Humidity-independent NO2 gas sensors based on ZnO-NiOFx nanocomposites and the synergistic humidity-immune effect of fluorine doped NiO

Clean, alternative energy sources, especially fuel cells, are gradually attracting global attentions while the produced toxic nitrogen dioxide (NO 2 ) is a greatly hazardous chemical impacting their energy efficiencies. Metal oxide semiconductors (MOS) hold significant promise as NO 2 sensors. However, intensive humidity interaction intensifies signal drifts and reliable response inhibitions under variable humidity conditions. In this study, we present a novel approach to address this issue by engineering in-situ F-doped NiO nanocomposites (NiOF x ) decorated on ZnO snowflakes achieved through decomposition modulation of ZnOHF precursors. The optimized NO 2 sensor demonstrates unparalleled humidity-independence across a wide operating temperature range with prime sensitivity, low detection limit and rapid response/recovery. Matrix algorithm is also implemented in highly precise NO 2 identification under complicated atmospheric and humid conditions. Mechanism studies based on temperature programmed desorption (TPD), quasi in-situ X-ray photoelectron spectroscopy ( Quasi in-situ XPS) reveal that F − dopants facilitate interfacial electron transferring and inhibit oxygen activity. In-situ diffuse reflectance infrared Fourier transform spectroscopy ( In-situ DRIFTS) demonstrates that hygroscopic NiO and electronegative F − synergistically obstruct hydroxyl adsorptions on sensing materials. The innovative approach offers a promising solution for enhancing moisture resistance of MOS sensors for real-time NO 2 concentration monitoring in fuel cells and provides valuable insights into anti-humidity mechanisms.