Ag nanocluster loading effect an TiO2 photocatalytic reduction of bis(2-dipyridyl)disulfide to 2-mercaptopyridine by H2O

An efficient endothermic reduction of bis(2-dipyridyl)disulfide (RSSR) to 2-mercaptopyridine by H2O has been found to proceed selectively using TiO2 as a photocatalyst. With 0.24 wt % loading of Ag nanoclusters (<1 nm) on TiO2, the reduction was significantly enhanced concomitantly by a 17.9-fold increase in the saturated adsorption amount of RSSR due to specific Ag-S interaction. A reaction mechanism involving H2O oxidation as the rate-determining step is proposed on the basis of adsorption and kinetic data analyses. In this reaction system, the respective adsorption of the oxidant (RSSR) on the reduction sites (Ag) and the reductant (H2O) on the oxidation sites (TiO2) is realized. The reaction-promoting effect of the Ag loading can be attributed to this selective adsorption as well as the increases in the adsorption amount and the efficiency of charge separation.