Synthesis of Three\nIsoelemental MXenes and Their Structure–Property\nRelationships

The MXene family has rapidly expanded since its discovery\nin 2011\nto include nearly 50 unique MXenes, not accounting for solid solutions\nand diverse surface terminations. However, a question raised since\ntheir discovery has been: What is the effect of <i>n</i>? In other words, how does the number of layers affect the MXene\nproperties? To date, no direct study of the impact of <i>n</i> has been conducted due to the lack of isoelemental MXene compositions\nspanning more than two <i>n</i> values. Herein, we report\non a system of three MXenes with identical M-site chemistries, (Mo<sub>2/3</sub>V<sub>1/3</sub>)<sub><i>n</i>+1</sub>C<sub><i>n</i></sub>T<sub><i>x</i></sub> (<i>n</i> = 1, 2, and 3), allowing for the study of MXene structure–property\nrelationships across <i>n</i>, for the first time. Chemical\nanalysis of the samples shows complete and partial ordering of the\nM-elements in the <i>n</i> = 2 and 3 samples, respectively.\nWe show that sample stability gradually evolves as <i>n</i> is increased from 1 to 3, while electronic and electrochemical properties\nexhibit more significant changes in going from <i>n</i> =\n1 to 2 than from <i>n</i> = 2 to 3.