Synthesis of Three Isoelemental MXenes and Their Structure–Property Relationships

The MXene family has rapidly expanded since its discovery in 2011 to include nearly 50 unique MXenes, not accounting for solid solutions and diverse surface terminations. However, a question raised since their discovery has been: What is the effect of <i>n</i>? In other words, how does the number of layers affect the MXene properties? To date, no direct study of the impact of <i>n</i> has been conducted due to the lack of isoelemental MXene compositions spanning more than two <i>n</i> values. Herein, we report on a system of three MXenes with identical M-site chemistries, (Mo_2/3V_1/3)_<i>n</i>+1C_<i>n</i>T_<i>x</i> (<i>n</i> = 1, 2, and 3), allowing for the study of MXene structure-property relationships across <i>n</i>, for the first time. Chemical analysis of the samples shows complete and partial ordering of the M-elements in the <i>n</i> = 2 and 3 samples, respectively. We show that sample stability gradually evolves as <i>n</i> is increased from 1 to 3, while electronic and electrochemical properties exhibit more significant changes in going from <i>n</i> = 1 to 2 than from <i>n</i> = 2 to 3.