Room Temperature NH ₃ Sensors with Enhanced Sensitivity Based on Ti ₃ C ₂ T _<i>x</i> MXene/ZnO Heterostructures

Developing highly sensitive, selective, fast response, and long-term stable room-temperature ammonia (NH3) sensors based on MXene materials remains a key challenge for their practical application. Here, Ti3C2Tx MXene/ZnO composites with varying mass ratios (3:1, 2:1, 1:1, and 1:2) were synthesized through a straightforward one-step hydrothermal route. Characterization using XRD, SEM, energy-dispersive X-ray spectroscopy (EDS), and X-ray photoelectron spectroscopy (XPS) confirmed the successful formation of the composites, revealing surface chemical bonding and electron transfer. Gas-sensing evaluations indicated that the Ti3C2Tx/ZnO composites at a 2:1 mass ratio exhibited the best performance at a relative humidity of 40% and room temperature, achieving a remarkable response of 828% for 300 ppm NH3. Moreover, it maintained a significant and detectable response of 32% even at a much lower concentration of 5 ppm NH3. Furthermore, the sensor exhibited quick response and recovery times of 26 and 11 s to 20 ppm NH3, respectively, significantly outperforming the pristine Ti3C2Tx MXene and ZnO sensors. Both experimental findings and density functional theory calculations verify that the improved performance stems from a synergistic effect: the accordion-like MXene structure provides an abundant adsorption site, while the incorporation of ZnO nanoparticles expands active surface areas and facilitates charge transfer through a p–n heterojunction. This work offers a prospective strategy for the targeted development of room-temperature-operating, high-sensitivity, and low-power gas sensors.