Improvement of sensing properties for SnO2 gas sensor by tuning of exposed crystal face

Abstract

In this study, a SnO2 nanosheet was successfully synthesized under moderate conditions without using any additive. The crystal growth direction and the mainly exposed crystal face of the SnO2 nanosheet were investigated. The relationship between the exposed crystal face and the gas sensing properties was also investigated. It was confirmed that the SnO2 nanosheet has a plain size of ˜100 nm and a mainly exposed (101) plane. The SnO2 nanosheet exhibited selectively higher sensor signal response for H2 than CH4 gas, while the SnO2 nanoparticle with a mainly exposed the most stable (110) plane, which was prepared for comparison purposes, exhibited a selectively lower sensor signal response for H2 than CH4 gas. The 90% response and recovery times for the SnO2 nanosheet were faster than those for the SnO2 nanoparticle for both H2 and CH4 gases. Different chemical states were observed on the SnO2 surfaces. Therefore, it was considered that the reaction with the target gas on the SnO2 nanoparticle was dominantly induced by oxygen adsorbed on the SnO2 surface. However, the reaction was dominantly induced by oxygen bound to Sn on the SnO2 nanosheet, due to the ease of conversion of the Sn valency state according to adsorption and desorption of oxygen on the (101) surface as compared to the (110) surface.