The separation of photo-generated carriers in heterojunctions plays a crucial role in regulating the built-in electric field. The design of materials with directional migration characteristics inside the bulk phase and at the interface between the two phases is of great significance for studying photocatalytic hydrogen evolution. The P-CdS/Ag 2 S composite photocatalytic system prepared in this study was doped with P element by heating CdS and NaH 2 PO 2 in a muffle furnace, resulting in the directed migration of photo-generated charges in the prepared sample driven by an internal electric field. By in-situ deposition of Ag 2 S on the surface of P-CdS, a Janus heterojunction was prepared to enhance the transfer of charge carriers at the phase interface. The hydrogen evolution rate of P-CdS/Ag 2 S is 12.44 mmol·h −1 ·g −1 , which is 30 times higher than that of the previously prepared pure CdS sample (0.411 mmol·h −1 ·g −1 ). This significant improvement in photocatalytic performance is attributed to the doping of P element and the in-situ loading of Ag 2 S co-catalyst, which together promote the effective separation and transport of photogenerated charge carriers, thereby enhancing the photocatalytic activity of the material. This work is of great significance for exploring the charge-directed transfer problem of sulfide photocatalysts in the field of photocatalytic hydrogen evolution. Graphical
Cr doped Ruddlesden-Popper compound Sr 2 TiO 4 has been successfully modified by fluorine to form a new compound Sr 2 Ti 0.95 Cr 0.05 O 3 F 2 . 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 Sr 2 Ti 0.95 Cr 0.05 O 3 F 2 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 Sr 2 TiO 4 to date. Photoelectrochemical (PEC) analysis confirms improved charge separation conditions and prolonged charge lifetime.
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