High energy facets and oxygen vacancies guided hierarchical tin dioxide microcubes assembled by cross-stacked nanoslices for ethanol gas-sensing

For metal oxide gas sensors, the upstream theoretical mechanism can provide both quantum guidance for screening favorable materials and important insights in fabricating electronic devices. However, except for widely popular Yamazoe's 'receptor-transducer-utility' model, some specific theoretical models still lack for diverse sensing properties of metal oxide semiconductor currently. Based on a deeper understanding of surface catalytic mechanism, n-type SnO2 was selected as an example to screen a better solution. Herein, hierarchical SnO2 microcubes assembled from cross-stacked nanoslices were synthesized via a self-templated method, and the SnO2 microcubes displayed versatile performances with excellent response to 100 ppm ethanol (Sr = Rair/Rgas = 56.9), relative low optimal working temperature of 170 °C, good repeatability under high R.H. (90%) and ultra-low detection limit even under 0.1 ppm. The performances of SnO2 nanofilms, hierarchical SnO2 nanotubes and commercial SnO2 powder were also studied. The results showed that the increase of exposed higher energy facet of (101) and rich oxygen vacancies on 3D-crossed nanoslices of SnO2 microcubes contribute to outstanding gas sensing performances, which were also confirmed by the DFT calculations. These demonstrate a diverse sensing mechanism and a new insights for state-in-art gas sensing materials of SnO2.