Photocatalytic Reforming of Aqueous Acetic Acid into Molecular Hydrogen and Hydrocarbons over Co-catalyst-Loaded TiO2: Shifting the Product Distribution

Acetic acid in aqueous suspensions of co catalyst-loaded TiO2 was photocatalytically converted into carbon dioxide, molecular hydrogen, methane, and ethane. The formed amounts of CO2 were found to increase in the order Ag/TiO2 < Au/TiO2 < Rh/TiO2 < RuO2/TiO2 < IrO2/TiO2 < Pt/TiO2, thus indicating that the metal oxides employed here are suitable co-catalysts to promote the photocatalytic conversion of acetic acid. The same sequence of activities was found for methane evolution but not for the formation of H-2. The evolved amounts of these products as well as the amount distribution were found to be strongly affected by the initial concentration of the organic acid and by the co-catalyst. A large value of the work function of the employed co-catalyst seems to favor H-2 evolution. Gaseous mixtures rich in hydrocarbons are photocatalytically produced at sufficiently high initial concentrations of acetic acid employing a composite photocatalyst, where the co-catalyst has a low value of the work function, such as IrO2 and Ag.