Perovskite CsCuClxBr3‐ x Microcrystals: Band Structure, Photochemical Stability, and Photocatalytic Properties

Although Pb‐based metal halide perovskites (MHPs) have excellent photoelectric characteristics, their toxicity remains a limiting factor for their widespread application. In the paper, a series of CsCuClxBr3‐x (x = 1, 2, 3) MHP microcrystals were developed and their hydrogen evolution performance in ethanol and HX (X = Cl, Br) was also studied. Among them, CsCuCl3 microcrystals exhibit high hydrogen evolution performance in both HX and ethanol, attributed to their longest average lifetime and suitable band structure. Additionally, the effect of different sacrificial agents on photocatalytic hydrogen production indicates that the photogenerated hole (h+) plays a critical role. MHPs can maintain a dynamic equilibrium of dissolution and precipitation in HX‐saturated aqueous solutions, thereby overcoming the stability issues associated with perovskite. The phase transition of CsCuClxBr3‐x during photocatalysis is monitored by the XRD technique. CsCuCl3 shows high stability in saturated HCl aqueous solution, and excellent photocatalytic performance with a hydrogen production rate of CsCuCl3 microcrystals reached 103.98 μmol g‐1 at 210 min. Our study expands the development prospects of CsCuCl3 in the field of photocatalytic solar fuel generation.