Figure 19.

(a) SEM image of N-MXene; (b) TEM image of N-MXene; (c) SEM image of rGO/N-MXene/PEI composites; (d) TEM image of rGO/N-MXene/PEI composites; (e) XRD spectra; (f) FTIR study of MXene, N-MXene, and rGO/N-MXene/PEI hybrid; (g) elemental mapping of N-MXene and (h) rGO/N-MXene/PEI nanocomposites; resistance transients of sensors (i) MXene, (j) N-MXene, (k) rGO/N-MXene, (l) rGO/PEI, (m) N-MXene/PEI, and (n) rGO/N-MXene/PEI sensors for 1000 CO₂ in 48% (relative humidity) RH air at room temperature (20 °C); (o) dry and (p) humidified dynamic resistance of the composite (ternary) sensor at 20 °C under 600 ppm CO₂; sensing performance of the ternary sensor: (q) Response toward a mixture of 600 ppm CO₂ and under varying RH, response as a function of RH obtained from (r–t) response to pure 48% RH at 20 °C and schematic representation of the CO₂ sensing mechanism of rGO/N-MXene/PEI sensors under dry and wet air respectively. Reproduced with permission from [164].