Abstract
Understanding oxygen reduction, key to much of electrochemical energy transformation technology, crucially requires exploration of the role of hydrogen peroxide as a possible intermediate especially on catalysts such as Pt which can bring about the 4e reduction of O(2) to water. We reveal that at the single nanoparticle scale the direct platinum catalysed reduction of hydrogen peroxide is found - even at high overpotentials - not to be controlled by the rate mass-transport of the reagents to the interface but by a surface limited process. Further under alkaline (pH 12.3) and near mass-transport free conditions, the single nanoparticle hydrogen peroxide reduction rate goes through a maximum at potentials comparable to the surface deposition of hydrogen (H (upd)) with the highest reaction rate occurring when the surface is partially covered in hydrogen.