Coupled electronic and phononic transport in O-terminated MXene nanoribbons within a unified TB-NEGF framework

Thermoelectric transport in oxygen-terminated MXene nanoribbons is investigated using a tight-binding nonequilibrium Green’s function (TB-NEGF) framework combined with phonon transport calculations. Ti₃C₂O₂ is considered as the primary system, and the effect of thermally induced bond-length fluctuations on electronic hopping parameters is incorporated through a temperature-dependent hopping-renormalization scheme. The present model is intended as a computationally efficient effective description, with the force constants and hopping-decay coefficients treated as effective parameters. At 300 K, the maximum electronic thermoelectric figure of merit changes from 2.9698 for the unrenormalized system to 2.9944 after hopping renormalization, indicating a relatively small effect of thermal lattice fluctuations on the electronic thermoelectric response. The phonon contribution is subsequently evaluated using phonon NEGF, yielding a lattice thermal conductance of 2.57 × 10⁻¹¹ W K⁻¹ and a corresponding thermal conductivity of 0.0411 W m⁻¹ K⁻¹. Including lattice thermal transport reduces the maximum ZT to 0.8361. Comparative calculations for Zr₃C₂O₂ show that the proposed treatment can also be applied to a different transition-metal-based MXene. These results demonstrate that lattice heat transport, rather than thermal hopping renormalization, plays a major role in determining the achievable thermoelectric performance of the investigated MXene nanoribbons.