Lattice distortion and cation vacancy decorated V2-xCTy MXene quantum dots anchored on porous g-C3N4 nanotubes for efficient photocatalytic hydrogen evolution.

The synergistic coupling between vacancy defects and lattice distortions in photocatalysts substantially accelerates the separation and transport kinetics of photogenerated carriers. Herein, we report a highly efficient photocatalyst toward the hydrogen evolution reaction (HER), which is fabricated by confining V2-xCTy MXene quantum dots (QDs) with abundant vanadium vacancies (VV) and prominent lattice distortions within porous g-C3N4 nanotubes (GCN NTs). The optimized photocatalyst affords a visible-light-driven H2 evolution rate of 0.40 mmol∙h-1 along with a corresponding apparent quantum yield (AQY) of 21.67%, which is four-fold higher than that of pristine porous GCN NTs. Such superior photocatalytic performance originates from the intimate interfacial coupling between the lattice-distorted and VV-rich V2-xCTy MXene QDs and porous GCN NTs. This unique heterostructure constructs a robust internal electric field (IEF), which efficiently promotes spatial charge separation and extends the photogenerated carrier lifetime. Density functional theory (DFT) calculations further verify that the synergistic effect between VV defects and lattice distortions in confined V2-xCTy MXene QDs not only optimizes the adsorption behavior of key reaction intermediates but also maximizes the exposure of unsaturated active sites, thereby significantly reducing the kinetic barrier of the HER. Collectively, this work systematically clarifies the synergistic mechanism of vacancy defects and lattice distortions in MXene QDs, providing a feasible strategy for the rational design and fabrication of high-efficiency photocatalysts.