Reactions of adsorbed hydrogen peroxide on Ag, Au and Pt noble-metal surfaces

Hydrogen peroxide is a compound whose importance spans from biology to industry and to advanced oxidation processes. The detailed knowledge of the surface reactions of adsorbed H₂O₂ on metal surfaces is necessary for the design of its catalytic production and applications. DFT calculations are employed to study the surface reactions of H₂O₂ on noble metal surfaces of Ag, Au, and Pt. The surface de-protonation reactions and the surface pK_a (*pK_a) of H₂O₂, HO₂^– and OH. on these metals are explored for the first time. Surface de-protonation of H₂O₂ is mainly observed on the Au surface, direct O-O dissociation is preferred for Ag and the existence of both reaction channels is observed on Pt. The slow H₂O₂ surface reactions on the Au surface are found to be due to the change in reaction mechanism compared to the other metals. Even though similar products are formed on these metal surfaces upon H₂O₂ adsorption, the reaction steps and their rates are unique for each metal surface. The electron donation ability of metal surfaces is crucial in the differences in adsorption and surface reactions of radicals on each metal. As Ag is a better electron donor than Au and Pt, the mechanism of the surface reaction of H₂O₂ on Ag differs significantly from the mechanism on the two other metals. The results point out that radicals adsorbed on metal surfaces have very different chemical properties from those of them in homogeneous media.