d-Band Center Optimization of Ti3C2T x MXene Nanosheets for Ultrahigh NO2 Gas Sensitivity at Room Temperature

MXene exhibits numerous advantageousproperties such as high electronicconductivity, high surface area, and ease of surface modificationvia tailoring of functional groups. However, the mechanism by whichMXene functionalization enhances gas sensing performance has not yetbeen well understood, let alone the development of a rational sensordesign optimization strategy. This work presents a functionalizationmethodology for MXene based on d-band center modulation, which canbe implemented by introducing Fe onto the surface of Ti3C2T x nanosheets, for significantlyimproved gas sensing response and selectivity. The strategy is demonstratedin the design of gas sensors. The optimized gas sensor shows a responseof 50% toward 10 ppm of NO2 at room temperature, whichis over 6-fold improvement from its pristine counterpart, an unprecedentedperformance level among all reported MXene gas sensors. XPS characterizations,valence band analyses, and density functional theory (DFT) calculationsall indicate that the underlying enhancement mechanism can be attributedto the tuning of the d-band center energy toward the Fermi level.This work provides a new design strategy based on the optimizationof the d-band center energy and adds a much needed systematic andquantitative method to the design of two-dimensional materials basedsemiconducting gas sensors.

Automated summary

This work presents a functionalization methodology for MXene based on d-band center modulation, which significantly improves gas sensing response and selectivity. The optimized gas sensor shows unprecedented performance among all reported MXene gas sensors, with a response of 50% toward 10 ppm of NO2 at room temperature.