Investigating the Annealing Effects of Ti₃C₂T_X MXene for Stable and Selective Low-Concentration Hydrogen Detection

Titanium carbide (Ti 3 C 2 T X ), a member of the MXene family, is widely used in diverse applications, which include gas sensors, energy storage, electrochromic devices, biosensors, etc. However, its effectiveness in gas sensing is notably lacking, indicating the need for further research in this field. This study investigates a detailed analysis of the effects of annealing on pristine titanium carbide, particularly emphasizing its ability to detect H 2 selectively. Annealing Ti 3 C 2 T X at 300 °C in the presence of air results in the formation of partially oxidized MXene (Ti 3 C 2 T X /TiO 2 ), which enhances conductivity and yields a response of 62 ± 5% to 4% H 2 and 6.6% to 50 ppm of H 2, with a response time of less than 1 min. In contrast, pure Ti 3 C 2 T X shows a reduced conductivity and a weak response of 1.0%. The 300 °C annealed MXene sensor, with its operating temperature optimized at 300 °C, exhibits a strong selectivity toward H 2 compared to CH 4, NH 3, and CO due to the combined properties of MXene and TiO 2 . In addition, the instability issues within the pristine MXene contribute to its diminished sensitivity, and an effective enhancement can be realized through variation of the annealing temperatures. A detailed investigation was carried out to understand the underlying mechanisms influencing gas sensing in partially oxidized MXene, emphasizing structure-based depletion layer formation using detailed material characterization techniques, including X-ray photoelectron spectroscopy, thermogravimetric analysis, and X-ray diffraction. Finally, the sensor prototype is assembled by combining a microheater and an interdigitated electrode with the optimized sensing material inside the TO8 package.