Recent advances in tuning the electronic structures of atomically dispersed M-N-C materials for efficient gas-involving electrocatalysis

Owing to the intriguing physical, chemical, and electronic properties, atomically dispersed M-N-C materials are emerging as the most promising alternatives to noble metals for many gas-involving electrochemical reactions, like the oxygen evolution reaction, hydrogen evolution reaction, oxygen reduction reaction, and carbon dioxide reduction reaction. Current research on achieving high performance M-N-Cs is based on two aspects: one is to increase the density of active sites through a selection of appropriate precursors and smart design of the synthetic method, and the other is to boost the intrinsic activity of active sites through electronic structure modulation. In this review, we focus on the latter one and comprehensively summarize the reported strategies, including a judicious choice of central metal ions, modification of the carbon basal plane, and adjustment of the coordination environment of central metal ions, for achieving the optimized electronic structures of M-N-Cs and further correlate these structures with improved electrocatalytic performances, providing an in-depth understanding of M-N-Cs at the atomic level. Finally, to promote the practical application of M-N-Cs in clean and renewable energy conversion and storage technologies, some remaining challenges and future opportunities are pointed out. A focused review is presented to comprehensively summarize the reported electronic structure modulation strategies for achieving highly active M-N-C electrocatalysts.