Bismuth-Based Perovskite Heterostructures: In Situ Formation of Bismuth-Based Perovskite Heterostructures for High-Performance Cocatalyst-Free Photocatalytic Hydrogen Evolution (Adv. Funct. Keywords: co-catalyst-free; in situ formation; perovskite heterojunctions; photocatalytic hydrogen evolution EN co-catalyst-free in situ formation perovskite heterojunctions photocatalytic hydrogen evolution 1 1 1 12/24/20 20201222 NES 201222 In article number 2006919, Hsien-Yi Hsu and co-workers report a feasible solvent-engineering technique for in-situ formation of a lead-free bismuth (Bi)-based perovskite heterostructure for high-performance co-catalyst-free photocatalytic hydrogen generation. Driven by energy band alignment across the interface of a phase junction, the air-stable MA SB 3 sb Bi SB 2 sb I SB 9 sb /DMA SB 3 sb BiI SB 6 sb perovskite heterostructure exhibits enhanced photoinduced charge separation, resulting in outstanding visible-light-induced photocatalytic activity for H SB 2 sb evolution in aqueous hydrogen iodide solution. [Extracted from the article]