Synthesis of Three Isoelemental MXenes and Their Structure-Property Relationships.

Abstract

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.