Hydrogen peroxide electrochemistry on platinum: towards understanding the oxygen reduction reaction mechanism

Abstract

Understanding the hydrogen peroxide electrochemistry on platinum can provide information about the oxygen reduction reaction mechanism, whether H₂O₂ participates as an intermediate or not. The H₂O₂ oxidation and reduction reaction on polycrystalline platinum is a diffusion-limited reaction in 0.1 M HClO₄. The applied potential determines the Pt surface state, which is then decisive for the direction of the reaction: when H₂O₂ interacts with reduced surface sites it decomposes producing adsorbed OH species; when it interacts with oxidized Pt sites then H₂O₂ is oxidized to O₂ by reducing the surface. Electronic structure calculations indicate that the activation energies of both processes are low at room temperature. The H₂O₂ reduction and oxidation reactions can therefore be utilized for monitoring the potential-dependent oxidation of the platinum surface. In particular, the potential at which the hydrogen peroxide reduction and oxidation reactions are equally likely to occur reflects the intrinsic affinity of the platinum surface for oxygenated species. This potential can be experimentally determined as the crossing-point of linear potential sweeps in the positive direction for different rotation rates, hereby defined as the “ORR-corrected mixed potential” (c-MP).