Green, HF-Free Synthesis of MXene Quantum Dots and their Photocatalytic Activity for Hydrogen Evolution.

Abstract

A general methodology to prepare MXene quantum dots (MxQDs) with yields over 20% by liquid-phase laser ablation of the MAX phase is reported. Mechanical and thermal shock by 532nm laser pulses (7ns fwhp, 50mJ × pulse-1 , 1Hz pulse frequency) produces MAX etchingandexfoliationtoformMXene QDs, avoiding the use of HF. The process can be followed by absorption and emission spectroscopy and by dynamic laser scattering and it appears to be general, being applied to Ti3 AlC2 , Ti2 AlC, Nb2 AlC, and V2 AlC MAX phases. Densityfunctionaltheory calculations indicate that, depending on the surface terminal groups, the diminution of the MXene size to the nanometric scale makes it possible to control the band gap of the MXene. The photocatalytic activity of these MXene QDs for hydrogen evolution has been observed, reaching an H2 production for the most efficient Ti3 C2 QDs as high as 2.02 mmol × g-1 × h-1 .