The utilization of perovskites as photocatalysts to convert CO₂ into fuels and chemicals has received wide attention recently. However, their instability in water hinders their long-term application for overall photocatalytic CO₂ reduction. Herein, we integrate the water-stable perovskite-like organolead iodide crystalline material [Pb₈I₈(H₂O)₃]⁸⁺[^–O₂C(CH₂)₄CO₂^–]₄ (TJU-16) with Au co-catalyst for photocatalytic CO₂ reduction in aqueous solution without sacrificial reagent. Under the AM 1.5 G simulated illumination, the TJU-16 with 0.19 wt.‰ Au co-catalyst steadily generated electrons for CO₂ reduction reaction, which was 2.2 times of pure TJU-16. The Au_0.19/TJU-16 catalyzed CO₂ reduction at a rate of 84.2 μmol·g⁻¹·h⁻¹, and achieved a solar-to-fuel (STF) conversion efficiency of 0.034%. Our work will motivate the rational design of water-stable perovskite-like materials for photocatalytic applications.

Cesium lead iodide (CsPbI₃) is a promising photo-absorber for perovskite photovoltaics due to its high thermal stability and relatively small bandgap. However, there are many defects in solution processed polycrystalline CsPbI₃ films especially at the grain boundaries (GBs), which limit the power conversion efficiency (PCE) of CsPbI₃ solar cells. In this work, we introduced CsPbBr₃ quantum dots (QDs) on top of the CsPbI₃ film to passivate the defects. As CsPbBr₃ QDs have a small size and a similar crystal structure as the CsPbI₃, they are excellent modifiers to fill in the GBs and heal the defects. Moreover, we find there is an anion exchange reaction between the CsPbBr₃ QDs and CsPbI₃ films, which is evidenced by photoluminescence spectra and grazing incidence X-ray diffraction patterns. The QDs treated films show enhanced carrier lifetime and reduced defect density. Additionally, the ligands on CsPbBr₃ QDs increase the hydrophobicity of the films. As a result, the QDs treated CsPbI₃ solar cells prepared at high temperature obtain PCEs exceeding 16% with high stability.