Synergistic Interactions of Bulk Polarization and Built‐In Electric Field Inducing 2D/2D S‐Scheme Homojunction Toward Enhanced Photocatalytic Performance

The rational design of S-scheme photocatalysts, achieved by serially integrating two different semiconductors, represents a promising strategy for efficient charge separation and amplified photocatalytic performance, yet it remains a challenge. Herein, ZnIn₂S₄ (ZIS) and oxygen-doped ZnIn₂S₄ (O-ZIS) nanosheets are chosen to construct a homojunction catalyst architecture. Theoretical simulations alongside comprehensive in situ and ex situ characterizations confirm that ZIS and O-ZIS with noncentrosymmetric layered structures can generate a polarization-induced bulk-internal electric field (IEF) within the crystal. A robust interface-IEF is also created by the strong interfacial interaction between O-ZIS and ZIS with different work functions. Owing to these features, the O-ZIS/ZIS homojunction adopts an S-scheme directional charge transfer route, wherein photoexcited electrons in ZIS and holes in O-ZIS concurrently migrate to their interface and subsequently recombine. This enables spatial charge separation and provides a high driving force for both reduction and oxidation reactions simultaneously. Consequently, such photocatalyst exhibits an H₂ evolution rate up to 142.9 µmol h^-1 without any cocatalysts, which is 4.6- and 3.4-fold higher than that of pristine ZIS and O-ZIS, respectively. Benzaldehyde is also produced as a value-added oxidation product with a rate of 146.9 µmol h^-1. This work offers a new perspective on the design of S-scheme systems.