Fe-, N-, and S- Tridoped Carbon Hollow Spheres as Highly Active Electrocatalysts for Oxygen Reduction Reaction

초록

The growing demand for energy and serious environmental problems have promoted the urgent development of sustainable energy conversion and storage devices. Metal-air batteries and fuel cells are regarded as one of the most promising energy storage and conversion device for the next-generation owing to the competitive benefits such as zero-carbon emissions, high energy density, and operating safety. Despite the numerous efforts to utilization of fuel cells, sluggish oxygen reduction reaction (ORR) involving four-electron transfer on the air cathode limit the overall electrochemical kinetics. Until now, although the platinum-based materials have been used as electrocatalysts for ORR owing to outstanding activity, their high cost, scarcity, and low stability have hindered the large-scale commercialization. Thus, enormous research endeavours have been dedicated to exploring efficient and inexpensive electrocatalysts for next-generation energy devices using various transition metal-based materials. Transition metal-nitrogen-doped carbon (M-N-C) have been studied to replace the platinum-based electrocatalysts because of their abundance, various redox property, and durability. Among them, iron-nitrogen-doped carbon (Fe-N-C) electrocatalysts with the locally modified electronic structure and optimal O2 adsorption/desorption energy are considered as attractive alternatives. In this study, we proposed hollow-structured Fe-, N-, and S-tridoped carbon spheres (FeNSC) synthesized by hydrothermal polymerization of polypyrrole on the surface of SiO2 nanosphere, impregnation of Fe ions, chemical etching of a metallic Fe and a SiO2 template, followed by the carbonization with sulphur source. The hollow-structured FeNSC nanospheres showed excellent ORR onset-potential (0.971 V vs. RHE) and half-wave potential (0.877 V vs. RHE), which superior than the state-of-art Pt/C.