Rutile RuO2 has remarkable activity and low overpotential for the oxygen evolution reaction (OER) and is considered a benchmark catalyst for industrial electrolysis and supercapacitors. Understanding the interaction between water and RuO2 surfaces is crucial to control the catalytic activity for OER and realize its large pseudocapacitance in the electrochemically stable potential window of water. However, there is a lack of fundamental understanding of the active sites and atomic scale processes occurring at the oxide-electrolyte interface upon interaction with water since previous work has been confined to the ultra high vacuum environment, and to the thermodynamically stable (110) surface. In this work, we use ambient pressure X-ray photoelectron spectroscopy, in situ surface diffraction and density functional theory calculations to investigate how different facets interact with water in electrochemical environments. Under electrochemical conditions, we observe that the positions of the surface Ru and O atoms are largely unchanged from 0.5 V to 1.5 V versus the reversible hydrogen electrode (RHE) scale while adsorbed water molecules on the co-ordinatively unsaturated site (CUS) are deprotonated gradually with increasing potential. We find that the water dissociation ability is sensitive to the surface crystallographic orientation – being maximum for the (101) surface, followed by the (110), (001) and (100) surfaces. At oxygen evolution potentials, we observe the formation of an –OO like group on the CUS site for the (110) and (100) orientations, while this intermediate is energetically unfavorable and is not observed at high potentials for the (101) and (001) surfaces due to the weaker binding of oxygen on these surfaces. By using different experimental and theoretical techniques on model surfaces, this study identifies the active sites for oxygen electrocatalysis and demonstrates the role of local coordination interactions on the OER mechanism and activity.

Understanding the active sites and reaction mechanism for oxygen electrocatalysis on ruthenium dioxide surfaces

256th National Meeting (2018)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.