Recent advances in active sites identification and new M−N−C catalysts development towards ORR

The M–N–C catalysts are considered potential alternative to Pt-based catalysts for the oxygen reduction reaction (ORR) due to its low cost and promising electrocatalytic performance. However, the catalysts are yet to become truly applicable in terms of activity and stability, and addressing such issues necessitate for indepth understanding in the structure performance relationship, which is remain elusive to date. Herein, we summarize our research progress achieved on M–N–C catalysts in recent years. Firstly, we successfully synthesized atomically dispersed Fe–N–C catalysts and conducted a detailed in-situ spectroscopy study, where the high spin D 2 states of FeN 4 is found to be an active species. Subsequently, in order to address the catalyst utilization and the overall activity of the catalysts, we carried out studies in increasing the active site density through regulating the microstructure of the catalysts. Finally and most importantly, in order to address the intrinsic activity of the catalysts, we carried work in developing new active centers of the M–N–C catalysts, where the new single or dual center catalysts were developed. Some of these centers are able to increase the stability of the catalysts, where the Fenton reaction is largely alleviated, resulting in both enhanced catalytic activity and stability. We hope that as the research continues, commercially available high performance and high stability M–N–C catalysts may eventually be realized.