Oxygen vacancy engineering via Mo doping in NiO nanofibers for selective trace xylene detection

Abstract

Xylene poses a threat to environmental and public health due to its neurotoxicity and strong irritancy, necessitating the development of efficient trace detection technologies. However, existing metal oxide semiconductor-based xylene sensors tend to have drawbacks such as high detection limits, insufficient response, poor humidity resistance, and susceptibility to cross-interference from aromatic compounds. In this study, Mo-doped nickel oxide nanofibers with varying doping ratios were fabricated by combining a facile electrospinning process with thermal treatment, and their gas-sensing properties were systematically evaluated. The results demonstrate that the sensor with a Mo doping concentration of 12.5 at% exhibited the maximum response to 20 ppm xylene at 265 °C (S ≈ 120.9), an ultra-low detection limit of 20 ppb, excellent selectivity, outstanding humidity resistance, and long-term stability. The improvement in sensing performance primarily stems from the modulation of valence state distribution in nickel oxide by aliovalent molybdenum doping. This process improves charge transfer efficiency and increases oxygen vacancy concentration. Additionally, the incorporation of Mo significantly enlarges the specific surface area and increases the quantity of micropores and mesopores. These factors collectively optimize the activity of surface chemisorbed oxygen, thereby markedly improving gas-sensing reaction efficiency. In situ Fourier transform infrared analysis reveals the surface oxidation reaction process and final reaction products of xylene. This work provides a feasible material strategy for developing high-performance xylene gas sensors, demonstrating promising potential for applications in trace xylene detection.