Intrinsic carbon structural imperfections for enhancing energy conversion electrocatalysts

Carbon-based metal-free electrocatalysts have been placed with great expectations since their very first emergence. As a promising alternative to the noble metal-based counterparts, significant advancements have been made in this exciting research field. Sizable amounts of efforts have been devoted to understanding the function and mechanism of metalloid dopants. It is believed that dopants induce asymmetric distribution of charge/spin densities, turning adjoining carbon atoms into catalytically active sites. However, the intrinsic structural imperfections/defects that ubiquitously exist in carbon materials have recently been demonstrated to outperform dopants in enhancing the catalytic properties of carbon catalysts. This new source of activity contributor has thus triggered considerable attention to dopant-free defect-rich carbon electrocatalysts. To follow up recent progress, we present a state-of-the-art and systematic overview specifically focusing on the critical role of intrinsic structural defects in dopant-free carbon electrocatalysts for energy conversion applications. Various aspects in terms of definition, characterization, function, and catalytic mechanism of structural defects are thoroughly covered together with some shared perspectives on the future opportunities. We hope this contribution will inspire more efforts in this fascinating direction and push forward the further development of carbon-based electrocatalysts.