Oxygen Evolution on MoS2 Edges: Activation through Surface Oxidation

The catalytic activity of zigzag (ZZ) edges of MoS2 with different surface sulfur coverages for the oxygen evolution reaction (OER) is studied using ab initio molecular dynamics simulations and hybrid explicit/implicit descriptions of the embedding aqueous medium. Following electrochemical adsorption of oxygen species, ZZ edges with S-coverage are found to undergo surface oxidation that significantly reduces the percentage of S-coverage under applied oxidative potential. The most stable morphology at the relevant potential for oxygen evolution corresponds to the oxygenated ZZ-Mo-edge with 0% S-coverage. Depending upon the reaction site, different concerted catalytic pathways are observed on this edge, with minimum thermodynamic overpotential values varying between 0.5 and 0.8 V. By performing a systematic exploration of the edge reactivity, optimal two-site catalytic pathways are observed, for which the OER overpotentials are found to be considerably reduced compared to the basal plane and S-covered ZZ edges.