+ ions, and the subsequent pyrolysis led to the Co/N/C catalysts with highly exposed active sites, high conductivity and multiscale pore structure. The optimized catalyst obtained at 800℃ exhibits excellent ORR performance in alkaline medium, with a high onset potential (0.97 V) comparable to commercial Pt/C catalyst, while much better stability and high immunity to methanol crossover. This study demonstrates an effective strategy for the construction of high-efficient M/N/C catalysts with highly exposed active sites.

Key words: cobalt/nitrogen/carbon, oxygen reduction electrocatalysts, highly exposed active sites, carbon nanocages, fuel cell