Interface-Electrolyte Gating of Defect-Selective Recombination Tunes Charge-Carrier Dynamics and Photoelectrochemical...

Defect-mediated recombination in oxide photoelectrodes is widely treated as an intrinsic loss pathway, yet its selective control remains largely unexplored. Here, we demonstrate that oxygen-vacancy-mediated recombination in ZnO can be effectively modulated through interface engineering and electrolyte-dependent kinetics. In BiVO₄/ZnO, interfacial coupling promotes recombination via specific defect states, whereas incorporation of Bi₂S₃ suppresses this pathway and shifts the system toward more efficient charge separation. In the presence of sulfide, the ternary Bi₂S₃/BiVO₄/ZnO photoanode exhibits the highest photocurrent, applied bias photon to current efficiency (ABPE), and incident photon to current efficiency (IPCE), accompanied by a transition in the intensity modulated photocurrent spectroscopy (IMPS) response toward a single dominant charge-transfer time constant. Combined photoluminescence, photoelectron spectroscopy, surface photovoltage, and photoelectrochemical analyses indicate that buried interfaces act as electronic gates, while fast sulfide oxidation provides complementary chemical gating, together redistributing defect-mediated recombination pathways through selective modulation of defect-state activity. These findings demonstrate that defect-selective recombination can be controlled to enhance photoelectrochemical performance and identify interface-electrolyte gating as an effective strategy for solar-driven hydrogen generation from sulfide-containing waste streams.