Cs3Bi2Br9/Bi19Br3S27 Z-scheme heterojunction for visible-to-near-infrared light-driven photocatalytic CO2 reduction

The urgent need for clean energy has driven extensive research into efficient photocatalytic systems for CO 2 reduction. Lead-free Cs 3 Bi 2 Br 9 perovskites are particularly promising in this context, yet the photocatalytic performance of single-component Cs 3 Bi 2 Br 9 is often hindered by its narrow absorption in visible-light range. Here, we present a visible-to-near-infrared (vis-to-NIR) responsive Cs 3 Bi 2 Br 9 /Bi 19 Br 3 S 27 Z -scheme heterojunction photocatalyst, achieved by creating a high-quality interface upon in-situ growth. This heterojunction design markedly boosts CO₂-to-methane conversion, achieving electron consumption rates that are 70 and 124 times higher than those of pristine Cs 3 Bi 2 Br 9 and Bi 19 Br 3 S 27 , respectively. Mechanistic studies indicate that the formation of a strong built-in electric field at the interface facilitates efficient charge separation and transfer, significantly boosting photocatalytic performance. Notably, the photocatalytic performance of Cs 3 Bi 2 Br 9 /Bi 19 Br 3 S 27 heterojunction surpasses that of most lead-free halide perovskite photocatalysts. Our findings offer a new paradigm for interface engineering in photocatalysis and advance the development of vis-to-NIR responsive perovskites for sustainable energy conversion.