Highly Efficient Noble‐Metal Free Photocatalytic Hydrogen Generation Using Water‐Stable 4,4′‐Vinylenedipyridine‐Based Halide Perovskites

Low‐dimensional perovskites show great promise due to their stronger structural stability against external stressors, in particular, moisture. However, the alternance of organic and inorganic layers contributes to form a quantum‐well structure leading to the bi‐dimensional confinement of the carrier's transport, thus limiting the performances in solar‐to‐fuel conversion applications. To overcome this issue, the synthesis of the 1D vinylenedipyridine‐based (4,4′‐VDP)Pb 2 X 6 perovskite (X = Br, I), whose specificity is to combine pi‐conjugated spacer and cation–pi interactions, is reported. The pi‐conjugation electronically connects the inorganic layers, and the cation–pi interactions facilitate stability against water. As a result, exceptional structural and photostability in a large range of aqueous pH is demonstrated. Whereas (4,4′‐VDP)Pb 2 Br 6 does not show photocatalytic activity toward hydrogen production due to misaligned band energy position with HBr, the iodide counterpart (4,4′‐VDP)Pb 2 I 6 perovskite produces a substantial amount of hydrogen (1.81 mmol g −1 after 24 h of photoreaction), without noble metal catalyst utilization and under standard AM 1.5 G illumination conditions.