Stability Engineering of Perovskite Photoelectrodes for PEC Water Splitting

ABSTRACT Solar‐driven photoelectrochemical (PEC) water splitting offers a direct route to green hydrogen. Halide perovskites, with strong light absorption, tunable band structure, and low‐temperature processability, are attractive for PEC applications, but operation in aqueous environments remains challenging. Intrinsic and external degradation, including phase instability, ion migration, dissolution, interfacial side reactions, and photocorrosion, undermine durability, suppress solar‐to‐hydrogen (STH) efficiency, and hinder large‐area deployment. This Review summarizes key bottlenecks governing perovskite photoelectrodes and discusses two complementary routes: intrinsic stabilization through compositional and defect engineering and external protection through encapsulation architectures that block electrolyte ingress while preserving charge transport and stable catalyst integration. We further review metal‐based encapsulation, carbon‐based conductive barriers, and conductive adhesive–barrier interface, and then summarize recent advances in perovskite photoanodes, photocathodes, and integrated PEC systems under realistic operating conditions. We also consider pathways toward module‐scale deployment, and outline future priorities in environmentally responsible design, standardized evaluation, and data‐driven optimization to advance durable and scalable perovskite PEC hydrogen production.