One-step gas-phase syntheses of few-layered single-phase Ti₂NCl₂ and Ti₂CCl₂ MXenes with high stabilities

With the iteration of etching techniques, MXenes have exhibited astounding accomplishments. Nevertheless, intricate procedures, expensive precursors, and degradation present obstacles for practical application. Although chemical vapor deposition has been developed as a solution, direct syntheses of few-layered single-phase MXenes remain an open challenge, especially for Ti₂NCl₂. Here, we propose a one-step gas-phase synthetic method to fabricate few-layered single-phase Ti₂NCl₂ and Ti₂CCl₂. Design of the activation section and segregation from the synthetic zone are the key factors. The reaction paths, synthetic mechanism, and degradation behavior are revealed. Due to the low proportion of Ti vacancies, the time constant of the Ti₂CCl₂ solution is 73 times longer than that of Ti₂CCl_x. Furthermore, the specific capacity for Li⁺ storage with Ti₂NCl₂ is 1.37 times greater than that of Ti₂CCl₂. The one-step gas-phase method will accelerate practical application of MXenes.