Enhancing the Photocatalytic Hydrogen Evolution Activity of Mixed-Halide Perovskite CH3NH3PbBr3–xIx Achieved by Bandgap Funneling of Charge Carriers

Powder samples of mixed halide perovskite MAPbBr3–xIx (MA = methylammonium ion, CH3NH3+) were prepared by employing a facile light-assisted halide-exchange method in aqueous halide solution at room temperature. It is found that the distribution of iodide ions in the MAPbBr3–xIx particles tends to be largest on the surface and becomes lower on going into the interior so that they have a correct bandgap funnel structure that is needed for transferring photogenerated charge carriers from the interior to the surface. Consequently, the MAPbBr3–xIx/Pt powder sample (250 mg) exhibits an enhanced photocatalytic activity for a H2 evolution under visible light (100 mW cm–2, λ ≥ 420 nm) with the rate of 651.2 μmol h–1 and a solar-to-chemical conversion efficiency of 1.05%.