Semiconductor photocatalysis. I. Quantitative photoreduction of aliphatic ketones to alcohols using defect-free zinc sulfide quantum crystallites

Abstract

Quantized ZnS microcrystallites (2-5 nm) and their aggregates, which were vividly confirmed by a high-resolution electron microscope, catalyze photoredox reactions of an aqueous mixture of 2-butanone, Na{sub 2}S, and Na{sub 2}SO{sub 3} under >313-nm light irradiation; the ketone is quantitatively photoreduced to 2-butanol without much H{sub 2}, and S{sup 2{minus}} and SO{sub 3}{sup 2{minus}} ions are photooxidized to S{sub 2}O{sub 3}{sup 2{minus}} ion. The synergistic effect of S{sup 2{minus}} and SO{sub 3}{sup 2{minus}} ions and quantum size effect on the photocatalytic system are discussed in terms of spectral properties, and the selective and highly efficient photoredox reactions of this system are attributed to suppression of the formation of the localized surface states, which cause competitive water photoreduction to H{sub 2} or deactivation of the catalysts.