Core-shell NiO Sphere Prepared by a Facile Method with Enhanced VOC Gas Sensing

In this work, we reported a novel core–shell NiO spheres with a three-layer structure for gas sensor. The obtained gas sensors exhibited a higher response, rapid response/recovery rate and nice reproducibility. The gas sensitivity test results showed that NiO-12 h with a three-layer structure obtained a gas response of 35.4, a response/recovery time of 13/9.8 s, to 200 ppm ethanol at 350 °C. The enhancement of gas sensing performance gave credit to the special core–shell structure and the more O V and O C . Furthermore, the formation mechanism of the core–shell structure was analyzed and we found that the formation of the core–shell structure was closely related to the reaction time. This work not only gave a solution for improving the gas sensing performance of the gas sensors based on NiO, but provided an analysis of the growth mechanism of the core–shell structure.