Semiconductor Effect on the Selective Photocatalytic Reaction of α-Hydroxycarboxylic Acids

Article abstract of DOI:10.1021/j100341a070

Photocatalytic and photoelectrochemical reactions of α-hydroxycarboxylic acids were compared for various types of semiconductor electrode (TiO2, CdS, SrTiO3, and ZnO) and suspension of particulate semiconductor (TiO2, CdS, MoS2, and ZnS).These reactions were found to depend strongly on the type of semiconductor studied.In the cases of Pt/CdS and ZnS photocatalysts, the hydroxy group of the acids was oxidized selectively into the corresponding keto acids, whereas in the cases of Pt/TiO2,decarboxylation took place in addition to dehydrogenation.The same dependence was observed in the photoelectrochemical reactions with semiconductor single crystal electrodes.For the TiO2 electrode, the reaction depends strongly on pH, whereas it does not for CdS.The results of pH effects, electrochemical reaction with metal electrodes, and Fenton reaction in a homogeneous solution suggest the importance of adsorption of the reactants on the semiconductor and metal surfaces for the selective reaction.