In situ X-ray-electrochemical studies on the origin of H 2O 2 production during oxygen reduction at transition metal cluster materials

Abstract

It was found that during the electrochemical reduction of molecular oxygen in acidic medium the ternary cluster materials (M x Mo 6S 8; M: Ag, Ba, Cd, Zn, Sn, Pb, In) produce 4% H 2O 2 and the Pd-containing cluster material produces 8% H 2O 2 when their surface is free from oxides. Since, eg, Ag metal produces H 2O 2 with 60% efficiency this result proves that the multi-electron charge transfer is carried out mainly via the Mo 6-cluster which functions as the reaction centre. Hydrogen peroxide production is enhanced parallel with the oxidation of the cluster material surface. This process enriches the supported cluster electrode in oxides originating from the cluster matrix itself and from the metal excalated from the material. This phenomenon of oxidative stimulation of H 2O 2 generation was shown with an in situ X-ray probe.