Measurements of Oxygen Electroadsorption Energies and Oxygen Evolution Reaction on RuO(110): A Discussion of the Sabatier Principle and Its Role in Electrocatalysis.

We report the hydroxide (OH) and oxide (O) experimental electroadsorption free energies, their dependences on pH, and their correlations to the oxygen evolution reaction (OER) electrocatalysis on RuO(110) surface. The Sabatier principle predicts that catalyst is most active when the intermediate stabilization is moderate, not too strong such that the bound intermediate disrupts the subsequent catalytic cycle, nor too weak such that the surface is ineffective. For decades, researchers have used this concept to rationalize the activity trend of many OER electrocatalysts including RuO, which is among the state-of-the-art OER catalysts. In this article, we report an experimental assessment of the Sabatier principle by comparing the oxygen electroadsorption energy to the OER electrocatalysis for the first time on RuO. We find that the OH and O electroadsorption energies on RuO(110) depend on pH and obey the scaling relation. However, we did not observe a direct correlation between the OH and O electroadsorption energies and the OER activity in the comparative analysis that includes both RuO(110) and IrO(110). Our result raises a question of whether the Sabatier principle can describe highly active electrocatalysts, where the kinetic aspects may influence the electrocatalysis more strongly than the electroadsorption energy, which captures only the thermodynamics of the intermediates and not yet kinetics.