A versatile approach for the immobilization of lead-free Cs₃Bi₂I₉ perovskites for photocatalytic CO₂ reduction

Abstract

This work proposes a novel approach to immobilize the lead-free bismuth halide perovskite Cs3Bi2I9 in mica and cellular porous concrete supports. The perovskites were evaluated as visible-light active photocatalysts in the CO2 reduction to generate HCOOH with high energy conversion efficiencies. The approach ensured the material’s stability exposed to an aqueous medium under visible light irradiation. According to the results, the Cs3Bi2I9 particles exhibited a different morphology depending on the support used; its growth on mica favored the formation of well-defined hexagonal particles. Meanwhile, the porous concrete favored the formation of needle-like particles. Also, the optical characterization indicated that when the Cs3Bi2I9 particles grew as a thin film, their surface energy seemed higher, favoring the formation of layered structures related to the lattice defects. On the other hand, the concrete cellular offers a porous interconnected network, an excellent medium to encapsulate the Cs3Bi2I9 particles. These properties favored the formation of 2,570 µmol of HCOOH in the steady state with an energy conversion efficiency of up to 24.3%, which is higher than the required value to scale up the process. The analysis of the perovskite after the reaction revealed that the sample maintains its properties, and it shows the growth of flake-like particles on top of hexagonal particles, which eventually participate in the photocatalytic reaction. Also, it was demonstrated that the approach implemented here favored high thermal stability of the Cs3Bi2I9 perovskite.