Bypassing Schottky constraints via defect-mediated hydrogen transfer in hydrodechlorination.

Hydrogen-mediated transformations at heterointerfaces are often limited by a fundamental kinetic mismatch: the need for strong interfacial polarization to stabilize active hydrogen (H*) often creates high Schottky barriers that impede the necessary electron supply. Here, using a defect-engineered MoS2/Fe(OH)2 heterojunction for chloroform (CF) hydrodechlorination, we resolve this trade-off by engineering a defect-band hybridization mechanism. We observe that while increasing sulfur-vacancy density in MoS2 upshifts its conduction-band minimum-nominally raising the barrier for electron injection-it paradoxically enhances interfacial electron transport. Electronic structure analysis reveals that interfacial electric-field coupling drives strong hybridization between vacancy-derived states and the MoS2 conduction band. This forms quasi-continuous, defect-assisted tunneling channels that allow electrons to bypass the energetic barrier. The resulting electronic reconstruction stabilizes interfacial H* in a reactive yet mobile state, shifting the reaction regime from an Fe(II)-dominated single-electron transfer to a precise H*-mediated hydrogen atom transfer pathway. This mechanism suppresses hydrogen evolution and enables highly selective deep hydrodechlorination, providing a generalizable blueprint for manipulating electron-proton coupling at mismatched heterointerfaces.