Exploiting dynamic water structure and structural sensitivity for nanoscale electrocatalyst design

Abstract

The anomalous pH dependence of the hydrogen evolution (HER) and oxidation (HOR) reactions limits both fundamental science and material design for electrocatalytic systems in alkaline environments. Here we demonstrate the impact of Ru(OH)x surface decoration on the HER/HOR activity of Pt single crystals and nanocatalysts, and present evidence correlating this improvement in activity to a negative shift in the potential of zero charge (Epzc). Proximity of the Epzc and reaction reversible potential dictates lower transition state barriers yielding a more facile H/OH exchange and improved reaction kinetics. The effect of the surface decoration is found to be structurally sensitive to the atomic geometry of the underlying Pt substrate. Applying this structural sensitivity to catalyst design, rotating disk voltammetry of Ru(OH)x decorated Pt nano-octahedra (Octa-Pt/C) demonstrates negligible HOR overpotential and a HER overpotential of ~50 mV at a current density of 10 mA/cm2.