A Theoretical Investigation into the Role of Surface Defects for Oxygen Evolution on RuO₂

The inability of conventional theoretical models to corroborate the well-known experimental activity of RuO₂ for the oxygen evolution reaction (OER) has recently been the subject of numerous research efforts. In this study, we use density functional theory calculations to investigate the possibility that surface defects formed during dissolution are responsible for the OER activity of RuO₂. It has been well-established experimentally that RuO₂ undergoes dissolution during OER, yet little is known about the atomic structure or catalytic reactivity of the resulting defect sites. Through simulation of point defects, steps, and kinks derived from the RuO₂ (110) surface, we discover a 0.7 eV range in the primary descriptor for OER activity, with the most active sites outperforming those at the ideal (110) surface by nearly 0.5 eV. We postulate that these variations in reactivity are due to differences in the local electronic structure, and we investigate in more detail the electronic structure of two singly coordinated sites at the same Ru atom located at a kink. Finally, we investigate possible dissolution pathways that may proceed at the RuO₂ surface under OER conditions.