Bandgap engineering of lead-free double perovskites for efficient photocatalysis

Lead-free halide perovskites represent promising candidates in optoelectronics due to their excellent properties, such as high stability, mobility, defect tolerance and low-cost processes. However, their applications in photovoltaic and photocatalysis are limited by their wide bandgap nature. Here, we introduced Sb³⁺ and Sb⁵⁺ ions into the double perovskite Cs₂AgBiCl₆, successfully narrowing its bandgap and extending the absorption band edge to 1450 nm, representing the broadest near-infrared (NIR) response reported for lead-free perovskites. Remarkably, the Sb-doped perovskite catalyst exhibits a significantly enhanced photocatalytic hydrogen generation rate. Specifically, Cs₂AgBiCl₆:0.63% Sb⁵⁺ achieves a hydrogen generation rate of 4835.9 μmol g^-1 h^-1 under 420-780 nm irradiation, which is an order of magnitude improvement over that of pure Cs₂AgBiCl₆. This material maintains high photocatalytic performance within the NIR range and demonstrates sustained stability over a 16-hour continuous reaction. This study sets the stage for fabricating stable perovskite-based photocatalysts and breaks through the spectral absorption range of halide perovskite materials, and the proposed strategy extends light absorption to activate NIR photoactivity.