Single-atom M–N–C catalysts for oxygen reduction electrocatalysis

Proton-exchange membrane fuel-cells (PEMFCs) are promising energy conversion devices for a renewable energy ecosystem. Developing highly active, durable, and cost-effective cathode catalysts is a significant challenge for the pervasive deployment of PEMFCs. Bio-inspired single-atom M–N–C catalysts have emerged as a promising alternative to overcome the current limitations that originate from the high cost of noble metal catalysts. In this short review, we highlight recent advances in M–N–C catalysts in terms of three notable perspectives: atomic-level understanding and design of mononuclear active sites, the effect of the porous carbon structure on the electrocatalytic performance, and improving catalytic stability. In accordance with these topics, we also suggest future directions to further enhance M–N–C catalysts for highly active and stable PEMFC performance.