Methods for the synthesis and alkyl-functionalization of mxenes

A two-dimensional transition metal carbide MXene having a formula Mn+1Cn (T′T″1-y)x, where 1≤n≤4, M is one or more early transition metal elements, T′ and T″ represent two different halogen atoms, and 0<y<1.

A method of alkylating a two-dimensional transition metal MXene having a formula Mn+1XnTx, where 1≤n≤4, M is one or more early transition metal elements, X is carbon or nitrogen, and Tx are surface terminating halogen atoms, the two-dimensional transition metal MXene comprising a stack of monolayer MXene sheets, the method comprising:

• electrochemically reducing the two-dimensional transition metal MXene having the formula Mn+1XnTx in an electrolyte solution comprising an alkyl group-functionalized quaternary organic cation in a polar aprotic solvent, wherein the electrochemical reduction drives intercalation of the alkyl group-functionalized quaternary organic cation between the monolayer MXene sheets and the formation of an ionic quaternary organic cation-MXene compound;
• and
• replacing the polar aprotic solvent with a non-polar solvent to induce a carbocation transfer between alkyl groups on the alkyl group-functionalized organic cation and early transition metal atoms of the two-dimensional transition metal MXene to form the alkylated two-dimensional transition metal MXene.

An alkylated two-dimensional transition metal MXene having a formula Mn+1XnTx, where 1≤n≤4, M is one or more early transition metal elements, X is carbon or nitrogen, and Tx are surface terminating atoms or groups, wherein at least some of the surface terminating atoms or groups are alkyl groups covalently bonded in M atoms of the MXene via C-M bonds.