Metal halide perovskite nanostructures and quantum dots for photocatalytic CO2 reduction: prospects and challenges

Photocatalytic CO2 reduction is a promising technology for production of solar fuels to address global environmental concerns. Metal halide perovskite (MHP) nanocrystals and quantum dots possess excellent features like high surface-to-volume ratio, broad visible-light absorption range, tunable bandgap, and high defect tolerance, making them ideal candidates for photocatalytic applications. Since the initial studies in 2017, numerous efforts have been devoted to boost the performance of MHP nanocrystals for photocatalytic CO2 conversion. In this review, we briefly state the fundamentals, basic properties, and recent progress in the use of MHP nanocrystals for photocatalytic CO2 reduction. Structural modifications of MHP nanocrystals are then summarized for enhanced photocatalytic performance, and they can be roughly divided into two directions: direct modulation of the pristine nanocrystals and construction of heterostructure composites. Subsequently, we lay particular emphasis on the issues obstructing MHP nanocrystals based photocatalysis from practical application, specifically, reaction systems/platforms and the toxicity of lead (Pb). The latest groundbreaking progress including the development of novel photocatalytic system/platform and the construction of lead-free MHP nanocrystal photocatalysts are then discussed. Finally, we highlight the outlook of the MHP nanocrystals towards photocatalytic CO2 reduction.