Thermoelectric technology enables the direct and reversible conversion of heat into electrical energy without air pollution. Herein, the stability, electronic structure, and thermoelectric properties of methoxy-functionalized M2C(OMe)2 (M = Sc, Ti, V, Cr, Y, Zr, Nb, Mo, Hf, Ta, and W) were systematically investigated using first-principles calculations and semiclassical Boltzmann transport theory. All MXenes, except those with M = Cr, Mo, and W, can be synthesized by substituting Cl- and Br-functionalized MXenes with deprotonated methanol, with stability governed by the M-O bond strength. Notably, semiconductors Sc2C(OMe)2 and Y2C(OMe)2 exhibit exceptionally high peak ZT values of 15.02 and 12.11 under n-type doping at 900 K, achieving a remarkable thermoelectric conversion efficiency of 53% at a temperature difference of 600 K, outperforming current high-performance thermoelectric materials. This superior performance is attributed to the weak electron-withdrawing nature of the methoxy group, which enhances nonbonding d electrons, combined with flat and degenerate band edges, and strong coupling between acoustic and optical phonons. Together, these features sustain a high Seebeck coefficient, improve electrical conductivity, and suppress lattice thermal conductivity. These findings present an effective organic functionalization strategy for designing high-performance MXenes for industrial applications and offer valuable insights for developing next-generation thermoelectric materials.
Keywords: MXene; first-principles calculation; methoxy functionalization; organic functionalization; thermoelectric.