Room-temperature humidity-resistant highly sensitive ammonia sensor based on a porous MXene/Na2Ti3O7 @polyaniline composite

Two-dimensional MXenes exhibit excellent sensing performance for gaseous ammonia at room temperature; nevertheless, their widespread usefulness is somewhat limited because they are oxidizable and poorly moisture resistant. In this study, MXene-derived sodium titanate (Na2Ti3O7) nanofibers were hydrothermally grown on MXene surfaces and then encapsulated by polyaniline (PANI) via polymerization. The resulting MXene/Na2Ti3O7 @PANI composite is humidity resistant and highly sensitive to gaseous NH3 at room temperature. The Na2Ti3O7 nanofibers prevent MXene-layer stacking and provide more active sites for gas absorption, whereas PANI inhibits MXene oxidation and enhances moisture resistance. The MXene/Na2Ti3O7 @PANI-composite-based gas sensor is highly sensitive (185.44%) to 100 ppm NH3 at 45% RH. Interestingly, the sensor response was observed to improve with increasing humidity (30-90% RH range); a relative response of 283.8% was obtained at 90% RH along with a low detection limit of 186 ppb. The sensor still detected 91.1% of its initial value after 30 d, highlighting its stability. The prepared MXene/Na2Ti3O7 @PANI composite is a promising highly sensitive NH3 detector even under high-humidity conditions.