Photocatalytic Hydrogen Evolution Coupled with Efficient Selective Benzaldehyde Production from Benzyl Alcohol Aqueous Solution over ZnS-Ni_<i>x</i>S_<i>y</i> Composites

Abstract

Photocatalytic hydroxy group transformation to carbonyl is an important application in organic chemistry. It seems challenging to acquire great selectivity toward carbonyl products in green water solution, especially for the wide-bandgap semiconductors which always need to seek assistance from organic media like acetonitrile. Herein, we cast off the dependence on such organic solvents and develop an efficient NixSy modification on ZnS nanorods, for selective oxidation of benzyl alcohols coupled with H2 evolution in anaerobic water. The ternary augmentation in H2 production, alcohol conversion, and, more strikingly, benzaldehyde selectivity (from 8.1% to 90.5%) was simultaneously achieved by loading NixSy cocatalysts. Mechanism investigations indicated a striking transformation from hole-predominant oxidation on ZnS surface to an electron-initiating dehydrogenation of alcohols on NixSy nanoparticles. Besides, NixSy nanoparticles tend to swiftly desorb the produced benzaldehyde, thereby resulting in promoted selectivity. Particularly, the catalysts performed much greater benzyl alcohol transformation efficiency in corresponding aqueous solution than they did in acetonitrile, where little aldehyde remained. Overall, the study reveals the inspiring roles of NixSy as a selective dehydrogenation unit and a hydrogen evolution cocatalyst, therefore enabling ZnS in efficient selective benzyl alcohol transformation coupled with hydrogen evolution in green aqueous solution.