Water-resistant perovskite-inspired copper/silver pnictohalide nanocrystals for photoelectrochemical water splitting

Lead halide perovskites (LHPs) photoelectrodes for photoelectrochemical (PEC) water splitting are promising candidates for solar-to-fuel conversion. However, the poor stability of LHPs in aqueous electrolyte media, together with the toxicity of lead, restricts the practical application of LHP photoelectrodes. Herein, we report the first-ever colloidal synthesis of quaternary Cu1.4Ag0.6BiI5 nanocrystals (NCs), a new lead-free perovskiteinspired nanomaterial, by a facile hot injection method. The Cu1.4Ag0.6BiI5 NCs exhibit an extraordinary water resistance, due to the well-defined coverage of hydrophobic ligands on the surface of NCs with unique layered cation disordered structure. Together with their high structural stability, the Cu1.4Ag0.6BiI5 NCs-based photoanode displays a maximum photocurrent density of 4.62 mA cm-2 at 1.23 V vs. reversible hydrogen electrode, and an applied bias photo-to-current efficiency of 2.94% without any protective layer. Our study highlights the great potential of lead-free Cu1.4Ag0.6BiI5 NCs-based photoelectrodes for a wide range of low-cost, eco-friendly, and high-performance PEC applications.