Electrochemical promotion of propane oxidation at Pt/BiCuVOx-YSZ thin-film cells: Economical use of YSZ

Abstract

Abstract Electrochemical promotion of catalysis (EPOC) or Non-faradaic electrochemical modification of catalytic activity (NEMCA) is a phenomenon that may be exploited in catalytic converters to reduce the usage of precious metal catalysts. Nevertheless, the conventional structure of NEMCA cells employs a thick piece of relatively expensive solid electrolyte such as yttria-stabilised zirconia (YSZ). Minimising the amount of this costly material may bring EPOC closer to commercial application. NEMCA cells were fabricated with thin films of YSZ or BiCuVOx-YSZ as the electrolytes and sputtered Pt as the working catalyst electrodes. The catalytic activity for propane combustion was studied at 200, 300, 400, and 500 °C for cells with YSZ, but only at 400 °C for cells with BiCuVOx-YSZ. The effects of working electrode potentials and BiCuVOx contents were also studied. Most cells made with only YSZ could not function as electrochemical cells. Nevertheless, only one cell survived and exhibited NEMCA. On the other hand, all BiCuVOx-YSZ cells functioned properly. Electrophobic NEMCA behaviour was observed from both cell types. Addition of BiCuVOx improved sintering and resulted in films of higher conductivity. Nonetheless, diminished surface areas and suppressed faradaic efficiencies were observed. Undesirable electronic conductivity was also introduced by BiCuVOx and hence an optimum BiCuVOx content of 3.5 wt % was observed to offer the highest rate enhancement ratio, ρ, and the highest faradaic efficiency, Λ, of 5.3 and 339, respectively, at 400 °C.