Terminal-group engineering of p-type Nb₂CT_x MXene for enhanced thermoelectric and sensing performance

Boasting high electrical conductivity and customizable surface terminal groups, MXenes are considered to have broad application prospects in the field of thermoelectrics. The thermoelectric performance of n-type MXenes, such as Ti₃C₂T_x and Mo₂TiC₃T_x, has been significantly improved through regulation strategies and has consequently been applied to tactile, respiratory, and stress sensing, among other areas. However, the preparation and regulation of high-performance p-type MXenes remain a significant challenge. This study focused on the p-type MXene Nb₂CT_x. Using a simple annealing process and XPS semi-quantitative analysis, this work investigated how the ratio of surface terminal groups affects the thermoelectric properties of Nb₂CT_x nanosheets. The removal of strongly electronegative terminal groups led to the release of localized electrons and a reduction in interlayer spacing. This resulted in a Seebeck coefficient of 28.9 μV K^-1, while the electrical conductivity increased sixfold (to 41.47 S cm^-1), and the power factor correspondingly rose to 3.45 μW m^-1 K^-2. Furthermore, this work explored its response sensitivity and stability as a touch sensor. These findings highlight the potential of the terminal group regulation strategy in advancing the development of MXene-based thermoelectric materials.