M<sub>5</sub>X<sub>4</sub>: A Family of MXenes.
basic_science · Level V
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- Record sourced from PubMed, PMID 37650585.
- Also identified by DOI 10.1021/acsnano.3c04967.
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Abstract
MXenes are two-dimensional (2D) transition metal carbides, nitrides, and carbonitrides typically synthesized from layered MAX-phase precursors. With over 50 experimentally reported MXenes and a near-infinite number of possible chemistries, MXenes make up the fastest-growing family of 2D materials. They offer a wide range of properties, which can be altered by their chemistry (M, X) and the number of metal layers in the structure, ranging from two in M<sub>2</sub>XT<sub><i>x</i></sub> to five in M<sub>5</sub>X<sub>4</sub>T<sub><i>x</i></sub>. Only one M<sub>5</sub>X<sub>4</sub> MXene, Mo<sub>4</sub>VC<sub>4</sub>, has been reported. Herein, we report the synthesis and characterization of two M<sub>5</sub>AX<sub>4</sub> mixed transition metal MAX phases, Ti<sub>2.5</sub>Ta<sub>2.5</sub>AlC<sub>4</sub> and Ti<sub>2.675</sub>Nb<sub>2.325</sub>AlC<sub>4</sub>, and their successful topochemical transformation into Ti<sub>2.5</sub>Ta<sub>2.5</sub>C<sub>4</sub>T<sub><i>x</i></sub> and Ti<sub>2.675</sub>Nb<sub>2.325</sub>C<sub>4</sub>T<sub><i>x</i></sub> MXenes. The resulting MXenes were delaminated into single-layer flakes, analyzed structurally, and characterized for their thermal and optical properties. This establishes a family of M<sub>5</sub>AX<sub>4</sub> MAX phases and their corresponding MXenes. These materials were experimentally produced based on guidance from theoretical predictions, leading to more exciting applications for MXenes.