Recent advances of doped carbon as non-precious catalysts for oxygen reduction reaction

Owing to their remarkable catalytic activities, doped nanocarbon materials have been widely employed as efficient noble metal-free catalysts for oxygen reduction reaction (ORR) towards the artificial energy conversion systems, such as fuel cells and a variety of sensors. After several decades of innovative investigation, the substantial controversies still exist ranging from synthesis strategies to actual active sites for doped nanocarbon materials, but greatly pave the development of sustainable ORR electrocatalysts with high efficiency. This review mainly focuses on the newly developed synthesis methods, such as ball milling, co-doping with multi-elements and low temperature preparation with more predictable structures that were reported in the last five years. Particularly, we have also discussed the open controversies and mechanism studies of doped carbon for ORR.