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. A 2D/2D S‐scheme homojunction is designed by interfacing oxygen‐doped ZnIn2S4 (O‐ZIS) and pristine ZIS nanosheets. The B‐IEF within ZIS (O‐ZIS) and I‐IEF at the junction facilitate a direct S‐scheme charge transfer pathway, enabling spatial charge separation and providing robust redox capabilities. These features endow the homojunction with remarkable photocatalytic H2 evolution coupled with selective benzyl alcohol oxidation without any cocatalysts.