ZnIn₂S₄ Nanosheet Arrays on Co₉S₈ Hollow Nanotubes for the Photoredox Coupling of Benzyl Alcohol Oxidation with H₂ Evolution

Combining hydrogen evolution with the conversion of benzyl alcohol (BA) into benzaldehyde (BAD) could provide an alternative pathway for sufficiently utilizing photogenerated electrons and holes to achieve high value chemicals and fuels. Herein, a ZnIn2S4 nanosheet array/one-dimensional Co9S8 hollow nanotube (Co9S8/ZnIn2S4) composite has been fabricated by simple hydrothermal and solvent thermal methods. Without the utilization of sacrificial agents, the optimal 20%-Co9S8/ZnIn2S4 hybrid catalyst shows a superior H2 production of 3070.56 μmol·g–1·h–1 and a high benzyl alcohol conversion rate of 93.2%, which are 4.1 and 2.9 times higher than those of individual ZnIn2S4, respectively. The superior photocatalytic performance over Co9S8/ZnIn2S4 nanocomposites compared with bare ZnIn2S4 can be credited to the introduction of Co9S8 hollow nanotubes as a cocatalyst, which can offer plentiful active sites, improve the absorption of visible light, and facilitate the separation and transfer of electron–hole pairs of ZnIn2S4. Multiple cycling experiments indicate good durability of the Co9S8/ZnIn2S4 nanocomposite. In addition, the in situ electron paramagnetic resonance indicates that α-hydroxybenzyl radicals are the key intermediate of the conversion of BA into BAD. This paper is intended to provide a meaningful reference for the ingenious design of the photocatalyst structure and building a high-performance coupled photocatalytic system with sufficient utilization of electrons and holes.