Unlocking Interfacial Interactions of In Situ Grown Multidimensional Bismuth-Based Perovskite Heterostructures for Photocatalytic Hydrogen Evolution

To combat the energy crisis and environmental pollution, developing renewable energy technology such as hydrogen (H₂) production is necessary. The sulfur–iodine thermochemical cycle has high commercial potential in conducting hydrogen iodide (HI) splitting for H₂ generation, but it requires high-temperature conditions. In comparison, photocatalytic HI splitting of halide perovskites is non-polluted and low-cost for H₂ production at room temperature. Herein, an in situ constructed multidimensional bismuth (Bi)-based 3D/2D EDABiI₅/MA₃Bi₂I₉ perovskite heterojunction is developed first by synergistically integrating dimensionality control with heterostructure engineering. Accordingly, the optimal EDABiI₅/MA₃Bi₂I₉ without any co-catalysts exhibits the H₂ evolution rate of 213.63 µmol h⁻¹g⁻¹ under irradiation. Equally importantly, interfacial dynamics of solid/solid and solid/liquid interfaces play a crucial role in photocatalytic performance. Therefore, using temperature-dependent transient photoluminescence and electrochemical voltammetric techniques, it is confirmed that the exciton transportation of EDABiI₅/MA₃Bi₂I₉ is accelerated by stronger electronic coupling arising from an enhanced overlap of electronic wavefunctions. Moreover, the effective diffusion coefficient and electron transfer rate of EDABiI₅/MA₃Bi₂I₉ demonstrate efficient heterogeneous electron transfer, resulting in improved photocatalytic hydrogen production. Consequently, the in situ formation of perovskite heterostructures studied by a combination of photophysical and electrochemical techniques provides new insights into green hydrogen evolution and interfacial interaction dynamics for commercial applications of solar-to-fuel technology.