Multi‐Hydrogen Adsorption as a Dynamic Electronic Gate for Ultrafast Interfacial Charge Transfer

Reactive materials operate under dynamically evolving adsorption environments, yet how cooperative adsorbates reshape interfacial electronic structure and charge‐transfer kinetics remains poorly understood. Here we show that multi‐hydrogen adsorption can function as a dynamic electronic gate that reprograms interfacial charge‐transfer energetics. Using a sulfur‐rich amorphous CoReS 2+x cocatalyst as a model system, we demonstrate that abundant unsaturated sulfur sites enable cooperative multi‐hydrogen adsorption, which induces spontaneous electron delocalization and generates an electron‐deficient interfacial state. This adsorption‐driven electronic redistribution reverses the thermodynamic directionality of electron injection from CdZnS, converting an originally endothermic process into a spontaneous one. Femtosecond transient absorption spectroscopy further reveals that the gated interface accelerates interfacial electron transfer to the ultrafast regime, in agreement with first‐principles calculations. The resulting a‐CoReS 2+x /CdZnS system achieves highly efficient photocatalytic hydrogen evolution from biomass‐derived formic acid with an apparent quantum efficiency of 67.8%. More broadly, these findings establish multi‐adsorbate‐induced electronic gating as a general mechanism for dynamically programming interfacial charge transfer in catalytic and energy‐conversion materials operating under realistic reactive environments.