Efficient Photocatalytic Hydrogen Evolution Enabled by Defect‐ and Interface‐Induced Dual Built‐in Electric Fields in a ZnIn 2 S 4 /1T‐2H WS 2 Heterojunction

ABSTRACT Efficient photocatalysis requires coordinated regulation of charge transport across both bulk and interfacial regions. Here, we introduce an in situ hydrothermal‐solvothermal method that simultaneously creates a defect‐induced p‐n homojunction in ZnIn 2 S 4 (ZIS) and a type‐II heterojunction with hybrid 1T‐2H WS 2 , forming antiparallel internal‐interfacial built‐in electric fields (BIEF) that are confirmed by spectroscopic, electronic, optical, and theoretical analyses. Under the guidance of this dual‐field coupling effect, photoexcited carriers undergo more efficient separation, enabling the effective modulation of bulk carrier migration and directing electrons toward sulfur‐vacancy (S v ) sites in ZIS for efficient hydrogen evolution. The hybrid 1T‐2H phases of WS 2 further enhance light absorption and facilitate rapid charge generation and transfer, reinforcing the dual‐BIEF‐driven transport pathway. The optimized ZIS/WS 2 photocatalyst achieves a hydrogen evolution rate of 44.97 mmol g −1 h −1 and an apparent quantum efficiency of 24.54% at 400 nm. This work establishes antiparallel dual‐BIEF engineering combined with 1T‐2H hybrid‐phase modulation as a platform for directional charge‐dynamic control, offering a pathway toward efficient solar‐to‐hydrogen conversion.