Inspired by natural photosynthesis, the photocatalytic CO₂ reduction reaction (CO2RR) stands as a viable strategy for the production of solar fuels to mitigate the high dependence on highly polluting fossil fuels, as well as to decrease the CO₂ concentration in the atmosphere. The design of photocatalytic materials is crucial to ensure high efficiency of the CO2RR process. So far, perovskite materials have shown high efficiency and selectivity in CO2RR to generate different solar fuels. Particularly, bismuth halide perovskites have gained much attention due to their higher absorption coefficients, their more efficient charge transfer (compared to oxide perovskites), and their required thermodynamic potential for CO2RR. Moreover, these materials represent a promising alternative to the highly polluting lead halide perovskites. However, despite all the remarkable advantages of bismuth halide perovskites, their use has been limited, owing to instability concerns. As a consequence, recent reports have offered solutions to obtain structures highly stable against oxygen, water, and light, promoting the formation of solar fuels with promising efficiency for CO2RR. Thus, this review analyzes the current state of the art in this field, particularly studies about stability strategies from intrinsic and extrinsic standpoints. Lastly, we discuss the challenges and opportunities in designing stable bismuth halide perovskites, which open new opportunities for scaling up the CO2RR.

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.