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.