Ti3C2 MXene-Based Composites for Hydrogen and Ammonia Gas Sensing: A Review

The unique contributions of 2D Ti3C2 MXenes surface, electrical, and chemical features play a crucial role in determining toxic and flammable gas-sensing behavior. Specifically, its high electrical conductivity (metallic nature), layered nanosheet structure (nanosheets), and surface termination groups (−O, −F, and −OH) collectively contribute to excellent hydrogen (H2) and ammonia (NH3) gas-sensing behavior. This review systematically explores the impact of pristine and modified Ti3C2 MXene, including its interfaces with various metals and metal oxides for enhancing H2 and NH3 detection. Furthermore, the significance of room temperature operation and flexible gas sensing mechanisms is explored. Notably, integration of Ti3C2 MXene and sulfur nanosheets demonstrates rapid response and recovery times with detection limits at ppt level. Ti3C2 MXene-based interfaces also exhibit excellent long-term stability under various relative humidity conditions. The selective surface termination groups (−OH and −O) facilitate the formation of hydrogen bonds with NH3 molecules for enhancing gas adsorption and sensing selectivity. In addition, the expansion of the interlayer spacing plays a vital role in improving the gas-sensing performance. Partial oxidation of Ti3C2 MXene into TiO2 increases the interlayer distance, promoting faster diffusion of gas molecules and quicker sensor response. Overall, the intrinsic properties of Ti3C2 MXene and its composites significantly achieve high-performance room-temperature H2 and NH3 gas-sensing performance.