Rapid and scalable combustion synthesis of (Mo2/3Y1/3)2AlC i-MAX as the precursor for vacancy-ordered MXene

• Scalable synthesis of (Mo 2/3 Y 1/3 ) 2 AlC i- MAX phase via self-propagating high-temperature synthesis (SHS) in under one minute without external energy input. • Product yield increased to 73.6% through the use of AlY 2.3 master alloy. • Study of reaction kinetics shows how the use of the master alloy increases the phase purity. • MXene yield approximately doubled compared to conventional synthesis methods. For MXenes to be viable in commercial and industrial applications, their production must rely on processes that are energy-efficient, environmentally sustainable, and scalable. A critical factor influencing this viability is the synthesis route of the parent MAX phase. In this study, we report a novel and rapid approach for synthesizing a chemically ordered MAX phase ( i- MAX), specifically the in-plane ordered (Mo 2/3 Y 1/3 ) 2 AlC, using self-propagating high-temperature synthesis (SHS) completed in one minute. The target MAX phase yield was estimated using Rietveld refinement to be 73.6% with the main impurity phases identified as Mo 3 Al 2 C and YF 3 . Thermodynamic calculations combined with experimental characterizations indicate that the use of an aluminum–yttrium master alloy played a pivotal role in achieving high synthesis yield by facilitating a sequence of intermediate phase transformations that enhance reaction kinetics and i- MAX formation. This method involves the utilization of Poly(tetrafluoroethylene)—(C 2 F 4 ) n as a promoter, which enables the formation of volatile fluorides or fluorine-containing intermediates, making the reaction self-sustaining. Etching and delamination of the SHS-produced i- MAX phase yielded a vacancy-ordered MXene with the formula Mo 4/3 CT x , with a yield value twice that obtained using the conventional MAX-phase parent material preparation route. This work demonstrates the method’s effectiveness in achieving rapid, straightforward, and energy-efficient synthesis of a diverse range of MAX and i- MAX phases, thereby paving the way for scalable and efficient MXene production.