Construction of hollow NiO/ZnO p-n heterostructure for ultrahigh performance toluene gas sensor

In this work, NiO/ZnO hollow microspheres were successfully fabricated by a simple co-precipitation method. The structural and morphological properties of NiO/ZnO composites were studied by various characterization methods. Gas sensing results revealed that the sensor of NZ-2 and the working temperature was 300 °C showed highest response value (S = 240) and good selectivity to 100 ppm toluene. Compared with pure ZnO hollow microspheres, the sensitivity of NiO/ZnO hollow microspheres is significantly improved by about 20 times. The response/recovery time were 2/33 s respectively at the same time, the detection limit can be reduced to ppb level. The possible mechanism for improvement of gas sensing performance is detailly analyzed, which is mainly due to the unique hierarchical microstructure and the composition of p-n heterojunction at the contact surface between p-type NiO and n-type ZnO structures as well as the catalytic effect of NiO.