Electrochemical promotion of methane oxidation over nanodispersed Pd/Co3O4 catalysts

During the last two decades the Electrochemical Promotion of Catalysis (EPOC) phenomenon has been studied extensively for many catalytic reactions including hydrocarbon oxidation reactions and hydrogenations. In the majority of the studies, the catalysts/electrodes consisted of porous noble metal films (Pt, Pd, Rh) prepared, for instance, by calcination of organometallic pastes. This results in low metal dispersion and low active surface area, limiting therefore the overall catalytic activity. In view of further practical application of the EPOC phenomenon to industrial catalysts, we should be able to enhance the activity of nanodispersed materials. In this study, for the very first time, we observed an enhanced catalytic activity of a Pd nanodispersed catalyst supported on a porous Co3O4 semiconductor film. The Pd/Co3O4 composite powder was deposited on an yttria-stabilized zirconia (YSZ) solid electrolyte without the presence of an interlayer film. The observed enhancement was non-Faradaic, with Faradaic efficiency values as high as 80. The Pd/Co3O4 catalyst was characterized thoroughly by means of a wide variety of physicochemical techniques, such as TEM, SEM, TGA, ICP and BET. In addition, this material was further compared with a classical Pd/YSZ metallic film, prepared by calcination of an organometallic paste. This allows for a comparison of metal-support interactions (MSI) and the EPOC effect. Using supported catalysts as catalytic films for electrochemical promotion studies may lead to the practical utilization of EPOC in the chemical industry or in gas exhaust treatment.