Bandgap Funneling in Bismuth‐Based Hybrid Perovskite Photocatalyst with Efficient Visible‐Light‐Driven Hydrogen Evolution

Abstract The photocatalytic system using hydrohalic acid (HX) for hydrogen production is a promising strategy to generate clean and renewable fuels as well as value‐added chemicals (such as X 2 /X 3 − ). However, it is still challenging to develop a visible‐light active and strong‐acid resistive photocatalyst. Hybrid perovskites have been recognized as a potential photocatalyst for photovoltaic HX splitting. Herein, a novel environmentally friendly mixed halide perovskite MA 3 Bi 2 Cl 9–x I x with a bandgap funnel structure is developed, i.e., confirmed by energy dispersive X‐ray analysis and density functional theory calculations. Due to gradient neutral formation energy within iodine‐doped MA 3 Bi 2 Cl 9 , the concentration of iodide element decreases from the surface to the interior across the MA 3 Bi 2 Cl 9–x I x perovskite. Because of the aligned energy levels of iodide/chloride‐mixed MA 3 Bi 2 Cl 9–x I x , a graded bandgap funnel structure is therefore formed, leading to the promotion of photoinduced charge transfer from the interior to the surface for efficient photocatalytic redox reaction. As a result, the hydrogen generation rate of the optimized MA 3 Bi 2 Cl 9–x I x is enhanced up to ≈341 ± 61.7 µmol h −1 with a Pt co‐catalyst under visible light irradiation.