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.