Understanding the active site structures and achieving catalytic activity tuning of atomically dispersed FeN4 sites for oxygen reduction reaction.

Abstract

Atomically dispersed Fe-N-C catalysts with high oxygen reduction reaction (ORR) activity have attracted great attention since the last decade. Due to its comparable ORR activity and low material cost, it is a promising platinum-group metal (PGM) free catalyst that can replace the commercialized Pt/C materials; furthermore, it can facilitate the efficiency of the fuel cell technologies and mitigate our dependence on fossil fuels. Great advancements have been made to experimentally optimize the synthesis approach of the Fe-N-C catalysts, enhance the ORR activity, and improve the catalyst stability. Similarly, recent theoretical studies also provide enriched understanding of the active site structures, properties, and reaction mechanisms. In this review, discussions are made upon utilizing combined experimental and computational spectroscopy to reveal the active site structures, employing mechanistic studies to investigate reaction thermodynamics and kinetics, as well as developing scaling relationships to assist the design and development of future PGM free catalyst materials. Furthermore, recent advances in studying Fe-N-C catalysts utilizing electrified surface  and explicit solvation models are  discussed. Not only can these aspects improve the accuracy of theoretical simulation and predictions but also deepen the understanding of the catalyst properties and reaction mechanisms under the effect of surface charges and solvent molecules.