Semiconductor effect on the selective photocatalytic reaction of .alpha.-hydroxycarboxylic acids

• DOI: 10.1021/j100341a070
• Publication Date: 2005-03-14T23:57:54Z
• Authors: H. Harada; T. Sakata; T. Ueda
• Keywords: 01 natural sciences; 0104 chemical sciences

Photocatalytic and photoelectrochemical reactions of {alpha}-hydroxycarboxylic acids were compared for various types of semiconductor electrode (TiO{sub 2}, CdS, SrTiO{sub 3}, and ZnO) and suspension of particulate semiconductor (TiO{sub 2}, CdS, MoS{sub 2}, 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/TiO{sub 2}, decarboxylation took place in addition to dehydrogenation. The same dependence was observed in the photoelectrochemical reactions with semiconductor single-crystal electrodes. For the TiO{sub 2} electrode, the reaction depends strongly on pH, whereas it does not for CdS. The results of pH effects, electrochemical reaction with various 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.