Enhanced low-temperature sensitivity of H2S gas sensing via oxygen vacancy-rich NiO-SnO2 heterojunction nanostructures

The detection of low concentration hydrogen sulfide (H 2 S) gas is of paramount importance for environmental safety and human health, given its colorless, toxic, and flammable nature. In this study, heterostructure material composed of SnO 2 nanorods modified with NiO nanosheets were synthesized, which significantly improved the detection performance of the sensor for hydrogen sulfide (H 2 S) gas at low temperatures by combining the interaction between oxygen vacancies and built-in electric fields. The formation of heterojunctions was verified using X-ray diffraction (XRD) and transmission electron microscopy (TEM), and the existence of oxygen vacancies was further confirmed through electron paramagnetic resonance (EPR) spectroscopy. The heterojunction sensor, when modified with 3 mol% NiO, exhibited an exceptional response value of 386 towards 10 ppm H 2 S at 125 °C, with a rapid response time of 6 s, surpassing that of the pristine SnO 2 sensor. This superior performance can be attributed to the synergistic effect of oxygen vacancies between SnO 2 and NiO, along with the inherent electric field present in the heterojunction. The study showcases the remarkable selectivity and long-term stability of this sensor in detecting hydrogen sulfide gas, offering innovative insights for the advancement of low-temperature and highly sensitive H 2 S gas sensors.