Facile synthesis of hollow structured electrocatalyst with abundant Fe-Nx and C-S-C active sites for oxygen reduction reaction

초록

Recently, metal-air batteries and fuel cells have received worldwide attention as sustainable and efficient energy storage and conversion device for the next generation owing to their attractive benefits such as zero-carbon emission, high energy density, and safety operating condition.[1] Despite of tremendous efforts of researchers, the practical application of air batteries has been hindered by the sluggish kinetics of oxygen reduction reaction (ORR) on the air cathode. To date, although noble metal-based materials have been generally used as state-of-the-art electrocatalyst for ORR owing to outstanding catalytic activity, the high cost, scarcity and low stability significantly hinder the large-scale commercialization of air batteries.[2,3] Therefore, it is necessary to develop efficient and inexpensive electrocatalysts to substitute the precious metal-based electrocatalysts. In this study, we proposed preparation method of hollow-structured N, S doped carbon sphere with abundant Fe-Nx active sites (FeNSC). The hollow-structured FeNSC nanospheres manifested excellent ORR activity and long-term durability. The outstanding ORR performances of FeNSC could be ascribed to the efficient exposure of abundant Fe-Nx active sites induced by well-defined hollow structure. The unique hollow structure of FeNSC also provide reduced ion-diffusion length and large specific surface area, thereby enhancing electrocatalytic ORR performance. Additionally, the electrical conductivity and adsorption of reactant during ORR process can be improved by additional sulfur doping into carbon matrix, which is mainly attributed to high electron spin density of S dopants and introduction of additional active sites for ORR such as thiophen-like C-S-C structure. This research will provide novel insights for designing precious metal-free electrocatalysts with unique hollow structures and heteroatom-doped carbon for energy storage and conversion.