Lead‐Free Bismuth‐Based Halide Perovskites with Excellent Stability for Visible‐light‐Driven Photoelectrochemical Water Splitting

Abstract Lead‐free halide perovskites have been developed as an alternative to lead‐based perovskite materials. Bi‐based halide perovskites Cs 2 AgBiCl 6 and Cs 3 Bi 2 Cl 9 are synthesized through the hydrothermal method and investigated their photoelectrochemical properties toward water splitting. The formation of the halide perovskites is confirmed by XRD, Raman spectroscopy, SEM, EDAX and XPS techniques. Optical properties are measured by UV‐Vis spectroscopy and Mott‐Schottky plots confirmed that both the materials are p‐type semiconductors with a bandgap of 2.72 eV and 3.05 eV for Cs 2 AgBiCl 6 and Cs 3 Bi 2 Cl 9 respectively. The photocurrent density of water oxidation on Cs 2 AgBiCl 6 and Cs 3 Bi 2 Cl 9 are 10 μA/cm 2 and 6 μA/cm 2 at 0.9 V (vs Ag/AgCl) respectively and both are highly stable over 300 sec under chopped condition and also the photoelectrocatalyst stable over 10 h during the chronoamperometry studies. The experimental data shows that the photoelectrochemical water splitting activity of Cs 2 AgBiCl 6 is better than Cs 3 Bi 2 Cl 9 . This work suggests these materials will be a potential candidate for green hydrogen and oxygen production using solar energy.