Influence of Local Inhomogeneities and the Electrochemical Environment on the Oxygen Reduction Reaction on Pt-Based Electrodes: A DFT Study

We have performed density functional theory calculations to explore the possibility to overcome the linear scaling relations in the oxygen reduction reaction (ORR) using local inhomogeneities on Pt-based surface alloys, supported Pt monolayers, and Pt islands. We demonstrate that invoking inequivalent neighboring reaction sites allows overcoming the restrictions of one-dimensional linear scaling relations. As a consequence, the ORR activity at a (111) edge site of a Pt island on a Ru(0001) substrate outperforms the one on flat Pt(111). Furthermore, we show that it is critical to appropriately take the electrochemical environment into account, including the proper surface coverage and the presence of the electrolyte, which leads to microscopically modified ORR reaction schemes and a redetermination of the rate-limiting step.