Atomistic insights into Cl^--triggered highly selective ethylene electrochemical oxidation to epoxide on RuO₂: Unexpected role of the in situ generated intermediate to achieve active site isolation

Electrochemical partial oxidation of hydrocarbons to value-added products using electricity from renewable energy resources has the potential to change the way that commodity chemicals are manufactured. In this study, we used density functional theory calculations combined with a constant electrode potential model to study the previously reported ethylene partial electro-oxidation to epoxide on RuO₂(110) in an aqueous solution containing [Cl^-] = 0.3 M. We found that the high selectivity toward epoxide is due to the in situ generated *OCClO* intermediate that blocks parts of the surface and leads to isolation of *O (surface adsorbed oxygen) active sites. This step turns off the pathways to over-oxidation and drives the reaction toward epoxide formation. The reaction mechanisms for ethylene over-oxidation and partial oxidation are proposed. Our theoretical study unveiled a dynamic and unique means to achieve active site isolation that can be used to improve selectivity of hydrocarbon partial electro-oxidation.