Hierarchical CoS@InS Heterojunction for Efficient Photocatalytic Reduction of CO to Syngas.

Photocatalytic reduction of CO to solar fuels is recognized as a promising route to address environmental and energy issues. However, there exist two challenges of insufficient CO activation and fast charge carrier recombination, impeding this conversion. Herein, a hierarchical CoS@InS (CoS@InS) heterojunction is developed by the in situ growth of the InS nanosheets on the CoS nanotubes for efficient photocatalytic reduction of CO to syngas in an aqueous reaction system with [Ru(bpy)]Cl serving as a photosensitizer and triethanolamine as a sacrificial agent. In addition to the promoted charge separation and transfer, the strong interfacial electric field formed in this heterojunction tunes the p-band center of In active sites toward the Fermi level. Accordingly, the adsorption of the key intermediate *COOH is enhanced, and the energy barrier of *CO desorption is reduced. Besides, the hierarchical hollow structure enhances light utilization and mass transfer, increases the specific surface area, and provides abundant reaction sites. As a result, the hierarchical CoS@InS heterojunction exhibits superior activity. The optimized heterojunction yields CO and H production rates as high as 83,648 and 28,635 μmol g h, respectively, with an apparent quantum yield of 5.60% at 450 nm.