Fluorination over Cr doped layered perovskite Sr2TiO4 for efficient photocatalytic hydrogen production under visible light illumination

Cr doped Ruddlesden-Popper compound Sr2TiO4 has been successfully modified by fluorine to form a new compound Sr2Ti0.95Cr0.05O3F2. Structure analysis suggests two types of fluorine in the structure of this new compound, i.e. intralayer and interlayer F, which induce strong built-in electric field within this layered compound. The electric field stems from uneven distribution of F atoms on the two sides of perovskite layers therefore leads to charge disproportionation. DFT calculations suggest that this unique structural feature is highly beneficial for charge dissociations as it breaks the coplanar settlement of conduction band minimum and valence band maximum whilst maintains the 2D charge transportation properties. This is clearly demonstrated by the superior photocatalytic activities of Sr2Ti0.95Cr0.05O3F2 for hydrogen production from water. Apparent quantum efficiency (AQE) as high as 1.16% at 420 ± 20 nm has been achieved which stands as the highest AQE reported on Sr2TiO4 to date. Photoelectrochemical (PEC) analysis confirms improved charge separation conditions and prolonged charge lifetime.