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

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 ZnIn₂S₄ (ZIS) and a type-II heterojunction with hybrid 1T-2H WS₂, 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 (Sv) sites in ZIS for efficient hydrogen evolution. The hybrid 1T-2H phases of WS₂ further enhance light absorption and facilitate rapid charge generation and transfer, reinforcing the dual-BIEF-driven transport pathway. The optimized ZIS/WS₂ photocatalyst achieves a hydrogen evolution rate of 44.97 mmol g⁻¹h⁻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.