Sustainable H2 gas production by photocatalysis

The photocatalytic, ambient temperature, reforming of oxy-hydrocarbons, used to generate hydrogen gas, has been studied in some detail over Pd-titania systems and a general mechanism is developed. In the case of water–methanol mixtures, methanol adsorption on the metal surface results in hydrogen gas evolution and the formation of adsorbed CO. The latter is subsequently oxidised by an oxygen species (O−) generated in the semiconductor by UV light. Desorption of the resulting CO2 enables another methanol molecule to adsorb, restarting the cycle. Water is reduced at the titania hole replacing the lost anion and generating further hydrogen. We will discuss the evidence for this mechanism and extend it to consider the photocatalysis of higher alcohols including ethanol, butanol and glycerol.