Stability and Solvation of Key Intermediates of Oxygen Evolution on TiO2, RuO2, IrO2 (110) Surfaces: A Comparative DFT Study

Oxygen Evolution Reaction (OER) is a fundamental process, with gold standards like RuO2 and IrO2. Recently, it was suggested that OER could go through unconventional intermediates, −O−H, −OO−H. −O−H is formed by the direct interaction of an adsorbed O species to a metal surface atom and a proton bound to a surface oxygen. Similarly, in −OO−H, an adsorbed −OO adduct interacts with a proton on a surface oxygen. This work compares the nature of key intermediates of OER on TiO2, RuO2, and IrO2(110) surfaces by Density Functional Theory (DFT) calculations and Ab-Initio Molecular Dynamics (AIMD). We rationalized the nature, the relative stability trends in vacuum and the effect of water solvation of the species. −OO−H is preferred than −OOH. −OH is preferred than −O−H except for RuO2. We investigated the nature of the catalyst/water interfaces and the interaction of intermediates with water based on AIMD. On RuO2, −OH and −O−H display a different interaction with water. −OO−H is quite rigid on RuO2, while it is dynamic on IrO2 as the proton is shared between −OO and a surface oxygen atom. This study provides insights on the role of solvation to the nature of OER intermediates, that may help future studies.