Modulation of potential barrier heights in Co3O4/SnO2 heterojunctions for highly H2-selective sensors

Chemiresistive gas sensors employing p-n heterostructures offer a compelling combination of high sensitivity and specific selectivity due to the synergic effects at interface. In this study, the p-Co3O4/n-SnO2 composites with different molar ratio of Co/Sn have been prepared using a simple soak-calcination method and their sensing properties are systematically investigated. The sensors demonstrate exclusive H-2 sensing properties with p-type sensing response, and n-type sensing response to the typical reducing gases such as CO, H2S and NH3. We propose that the abnormal sensing behaviors might be associated with the modulation of potential barrier heights formed in p-Co3O4/n-SnO2 heterojunctions, namely the modulation from the asymmetric gas sensing reactivity of SnO2 and Co3O4 to the reducing gases. This work may open up a general approach for tailoring the sensing selectivity of gas sensors via the modulation of potential barrier heights in p-n heterojunctions. (C) 2017 Elsevier B.V. All rights reserved.