An in-plane Co₉S₈@MoS₂ heterostructure for the hydrogen evolution reaction in alkaline media

Transition metal sulfides have emerged as promising hydrogen evolution reaction (HER) electrocatalysts in acidic media due to high intrinsic activity. They exhibit inferior HER activity in alkaline media, however, owing to the sluggish water dissociation kinetics. Herein, in-plane MoS₂/Co₉S₈ heterostructures are in situ grown on three-dimensional carbon network substrates with interconnected hierarchical pores by one-step pyrolysis to enhance the alkaline HER activity. The experiment results reveal that the HER kinetics of MoS₂ is accelerated after the construction of heterostructures. The synthesized MoS₂/Co₉S₈ heterostructures anchored on a three-dimensional interconnected hierarchical pore carbon network exhibit a lower overpotential of 177 mV than MoS₂ (252 mV) at 10 mA cm^-2 for the HER in 1 M KOH. The enhanced catalytic performance is mainly attributed to the accelerated water dissociation kinetics on the interface of MoS₂ and Co₉S₈. In combination with DFT calculations, it is revealed that assembling the interface construction synergistically favors the chemisorption of protons and the cleavage of the O-H bonds of the H₂O molecule, thus accelerating the kinetics of the HER. Moreover, the three-dimensional interconnected hierarchical pore carbon (3DC) network structure is beneficial for the circulation of the electrolyte and H₂ spillover. This study demonstrates the present strategy as a facile route for fabricating efficient HER catalysts.