Carbon Nanotubes Enhanced TiO<sub>2</sub>/g-C<sub>3</sub>N<sub>4</sub> as a Potential Nanocomposite Material for Impedance-Type Humidity Sensors

The development of high-performance humidity sensors based on nanotechnology has become critical for different applications. This work focuses on the fabrication and characterization of impedance-type humidity sensors based on graphitic carbon nitride, titanium dioxide, and carbon nanotubes. The prepared materials comprise g-C3N4, g-C3N4/TiO2, and g-C3N4/TiO2/CNTs, which have been synthesized through the co-precipitation method. The properties of the nanocomposites have been verified through different characterization techniques that confirm the phase composition and morphology. The humidity-sensing response of the prepared materials was tested within a humidity range of 11%–97% RH at different testing frequencies. The unique structure of synthesized materials combines the high surface area and hydrophilic active sites of both g-C3N4 and TiO2, in addition to the exceptional conductivity of CNTs. The g-C3N4/TiO2 humidity sensors demonstrated a significantly enhanced sensitivity of 2.2 MΩ/RH% compared to the bare g-C3N4-based humidity sensor, while the response and recovery are still challenging. The incorporation of conductive CNTs into the binary nanocomposite (g-C3N4/TiO2) improves the response kinetics with response and recovery times of 81 and 39 sec, respectively. Besides the improved response kinetics, the ternary structure also demonstrated excellent repeatability and low hysteresis.