Activating photocatalytic hydrogen generation on inorganic lead-free Cs2AgBiBr6 perovskite via reversible Cu2+/Cu+ redox couple

Photocatalytic hydrogen evolution from hydrohalic acid by lead-free metal halide perovskite holds great potential but still faces ineffective charge separation and low solar-to-hydrogen conversion efficiency challenges. In the present study, a reversible Cu2+/Cu+ redox couple is introduced into the inorganic lead-free perovskite Cs2AgBiBr6/(HBr + H3PO2)-based photocatalytic H2 evolution system to achieve fast hole extraction and effective charge separation. The rapid Cu+ oxidation by photogenerated holes with more favorable thermodynamics and faster kinetics overcomes the intrinsic slow Br− oxidation half-reaction, leading to rapid extraction and consumption of holes, which dramatically alleviates the charge recombination and improves the utilization efficiency of electrons for protons reduction. As a result, up to 70 times enhancement of H2 production is achieved on Cs2AgBiBr6 photocatalyst with the introduction of Cu2+/Cu+ redox couple.