Synthesis of Ti3C2Tx/ZnO composites decorated with PEDOT:PSS for NO2 gas sensors

This study aimed to synthesize Ti3C2Tx (MXene) through selective etching of Ti3AlC2 (MAX) using the in situ hydrofluoric acid method. ZnO was then grown on the Ti3C2Tx surface to form Ti3C2Tx (MXene)/ZnO composites (M-ZnO) using the hydrothermal method. To increase adhesion between the M-ZnO sensing composite and the laser-patterned interdigitated electrode surface, PEDOT:PSS was used as an adhesive layer to obtain PEDOT:PSS/M-ZnO-based gas sensors. The surface morphology, cross-sectional profile, elemental analysis, and structural and chemical compositions of M-ZnO composites were characterized using scanning electron microscope with energy-dispersive X-ray spectroscopy, X-ray diffractometer, X-ray photoelectron spectroscopy, and Fourier transform infrared spectroscopy. The results of the sensing test indicated that the responses of the gas sensors were 3.66%, 6.62%, 8.12%, and 10.23% when PEDOT:PSS/M-ZnO were exposed to 400, 600, 800, and 1000 ppb NO2 concentrations, respectively. The sensitivity of the PEDOT:PSS/ZnO-, PEDOT:PSS/MXene-, and PEDOT:PSS/M-ZnO-based gas sensors was 0.67, 1.37, and 10.61, respectively. The PEDOT:PSS/M-ZnO-based gas sensor had the highest sensitivity of 10.61, which was 15.8 times higher than the PEDOT:PSS/ZnO-based gas sensor. Additionally, the PEDOT:PSS/M-ZnO-based gas sensor displayed good stability and excellent sensing selectivity for NO2 gas at room temperature.