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 AgxInyS(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 S2- 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 H-2 production among those AgxInyS(x+3y/2) products, and the higher crystallinity and fewer defects of the AgIn5S8 octahedrons compared to the other AgxInyS(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 H-2 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 H-2 production.