The photocatalytic reforming of methanol

The anaerobic photocatalytic decomposition of methanol in aqueous solution has been investigated using a Pd/TiO2 catalyst. The rate is near zero order in methanol over most of the range of reaction, but has a complicated dependence on the loading of Pd on the photoactive support. This dependence is explained by assigning the active site for the rate determining step to be at the interface between the Pd and the TiO2. In the absence of light, the methanol does not decompose at steady state on the catalyst, probably due to poisoning of the Pd surface with adsorbed CO. Light of greater energy than the TiO2 band gap (similar to 3.2 eV) causes photoexcitation of electrons into the conduction band; this produces an oxidant which reacts with adsorbed CO to produce CO2 and hence maintains a steady state rate of methanol decomposition. The overall oxidant is water. A detailed model for the reaction is proposed. (C) 1999 Elsevier Science B.V. All rights reserved.