Selective H₂O₂ electrosynthesis by O-doped and transition-metal-O-doped carbon cathodes via O₂ electroreduction: A critical review

Hydrogen peroxide (H₂O₂) electrosynthesis via the oxygen reduction reaction (ORR) presents an attractive decentralized alternative to the industry-dominant anthraquinone process. Oxidized carbon materials have proven to be promising catalysts due to their low cost and facile synthesis procedures. However, the nature of the active sites is still controversial. The objective of this paper is to provide a critical review of the advances of this topic. The fundamentals of the ORR pathway and O-doping effects are described, followed by the experimental preparation methods for O-doped carbon, including chemical oxidation and electrochemical oxidation. To identify the contribution of each oxygen-containing functional group (OG) or combination of OGs towards 2-electron ORR, combined experimental and DFT calculation results were analyzed. This paper also reviews the new advancement in the co-doping of O and transition metals, which could realize high activity and high selectivity toward H₂O₂ generation. Future directions in this fascinating field are also highlighted.