Boosting the internal electron transfer of two-dimensional hybrid perovskites via fluorination of organic cation towards enhanced photocatalytic hydrogen production

Two-dimensional (2D) organic-inorganic hybrid perovskites have emerged as promising candidates for photocatalytic hydrogen production due to their unique optoelectronic properties. However, the organic cations in the interlayer of 2D perovskites generally retard the internal charge transfer due to the large interlayer van der Waals barrier for electron transfer, which defines the imperative to engineering the organic entity. Herein, taking phenethylammonium lead iodide (PEA2PbI4) as a typical example, we show that by substituting the hydrogen with fluorine atom in the para-position of the phenyl group, the internal electron transfer was promoted remarkably. The improved electron transfer is ascribed to the introduction of fluorine with strong electronegativity, which leads to interlayer polarization and almost zero-potential barrier between the organic layers. Consequently, 4-FPEA2PbI4 exhibits ca. 8.2 times higher photocatalytic H2 evolution activity than PEA2PbI4. This work establishes a paradigm for optimizing the photocatalytic properties of 2D hybrid perovskites by engineering the organic cations.