Hierarchical Co<sub>9</sub>S<sub>8</sub>@In<sub>2.77</sub>S<sub>4</sub> Heterojunction for Efficient Photocatalytic Reduction of CO<sub>2</sub> to Syngas
Hang Zhao, Hao Song, Zhefei Pan, Xun Zhu, Dingding Ye, Yang Yang, Hong Wang, Rong Chen, Qiang Liao
Abstract
Photocatalytic reduction of CO 2 to solar fuels is recognized as a promising route to address environmental and energy issues. However, there exist two challenges of insufficient CO 2 activation and fast charge carrier recombination, impeding this conversion. Herein, a hierarchical Co 9 S 8 @In 2.77 S 4 (CoS@InS) heterojunction is developed by the in situ growth of the In 2.77 S 4 nanosheets on the Co 9 S 8 nanotubes for efficient photocatalytic reduction of CO 2 to syngas in an aqueous reaction system with [Ru(bpy) 3 ]Cl 2 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 2 production rates as high as 83,648 and 28,635 μmol g –1 h –1, respectively, with an apparent quantum yield of 5.60% at 450 nm.