Thermoelectric properties of functionalized MXene structures

In this study, we have investigated the electronic and lattice thermal transport properties of oxygen terminated M₂CO₂ (where M=Ti, Zr, Hf, Sc) MXenes in two different functional configurations (Model-II and Model-III), in order to assess their thermoelectric potentials. We determined that the model-III (MD-III) configuration of Ti₂CO₂ and Zr₂CO₂ has the lowest thermal conductivity as compared to Hf₂CO₂ and Sc₂CO₂ with the same configuration. The model-II (MD-II) configuration of Hf₂CO₂ has the highest thermal conductivity value. We revealed that the absorption site of oxygen atom has a large impact on the electronic and thermal transport properties of MXenes. The thermal conductivity, Seebeck coefficient and zT coefficient may vary 40% depending on the structural model. For instance, the thermal conductivity is 40.58 W/(mK) for MD-II and 18.42 W/(mK) for MD-III of Ti2CO2 at T=300 K. This structural variety provides us an additional degree of freedom for modulating physical and chemical properties of MXenes, that can be exploited to design efficient thermoelectric devices. Among the considered MXenes, Ti₂CO₂ and Zr₂CO₂ in MD-III configuration were found to have much lower thermal conductivity.