High-performance NO2 gas sensor enabled by Fe, N co-doped GQDs modification and pulse-driven temperature modulation

Nitrogen dioxide (NO2) is a typical reactive nitrogen species harmful to health and the environment. However, NO2 sensors still suffer from low sensitivity and poor response/recovery rates. Herein, 3D In2O3 assembled by stacked nanosheets were prepared and modified with N element-doped GQDs (N-GQDs) and Fe, N co-doped GQDs (Fe,N-GQDs), respectively. The results of NO2-sensing performance indicated that the optimal sample (0.3 wt% Fe,N-GQDs/In2O3) showed a high response of 414.5 to 1 ppm NO2 and could detect as low as 10 ppb at 50℃, which was 1.3 and 4.0 times higher than that of 0.3 wt% N-GQDs/In2O3 and In2O3, respectively. The gas-sensing kinetics were analyzed by establishing gas adsorption/desorption isotherms. The enhanced NO2 sensing properties of 0.3 wt% Fe,N-GQDs/In2O3 were mainly due to the enhanced active site accessibility of stacked nanosheets with open layer spaces, the heterointerface between Fe,N-GQDs and In2O3, and electrical modulation of Fe,N-GQDs. Additionally, A pulse-driving circuit was designed for a pulse temperature modulation (PTM) strategy to further boost NO2 detection. The sensor response is further enhanced by 1.7 times, and the response/recovery time is reduced by 42.5%/60.1%. The NO2 concentration in vehicle exhaust was determined using PTM mode with good spike recoveries. It validated the reliability of the sensor for the quantitative detection of NO2 in the real environment. This work provides insights into sensor design and has the potential to contribute to the development of novel sensing platforms for other gas pollutants.