Atomic Heterointerface Engineering and Non‐Equilibrium Carrier Dynamics for Enhanced Photocatalysis in Halide Perovskite/MoS2 Systems

Solar‐driven photocatalysis holds promise for fuel production, with halide perovskites leading owing to superior light absorption and carrier diffusion. However, precise control and understanding of interfacial charge separation dynamics in their heterostructures remain challenging. Using formamidinium lead bromide/molybdenum disulfide (FAPbBr3/MoS2) as a model, we engineered Pb‐rich, Pb‐neutral, and Pb‐deficient surfaces via precursor stoichiometry tuning, modulating interface coupling through Pb‐S bonds. High‐density atomic bridging in Pb‐rich interfaces boosts photogenerated charge separation efficiency from 29% to 63%, yielding a 98‐fold hydrogen production increase and record 8.69% solar‐to‐hydrogen efficiency. Theoretical and experimental results demonstrate that the long carrier diffusion length and high photogenerated charge density of perovskites create a steep charge density gradient at the interface. This gradient directly induces a non‐equilibrium internal electric field, which governs the charge transport dynamics. This work demonstrates the feasibility of sophisticated heterointerface tailoring and advances the understanding of the driving forces behind interfacial charge separation for perovskite photocatalysts.