Tuning morphology via simple routes: Advancing lead-free perovskites for CO2 photoreduction.

Photocatalytic carbon dioxide (CO2) reduction offers a promising approach by harnessing solar energy to transform CO2 into value-added fuels and chemicals. Among various photocatalysts, halide perovskite-based materials, specifically lead-based, have attracted significant attention for CO2 reduction. However, developing lead-free alternatives is crucial to mitigate concerns related to environmental toxicity. Herein, lead-free, morphology-controlled Cs3Bi2Br9 (CBB) photocatalysts were synthesized via a simple antisolvent reprecipitation method under ambient conditions. Size reduction increased the number of active sites for CO2 adsorption and suppressed charge recombination, enhancing photocatalytic performance. Building on this, the formation of a hollow structure improved light-harvesting efficiency, shortened charge transport pathways, and further enhanced CO2 adsorption, collectively leading to a significant boost in CO2 reduction activity. In addition, computational studies revealed that the presence of vacancies, induced by hollow formation, had significant effects on the electronic redistribution of charges as well as CO2 adsorption and activation capabilities. The combined benefits led to a 2.5-fold increase in methane (CH4) production for the optimized, size-reduced, hollow CBB sample (CBB-MH). This study reports a simple modification for structural engineering, effectively enhancing CBB as an independent material for efficient CO2 reduction.