THE PHOTOREDUCTION OF ACETYLENE BY BAND-GAP IRRADIATION OF TIO2 USINGMO2O4(DIETHYLDITHIOCARBAMATE)(2) AS A CATALYST

The photoreduction of acetylene is catalyzed by Mo2O4(dedtc)(2) (dedtc , diethyldithiocarbamate) in the presence of 5-8 nm diameter colloidal TiO2. This photocatalytic process exhibits optimum activity at pH 6 a nd a loading of 30 catalyst molecules per TiO2 particle. The same cata lytic site(s) are responsible for C2H2 reduction to C2H4 and C2H6 and H+ reduction to H-2. The overall photonic efficiency is 1.3% for the t ransfer of reducing equivalents to products at full lamp intensity, an d increases with decreasing intensity. The effects of pH, temperature, intensity and loading on the catalytic process are consistent with a mechanism in which the catalytic site associated with the TiO, surface promotes the transfer of H atoms or electrons to the bound substrate. The photocatalytic properties of this neutral molecular complex are c ompared with those observed for other Mo-containing catalysts. (C) 199 7 Elsevier Science S.A.