Detection of ppm-level H2 via rGO-SnO2-ZnO nanocomposites: Considering compositional matching in designing heterostructured gas-sensing materials

Synergistic effects have been utilized to explain the sensing mechanism of heterostructured gas sensing materials. However, it is challenging to clarify the precise contribution of the heterojunction, making it difficult to apply findings generally to all sensing materials. In this work, heterostructured rGO-SnO2-ZnO nanocomposites were produced by dispersing ZnO on rGO-SnO2 and their H2 sensing properties were investigated. The morphology of ZnO changed from the form of nanoparticles in 5% rGO-SnO2-ZnO nanocomposites to the form of nanowires in 10% rGO-SnO2-ZnO nanocomposites, and the corresponding maximum sensor responses to 500 ppm H2 at 175 °C increased from 15.6 to 18.0. Further increasing the content of ZnO nanowires significantly deteriorated the sensing performance of the final nanocomposites. It is confirmed that heterojunction modulation is the dominant sensitization mechanism of the rGO-SnO2-ZnO nanocomposites and it is crucial to ensure the backbone sensing material maintains its electrical conductivity and avoid any shielding effect from the decorated component in designing heterostructured gas sensing materials.