Reducing kinetic energy barriers and developing accessible active sites are critical to deliver high hydrogen evolution reaction (HER) efficiency. In this paper, we synthesized defect-modulated and heteroatom (boron)-functionalized three-dimensional (3D) bowl-shaped Ti_3−xC₂T_y MXene (B-TCT) nanocavities coupled with the vertical growth of MoSe₂ nanoflakes. The B-TCT@MoSe₂ nanohybrids catalyst delivers the overpotentials of 49.9, 52.7, and 67.8 mV to reach a HER current density of 10 mA·cm⁻² under acidic, alkaline, and neutral conditions, respectively. Such outstanding HER activity is predominantly attributed to the heteroatom functionalization, self-adapting Ti vacancy (V_Ti) defect modulation, and spatial configuration design in the 3D B-TCT nanocavity, which synergistically regulate the electronic structure, activate the basal plane/edge unsaturated sites, and reduce the reaction energy barrier. Experimental and theoretical calculations demonstrate that strong heterogeneous interfacial bonding interactions between B-TCT and MoSe₂ can dramatically reduce the free energy of hydrogen adsorption and facilitate efficient interfacial charge migration, thus essentially improving the HER kinetics. We used this 3D porous nanohybrid system assembled by defect-rich lamellar structures to elucidate the advantageous synergistic effects of multiple mechanisms among defect structure, heteroatom functionalization, and interfacial coupling, which provided important insights for the development of efficient hybrid-type catalysts.

Electronic modulation on the inert basal plane of transition-metal dichalcogenides(TMDs) through vacancy defect excitation, although extremely challenging, is urgent for understanding the factors that impact the hydrogen evolution reaction (HER) catalytic activity. Here, ultrathin WS₂ nanosheets with precise quantitative single atomic S-vacancy on the inert basal plane were flexible prepared through hydrogen peroxide etching strategy. The as-synthesized single atomic S-vacancy defect WS₂ (SVD-WS₂) nanoflake with the activated basal plane exhibited an impressive overpotential of 137 mV at a current density of 10 mA·cm^-2 and a Tafel slope of 53.9 mV·dec^-1. Furthermore, anchoring on the defect graphene matrix, the assembled two-dimensional (2D) stacking heterojunction exhibits further enhanced HER catalytic activity (an overpotential of 108 mV vs. 10 mA·cm^-2 and a Tafel slope of 48.3 mV·dec^-1) and stability (~ 10% decline after 9, 000 cycles), which attributed to the electronic structure modulation from the synergetic interactions between SVD-WS₂ and defect graphene. Our finding provides a smart defects introduce strategy to trigger high-efficiency hydrogen evolution over WS₂ nanosheets and a general 2D heterojunctions fabricated inspiration based on strong interaction interface.