Minutes‐Fast Production of Vacancy‐Enriched MXenes as an Efficient Platform for Single‐Atom Electrocatalysts

Abstract Although MXenes have been synthesized by liquid phase and molten salt etching approaches, it still suffers from sluggish reaction kinetics of removing A species from MAX phases associated with an overlong production time (5–48 h). Here, a minute‐level production approach is developed to produce MXenes (Ti 2 CCl x ) by selectively etching MAX phases (Ti 2 AlC) under metal chloride (ZnCl 2 ) vapor. In this synthetic protocol, metal chloride vapor possesses a very high chemical activity to the interlaminar A metal layers of MAX phases owing to negative Gibbs free energies, accompanied with the fast removal of gaseous A‐containing chlorides in the reaction system. Moreover, some M species can be controllably etched off from the lattice of MX slabs to generate metal vacancies, which have a high reducing ability to implant single‐atom Zn from ZnCl 2 vapor. Finally, vacancy‐enriched MXenes are produced after the volatilization of Zn. In this manner, the etching time is less than one‐sixtieth those of liquid phase and molten salt etching approaches. The resultant MXenes can be employed as an efficient platform for implanting single‐atom Pt, showing a low overpotential of 41 mV at a current density of 10 mA cm −2 and a good long‐term stability up to 5000 cycles.