具有中空和分级多孔结构的高效Co―N―C氧还原反应催化剂

Highly efficient Co―N―C electrocatalysts with a porous structure for the oxygen reduction reaction

  • 摘要: 开发一种低成本、高效率和稳定的燃料电池的氧还原反应(ORR)催化剂具有极大挑战性。作者通过先在纳米聚苯乙烯(PS)球体表面均匀生长ZIFs,然后分解核壳结构的ZIF@PS,开发了具有中空完整球形结构和大表面积的Co-N-C ORR催化剂,并进行了系统的表征。所制催化剂Co-NHCP-2具有分层的多孔结构,超大的比表面积(1817.24 m2 g−1),吡啶-N、吡咯-N、石墨-N含量高,且Co分布均匀。作为一种高效的电催化剂,Co-NHCP-2催化剂具有高起始电位(0.96 V)、半波电位(0.84 V)和极限电流密度(5.50 mA cm−2)。与市场上的Pt/C催化剂相比,该催化剂在碱性溶液中表现出约4e的ORR途径以及更强的甲醇耐受性和更高的稳定性。这些结果表明,该Co-N-C复合材料可以作为一种有前景的ORR电催化剂。

     

    Abstract: Developing low-cost, highly-efficient and stable catalysts for the oxygen reduction reaction (ORR) of fuel cells is highly desirable yet challenging. We have developed a Co―N―C ORR catalyst with an intact hollow spherical structure and a large surface area which has been systematically characterized. It was produced by the uniform growth of zeolitic imidazolate frameworks (ZIF s) on the surface of nano-polystyrene (PS) spheres followed by their decomposition. Notably, the as-prepared catalyst Co-NHCP-2 (2 represents a mass ratio of 0.6 between Zn(NO3)2·6H2O and 2-methylimidazole) has a porous structure, a super large specific surface area (1817.24 m2 g−1), high contents of pyridinic-N, pyrrolic-N, and graphitic-N, and a uniform Co distribution. As an efficient electrocatalyst, it shows promise in terms of a high onset potential (Eonset) of 0.96 V, a high half-wave potential (E1/2) of 0.84 V, and a limited current density of 5.50 mA cm−2. The catalyst has a nearly 4e pathway for the ORR in an alkaline solution as well as stronger methanol tolerance and higher long-term durability than commercially available Pt/C catalysts. These results show that the obtained material may be a promising electrocatalyst for the ORR.

     

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