Preparation of Single-Crystalline AgIn₅S₈ Octahedrons with Exposed {111} Facets and Its Visible-Light-Responsive Photocatalytic H₂ Production Activity

Although AgIn₅S₈ as one kind of ternary chalcogenides has been extensively investigated due to its band-edge positions meeting the thermodynamic requirement for water photosplitting, very little attention has been focused on the crystallinity and facet effects of AgIn₅S₈ on its photocatalytic activity. Herein, a facile hydrothermal route was developed to fabricate regular single-crystalline AgIn₅S₈ octahedrons with only {111} facets exposed. Also, the effects of the hydrothermal reaction conditions on the composition, crystal phase, crystallinity, and morphology of the obtained Ag_xIn_yS_(x+3y/2) products (hereafter denoted as AIS-x, where x represents the pH value of the reaction solution) were investigated, and it was found that the accurately released S^2– ions from the thermal decomposition of thioacetamide (TAA) is the central factor for the nucleation and growth of the AgIn₅S₈ octahedrons. The experimental results indicate that the resultant regular AgIn₅S₈ octahedrons (AIS-10.6) exhibit the best photocatalytic activity for H₂ production among those Ag_xIn_yS_(x+3y/2) products, and the higher crystallinity and fewer defects of the AgIn₅S₈ octahedrons compared to the other Ag_xIn_yS_(x+3y/2) products can retard the photogenerated charge recombination, while those indium atoms with higher density in the exposed {111} facets might be beneficial for the photocatalytic H₂ production reaction by acting as active sites to promote the charge separation and transfer processes. The results presented here provide new insights into the significance of crystallinity and exposed facets in the visible-light-responsive activity of AgIn₅S₈, thus paving new ways into the design and synthesis of high-performance, cost-effective AgIn₅S₈ photocatalysts for H₂ production.