Nanocarbon for Oxygen Reduction Electrocatalysis: Dopants, Edges, and Defects

The oxygen reduction reaction (ORR) is the cornerstone of various sustainable energy‐conversion technologies. Metal‐free nanocarbon electrocatalysts with competitive activity, enhanced durability, and satisfactory cost, have been proposed as the most promising substitute for precious‐metal catalysts. However, their further development is still primarily based on trial‐and‐error approaches due to the controversial knowledge of critical active sites and mechanisms. Herein, the activity origins of nanocarbon‐based ORR electro­catalysts are comprehensively reviewed and correlated, considering the dopants, edges, and defects. Analogously, they can effectively modify the charge/spin distribution on the sp 2 ‐conjugated carbon matrix, leading to optimized intermediate chemisorption and facilitated electron transfer. Specific doping at defective edges is expected to render practical applications for metal‐free nanocarbon electrocatalysts.