Comparative study on the gas-sensing performance of ZnO/SnO2 external and ZnO–SnO2 internal heterojunctions for ppb H2S and NO2 gases detection

Abstract

• ZnO-SnO 2 composite NFs and ZnO/SnO 2 hetero-NFs were synthesized by electrospinning. • Gas sensing characteristics of fabricated NFs were studied to H 2 S and NO 2 gases. • Internal-junction and external-junction can result in a high response of NF sensors. • The high response of NF sensors was governed by internal-junction. The design of hetero-nanojunctions can greatly amplify the gas-sensing performance of conventional metal oxide gas sensors. In this study, the composite nanofibers (NFs) of ZnO–SnO 2 internal heterojunctions (HJs) and the mixed NFs of ZnO/SnO 2 external HJs were realized by using the electrospinning technique. Then, the gas-sensing characteristics of the as-synthesized NFs toward H 2 S and NO 2 gases were systematically investigated and compared. The effects of the internal and external nanojunctions of the hetero-NF-based gas sensors were also explored. Results showed that the ZnO–SnO 2 composite NFs demonstrate a higher response than those of the ZnO/SnO 2 mixed NFs, as well as bare ZnO and SnO 2 NFs. Also, the cross responses of the hetero-NF sensors toward 200 ppm CO, 250 ppm H 2 , and 250 ppm NH 3 were examined. The gas-sensing mechanism of the internal and external HJs of composite ZnO/SnO 2 and mixed ZnO/SnO 2 NFs was analyzed. The remarkable enhanced gas-sensing performance of hetero-NFs was mainly attributed to the formation of internal HJs.