Non‐N‐Doped Carbons as Metal‐Free Electrocatalysts

Ten years have passed since the discovery of the first nitrogen-doped carbon-based metal-free catalyst for the oxygen reduction reaction, which opened a new field of catalysis toward a large variety of important applications, ranging from energy conversion and storage to environmental remediation. Various heteroatom-doped carbons, beyond nitrogen-doping (N-doping), with distinctive features have also been developed for many specific reactions of practical significance (e.g., oxygen reduction (ORR), water splitting (OER and HER), CO2 reduction (CO2RR), and N2 reduction (NRR)). However, the topic of metal-free non-N-doped carbon electrocatalysts has not been reviewed till now. This article aims to review recent advances in non-N-doped carbon electrocatalysts with an emphasis on their synthesis, catalytic mechanisms, and catalytic performance in various electrochemical reactions, including the ORR, OER, HER, H2O2 production, NRR, and CO2RR. Like N-doping, boron-doping, phosphorus-doping, and fluorine-doping are found to show similar catalytic efficiency for the ORR, OER, and HER. However, oxygen-doping and boron-doping are particularly favorable for the selective production of H2O2 and NH3, respectively, exceeding the performance of N-doping. Along with the timely and critical overview on the non-N-doped carbon electrocatalysts, current challenges and future perspectives for this emerging field are also discussed.