Molecular Co2+ ions were grafted onto doped graphene in a coordination environment, which resulted in formation of molecularly well-defined electrocatalytic sites at heterogeneous interface for oxygen evolution reaction (OER). The S dopants of graphene were suggested as one of the binding sites and responsible for improving the intrinsic activity of Co sites. Electrochemical studies showed that the Co2+ ions were successively oxidized to Co3+ and Co4+ states prior to OER. The sequential oxidation was coupled with transferring different numbers of protons/hydroxides and generated an active Co4+=O fragment. A side-on hydroperoxo ligand of Co4+ site was proposed to be a key intermediate toward the formation of dioxygen. The research is now published in J. Am. Chem. Soc., 2017, 139 (5), pp 1878–1884, DOI: 10.1021/jacs.6b10307.

Reporter: Wei Xiao