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<inf>2</inf>X<inf>6</inf> 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<inf>2</inf>Br<inf>6</inf> does not show photocatalytic activity toward hydrogen production due to misaligned band energy position with HBr, the iodide counterpart (4,4′-VDP)Pb<inf>2</inf>I<inf>6</inf> 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.