Highly sensitive NO2 gas sensor based on ZnO nanoarray modulated by oxygen vacancy with Ce doping

Abstract

Developments of advanced sensors for NO2 gas with high sensitivity and selectivity are essential but challenging. In this work, a Ce-doped ZnO nanoarray (termed as CZO) was successfully constructed via a one-pot hydrothermal method, and further demonstrated as a promising NO2 chemiresistive sensing material. It proves that Ce doping not only changes the morphology of the initial ZnO nanoarray, but brings abundant oxygen vacancy in particular, as comprehensively proofed by scanning electron microscopy, transmission electron microscopy, and electron spin resonance spectroscopy. Gas sensing tests at 250 °C reveal that CZO-2 (Ce wt% = 2 %) offers a 10-fold higher sensing response to NO2 and much lower limit of detection (LOD = 1.4 ppb), compared to those of the initial ZnO nanoarray. Additionally, high selectivity for NO2 and excellent long-term stability are also obtained in such a Ce-doped sensor. Density function theory calculation results show that ZnO modulated by oxygen vacancy has a much stronger affinity toward NO2 than pure ZnO, thus resulting in the improved sensing performance observed in CZO-2.