Room Temperature Ionic Liquid-Gated Carbon Nanotube FETs for Stable Hydrogen Sensing at Elevated Temperatures

A novel hydrogen sensor, harnessing the synergy of room temperature ionic liquid (RTIL) and carbon nanotube field-effect transistors (CNT FETs), is proposed to improve the stability and long-term reliability of gas sensors. Utilizing RTIL as an electrolyte gate dielectric enhances sensitivity and markedly improves stability under elevated temperatures and harsh environmental conditions. The sensor maintains a low subthreshold slope (SS ≈ 100 mV/dec) and a stable on/off ratio (>10⁴) after long-term operation at 80°C. At 1000 ppm H₂, it exhibits a strong response of 86%, with rapid response/recovery times of 76/230 s. Selectivity measurements show negligible responses to 10 ppm NO₂, NH₃, and H₂S (<16%), indicating good anti-interference performance. Nernst equation analysis highlights the role of the RTIL/metal interface electric double layer (EDL) in modulating sensing process. Additionally, the T ₉₀ response time of the sensor decreases from 246 s at 23°C to 76 s at 80°C, demonstrating accelerated hydrogen diffusion at higher temperatures, consistent with a diffusion-controlled model. The sensor was also applied for real-time hydrogen monitoring during lithium-ion battery thermal runaway, where it quickly and accurately detected hydrogen leakage, showcasing its potential in elevated temperature environments. These findings underscore the key role of the RTIL gate in improving sensor performance and reliability, providing both theoretical and practical support for the future use of RTIL-CNT FET gas sensors.