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 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.