Metal Halide Perovskite Heterojunction for Photocatalytic Hydrogen Generation: Progress and Future Opportunities

Abstract Photocatalytic hydrogen generation paves a promising way to mitigate the global energy crisis and deteriorative environmental issues. Among different materials, metal halide perovskites (MHPs) have recently emerged as a promising class of inexpensive and easy‐to‐make semiconductors for various photocatalytic applications such as organic contaminant degradation, CO 2 reduction, H 2 evolution, and N 2 fixation. Although MHPs‐based standalone photocatalysts offer architectural simplicity, they provide restricted control over recombination processes and spatial separation of redox half‐reactions. Meanwhile, heterojunction systems are of growing interest due to their ability to control energy‐consuming redox processes and effectively suppress charge carrier recombination. In this review, the authors elaborately discuss perovskite‐based heterojunction photocatalysts for hydrogen generation both from a material chemistry point of view and band alignment perspective. They discuss the design principle of MHP heterostructures necessary for H 2 evolution and the underlying photo‐physics behind process optimization. Moving forward, they conclude by meticulously outlining the ongoing challenges, opportunities, and future outlooks for MHP‐based heterojunction photocatalysts for H 2 evolution.