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

A unique V 2-x CT y QDs@GCN photocatalyst for H 2 evolution. • The lattice-distorted and V V decorated V 2-x CT y MXene QDs provides abundant active sites. • The interfacial electric field of photocatalyst promotes fast charge transfer. • The H 2 evolution rate of the best V 2-x CT y QDs@GCN photocatalyst is 0.4 mmol h −1 . • The V 2-x CT y QDs@GCN photocatalyst shows a high AQY of 21.67% at 383 nm. 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 V 2-x CT y MXene quantum dots (QDs) with abundant vanadium vacancies (V V ) and prominent lattice distortions within porous g-C 3 N 4 nanotubes (GCN NTs). The optimized photocatalyst affords a visible-light-driven H 2 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 V V -rich V 2-x CT y 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 V V defects and lattice distortions in confined V 2-x CT y 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. The lattice-distorted and V V decorated V 2-x CT y QDs anchored on porous g-C 3 N 4 NTs enable effective charge separation, provide abundant active sites, reduce the adsorption energy barrier and construct stable bonding interface, thus achieving high-efficiency photocatalytic H 2 evolution. Download: Download high-res image (166KB) Download: Download full-size image