CdIn₂S_4‐xSe_x Solid‐Solution Nanocrystal Photocatalyst: One‐Step Hydrothermal Synthesis, Controllable Band Structure, and Improved H₂‐Evolution Activity

Abstract Metal sulfide solid‐solutions have served as one of the most promising photocatalysts due to continuously adjustable bandgap structure and light‐absorption performance. Herein, a novel quaternary CdIn₂S_4‐xSe_x solid‐solution nanocrystal photocatalyst is prepared by one‐step hydrothermal synthesis, including the initial production of CdIn₂S_4‐x(SeO₃)_x and its in situ reduction of SeO₃²⁻ to produce Se²⁻ by N₂H₄. It is found that the bandgap structure of CdIn₂S_4‐xSe_x nanocrystals can be adjusted from 2.42 to 1.87 eV by varying the molar ratio of Se/S. Compared with pure CdIn₂S₄, the CdIn₂S_4‐xSe_x solid‐solution photocatalyst clearly represents excellent photocatalytic hydrogen production performance, while the CdIn₂S_4‐xSe_x (x = 0.4) solid‐solution nanocrystal exhibits the optimal hydrogen‐production efficiency of 314.24 µmol h⁻¹, which is 3.3 times superior to that of CdIn₂S₄ (94.83 µmol h⁻¹). It is found that the introduction of Se increases the charge density of S²⁻ to form electron‐enriched S^{(2+δ )−}, which can promote the effective adsorption of H⁺ for the following interfacial hydrogen‐evolution reaction. Meanwhile, the CdIn₂S_4‐xSe_x solid‐solution nanocrystals have a higher conduction band and stronger visible‐light absorption ability, which is also essential for accelerating photocatalytic hydrogen‐production efficiency. This study may offer possibilities for developing high‐performance photocatalysts.