Vertically mounting molybdenum disulfide nanosheets on dimolybdenum carbide nanomeshes enables efficient hydrogen evolution

Designing hierarchical heterostructure to optimize the adsorption of hydrogen intermediate (H*) is impressive for hydrogen evolution reaction (HER) catalysis. Herein, we show that vertically mounting two-dimensional (2D) layered molybdenum disulfide (MoS₂) nanosheets on 2D nonlayered dimolybdenum carbide (Mo₂C) nanomeshes to form a hierarchical heterostructure largely accelerates the HER kinetics in acidic electrolyte due to the weakening adsorption strength of H* on 2D Mo₂C nanomeshes. Our hierarchical MoS₂/Mo₂C heterostructure therefore gives a decrease of overpotential for up to 500 mV at −10 mA·cm⁻² and an almost 200-fold higher kinetics current density compared with the pristine Mo₂C nanomeshes and maintains robust stability with a small drop of overpotential for only 16 mV upon 5,000 cycles. We further rationalize this finding by theoretical calculations and find an optimized adsorption free energy of H*, identifying that the MoS₂ featuring strong H* desorption plays a key role in weakening the strong binding of Mo₂C with H* and therefore improves the intrinsic HER activity on active C sites of Mo₂C. This present finding shines the light on the rational design of heterostructured catalysts with synergistic geometry.