Electro-Oxidation of Glycerol to Formate at Near-Zero Potential Driven by Cathodic Oxygen Reduction-Generated *OH.

Electrochemical oxidation of glycerol to formate via C─C bond cleavage has emerged as an attractive technology for the conversion of surplus glycerol into diverse high-value chemicals; yet the performance is limited by the high anodic potential as the reaction typically follows the oxygen evolution reaction (OER)-coupled pathway. In this study, we demonstrate that glycerol oxidation to formate can be mediated by the cathodic oxygen reduction reaction (ORR) instead at near-zero potential. Among the model catalysts with different ORR selectivity, oxygen-doped carbon (O-CNP) stands out as the best catalyst for glycerol oxidation with 91.0% formate selectivity, producing 246 mM formate at -0.3 V versus RHE after 8 h. Such a performance is comparable to that with state-of-the art OER-coupled strategy operated at potentials over +1.3 V versus RHE. The selective glycerol oxidation at low cathodic potentials is driven by the active *OH species generated during ORR, as evidenced by in situ spectroscopy and radical quantification and quenching experiments. Computational studies reveal that the generation of *OH and the mediation in glycerol oxidation are thermodynamically favorable on O-CNP as compared to others in the series. This work paves a new avenue for glycerol oxidation via cathodic reactive oxygen species mediation.