Catalytic and electrocatalytic activity of Pt-Ru/C electrode for hydrogen oxidation in alkaline and acid aqueous electrolytes: EMSI and EPOC effects

Abstract

The kinetics of the oxidation of H2 on PtRu/C gas-diffusion electrode was studied by interfacing the electrode with aqueous electrolytes at different pH values. The conducting electrolytes were KOH and HCIO4 aqueous solutions with different concentrations. It is shown that the nature of the aqueous electrolyte plays the role of an active catalyst support for the PtRu/C electrode which drastically affects its catalytic properties. During the aforementioned interaction, termed electrochemical metal support interaction (EMSI), the electrochemical potential of the electrons at the catalyst Fermi level is equalised with the electrochemical potential of the solvated electron in the aqueous electrolyte. The electrochemical experiments carried out at various pH values showed that the electrochemical promotion catalysis (EPOC) is more intense when the catalyst-electrode is interfaced with electrolytes with high pH. values where the OH ionic conduction prevails. It was concluded that similar to the solid state electrochemical systems EPOC proceeds through the formation of a polar adsorbed promoting layer of OHadδ-, electrochemically supplied by the OH species, at the three phase boundaries of the gas exposed gas diffusion catalyst-electrode surface.