Role of rhodium anode in the YSZ-aided CH4 oxidation into syngas

Direct partial oxidation of CH4 into synthesis gas has been studied by using an Rh|YSZ|Ag electrochemical reactor. Oxygen was pumped from the Ag cathode to the Rh anode through the YSZ to produce adsorbed oxygen species on the surface of the Rh anode. The adsorbed oxygen species can oxidize CH4 to CO/H2 directly, i.e. not via combustion of CH4 to CO2 and H2O followed by the reforming reactions of CH4 with CO2 and H2O. The oxygen pumping treatment through the YSZ affected significantly the surface morphology of the Rh anode. A three-dimensional network consisting of fine Rh particles was formed by the oxygen pumping treatment, resulting in an enhanced migration of oxygen species from the triple-phase boundary to the Rh anode surface of high surface area. Thus, an enormous increase in the production of CO/H2 by the direct partial oxidation of CH4 was observed over the Rh anode treated by the oxygen pumping.