Interplay of Corrosion and Photocatalysis During Nonaqueous Benzylamine Oxidation on Cadmium Sulfide

Abstract

The photo(electro)chemical properties of bulk, nanowire, and chemical bath deposits of cadmium sulfide (CdS) for benzylamine oxidation to N-benzylidenebenzylamine (N-BB) in acetonitrile have been evaluated as a model for the activity and stability of CdS toward selective organic oxidations. CdS photocatalysts selectively deliver N-BB at rates ranging from 5 to 26 mM h–1. Although CdS is a capable photocatalyst, SEM imaging and XPS analysis reveal significant morphological and compositional changes to the particles upon photolysis in benzylamine. These surface changes and surface sulfide oxidation are accompanied by Cd2+ leaching and hydrogen sulfide evolution, highlighting both redox and acid–base pathways of nonaqueous CdS corrosion. All facets of corrosion have been linked directly with amine reactivity, as the CdS particles are unaffected by substrate-free photolysis. A series of experiments using N,N-dimethylbenzylamine, 4-N,N-trimethylaniline, and ferrocene show that nonaqueous CdS corrosion is facilitated by acidic reaction intermediates opposed to photogenerated holes. Additionally, water and oxygen are essential components to corrosion, as photoelectrochemistry under dry/air-free conditions displays higher and stable photocurrent density as well as material stability. Finally, CdS nanowires display improved corrosion resistance, suggesting that control of particle morphology and/or electronic structure is essential for developing novel chalcogenide photocatalysts.