Ni-doped MnO₂/Ti₃C₂T_x MXene nanocomposite for highly sensitive electrochemical ammonia gas sensing at room temperature

Highly sensitive ammonia (NH₃) gas sensors play a critical role in various industries due to their direct implication for health and safety. Nanocomposites have gained massive attention for recent electrochemical gas sensing. In this work, we first propose a Ni-doped MnO₂/Ti₃C₂T_x MXene nanocomposite material for electrochemical NH₃ gas sensing at room temperature. Ni-doped MnO₂ nanowires were introduced to Ti₃C₂T_x MXene using a self-assembly technique to develop a high-performance gas sensor. The nanocomposite was characterized using BET, SEM-EDS, XRD, and XPS analyses, which revealed that the Ni-MnO₂ nanowires were uniformly distributed on the MXene surface, significantly increasing the surface area. The Ni-MnO₂/Ti₃C₂T_x MXene nanocomposite was immobilized on a screen-printed carbon electrode (SPCE), which is the most appropriate platform for portable and convenient electrochemical sensors, and ionic liquid was used as an electrolyte to achieve high stability. Electrochemical analysis showed that this new NH₃ gas sensor had outstanding performance with a higher sensitivity and a lower detection limit of 0.072 µA/ppm and 0.23 ppm, respectively. It also exhibited a fast response time of 45 s at 20 ppm NH₃ gas, high repeatability, selectivity, and long-term stability. In addition, the electrochemical NH₃ gas nanosensor was successfully demonstrated to monitor food freshness.