Abstract: Hydrogen energy, as one of the most promising clean energy vectors in the 21st century, has positioned its efficient production technology as a critical pathway for global energy transition. However, large-scale implementation of water electrolysis remains constrained by the high overpotentials of hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), resulting in inefficient energy conversion. Although noble-metal-based catalysts (Pt, IrO2/RuO2) exhibit exceptional catalytic activity, their scarcity and prohibitive costs severely restrict industrial deployment. Transition metal sulfides (TMS) have emerged as competitive alternatives to noble-metal catalysts due to their cost-effectiveness and tunable electronic structures, yet their inferior intrinsic activity hinders large-scale applications. Metal-organic frameworks (MOFs), featuring ordered porous architectures, high specific surface areas, and uniformly distributed metal nodes, can be converted through controlled sulfurization into cobalt-based sulfides with hierarchical porosity. This conversion not only preserves the three-dimensional skeletal advantages of the precursors but also effectively modulates the density of states at metal centers via sulfur-atom doping. In this work, ZIF-67 is employed as a precursor to construct a hollow-structured Ni0.3Co2.7S/MoS2 flower-like composite catalyst through sulfur-induced Kirkendall effect-driven synthesis. The hollow framework of the composite synergistically enhances cycling stability by effectively anchoring MoS2 nanosheets, while its expanded interlayer spacing facilitates sufficient electrolyte infiltration and optimizes charge transfer pathways. The Ni0.3Co2.7S/MoS2 catalyst demonstrates exceptional electrocatalytic hydrogen evolution performance, achieving a low overpotential of 150 mV at 10 mA cm-2. Remarkably, after galvanostatic stability testing (80 h at 10 mA cm-2) and 2000 cyclic voltammetry cycles, the overpotential increases by only 7 mV, highlighting its superior activity and long-term durability. This study provides a novel strategy for designing efficient and stable TMS-based electrocatalysts for water splitting, offering significant scientific value for advancing green hydrogen technologies.

Key words: Hydrogen evolution reaction, Transition metal sulfides, Structural engineering, Hydrothermal synthesis