Sc-doped NiO nanoflowers sensor with rich oxygen vacancy defects for enhancing VOCs sensing performances

Highlights:• Sc-doped NiO nanoflowers have been synthesized via a facile wet chemical method.• Sc aliovalent dopant could substantially boost the responses of p-type NiO sensor toward VOC molecules.• Other than Ni³⁺, surface unsaturated oxygen vacancy defects play an important role in facilitating VOC/NiO interfacial charge exchange. -- Abstract: Identifying the defect type which closely correlates with gas/metal oxide semiconductor (MOS) interfacial charge exchange is of utmost importance for rationally designing high performance MOS gas sensors, which are essential for the emerging sensing electronics for assessing the personal health and environment pollution. Herein, we report the sensing performance of p-type NiO toward volatile organic compounds (VOCs) molecules could be drastically improved by Sc dopant. At an optimal doping ratio of 7.4 at.%, the sensor response to 100 ppm acetone was boosted from 8.2 (pure NiO) to 109.4, with a low detection limit of 10 ppb. Comprehensive defect characterizations indicate surface unsaturated oxygen vacancy (V_O) defects act as active sites that facilitate the interfacial charge exchange at elevated temperatures. Our work highlights that abundant V_O defects induced by aliovalent Sc dopant play an important role in boosting the sensitivity of p-type NiO toward VOCs, and provide valuable guidance in designing high performance p-type MOS sensors.