Unraveling Electron Transfer Dynamics in (Co-Mo)S Heterostructures for Sustainable Hydrogen Evolution.

Scalable synthesis of efficient electrocatalysts with sustained activity remains a major challenge for practical water splitting. Herein, we report a confined mechanochemical strategy for the ultrafast and scalable synthesis of mesoporous (Co-Mo)S heterostructures with abundant interfacial sites. The optimized catalyst exhibits excellent bifunctional performance, delivering overpotentials of 150 mV (HER) and 311 mV (OER) with low Tafel slopes (74 mV dec-1) and minimal charge-transfer resistance (3.8 Ω). High Faradaic efficiencies (96% for HER and 98% for the OER) confirm efficient charge utilization. Kinetic analyses reveal accelerated electron-transfer dynamics, supported by in situ electrochemical impedance spectroscopy (EIS) and reduced activation energy derived from Arrhenius studies, while trumpet plot analysis indicates enhanced rate constants across varying pH. The catalyst also demonstrates promising oxygen reduction reaction (ORR) activity and robust durability. Notably, an alkaline electrolyzer assembled with (Co-Mo)S requires only 1.58 V to achieve 10 mA cm-2, highlighting its practical potential. This work demonstrates that interfacial engineering in (Co-Mo)S heterostructures enables efficient charge transfer and improved catalytic kinetics, offering a scalable pathway for advanced electrocatalysts toward sustainable hydrogen production.