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

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 X2 /X3- ). 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 MA3 Bi2 Cl9-x Ix 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 MA3 Bi2 Cl9 , the concentration of iodide element decreases from the surface to the interior across the MA3 Bi2 Cl9-x Ix perovskite. Because of the aligned energy levels of iodide/chloride-mixed MA3 Bi2 Cl9-x Ix , 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 MA3 Bi2 Cl9-x Ix is enhanced up to ≈341 ± 61.7 µmol h-1 with a Pt co-catalyst under visible light irradiation.