Synthesis and characterization of a new out-of-plane ordered double-transition-metal MAX phase, Mo2VAlC2, and its two-dimensional derivate Mo2VC2Tx MXene

Herein we demonstrate the synthesis of a new out-of-plane ordered double-transition-metal MAX phase known as Mo 2 VAlC 2 . Annealing the elemental powder mixture at 1540 °C with 2.0Mo: 1.0 V: 1.3Al: 1.8C results in a high yield of 91.2 wt% for Mo 2 VAlC 2 . The crystal structure of Mo 2 VAlC 2 is determined using Rietveld refinement of powder XRD, and which crystalizes into a hexagonal lattice structure with space group P6 3 /mmc. Employing the double spherical aberration corrected transmission electron microscopy, we confirm its chemically ordering behavior of one V layer sandwiched between two Mo layers. Additionally, its two-dimensional derivative Mo 2 VC 2 T x MXene has been successfully realized by etching the Al layer of Mo 2 VAlC 2 with hydrofluoric acid. The chemical composition and microstructure of Mo 2 VC 2 T x are inspected with SEM and EDX. The resulting multilayer and intercalated Mo 2 VC 2 T x exhibit the characteristic accordion-like and paper-like appearances, respectively. This work further expands the diversity of chemically ordered double-transition-metal MAX and MXene families.