Fe-N-C类催化剂在碱性燃料电池中的研究进展

Recent Progresses for Fe-N-C Electrocatalysts in Alkaline Fuel Cells

随着阴离子交换膜的出现、发展和应用,碱性燃料电池的优势日趋明显,针对碱性燃料电池的研究也更广泛而深刻.在碱性燃料电池中,除了其固有的对催化剂的高包容性和动力学优越性,阴离子交换膜让阴离子定向迁移,从而实现了很好的水相管理,降低了电池中"水涝"的几率,也提供了更广阔的燃料选择空间.氧还原反应是碱性燃料电池中的重要部分,且其反应动力学相较于氢氧化反应缓慢.因此,选择并研制合适的阴极氧还原反应催化剂,是提高碱性燃料电池性能和促进燃料电池规模化使用的关键.Fe-N-C类催化剂因其在碱性条件下接近甚至优于Pt基催化剂的性能,被视为最有潜力替代Pt的非贵金属催化剂.本文从近5年来Fe-N-C类催化剂的合成方法、催化活性位点和氧还原反应机理以及在燃料电池中的应用三方面进行了综述.

Fuel cells are highly recommended nowadays due to their intrinsic advantages such as high energy conversion efficiency, nearly no pollution, and convenient operation. With the development of anion exchange membrane, alkaline fuel cells have gone through a renaissance thanks to their superiorities such as faster reaction kinetics, wider choices for both fuels and electrocatalysts. It is essential to find an appropriate electrocatalyst for oxygen reduction reaction（ORR） to improve the performance of alkaline fuel cells. Further commercialization of the widely used Pt-based materials has suffered from disadvantages such as scarcity and high cost. As alternatives to largely investigated Pt-based materials, Fe-N-C electrocatalysts have gained increasing attention. However, Fe-N-C electrocatalysts still face problems including imperfect stability and durability, low metal loading, unclear catalytic mechanism and active sites, which has further hindered their design and synthesis. In this review, Fe-N-C electrocatalysts for alkaline fuel cells are discussed from the following three aspects, namely, the synthesis methods, the active sites and mechanisms, and their applications in recent five years. To optimize synthetic conditions, two kinds of typical synthetic methods are overviewed and some synthetic examples in the recent five years are summarized. Three active sites such as FeN_4/C, Fe-N_（2＋2）/C, and Fe-N_2/C, as well as those active sites concerned more widely in recent research for Fe-N-C electrocatalysts are also reviewed, which lays a good foundation for future design of Fe-N-C electrocatalysts. Furthermore, the single cell performance data are provided for the first time in order to enhance the application of the Fe-N-C electrocatalysts in alkaline fuel cells. As a whole, this review aims at providing theoretical support and guidance for future design and synthesis of commercial Fe-N-C electrocatalysts.