Correlation between methylmercaptan gas-sensing properties and its surface chemistry of SnO2-based sensor materials

Methylmercaptan gas-sensing properties of SnO2-based sensors have been investigated in the temperature range of 200–600°C. Further efforts have been directed to clarifying the reaction kinetics of CH3SH by investigating its oxidation behavior over pure SnO2 as well as desorption behavior of reaction products from the CH3SH-preadsorbed pure SnO2. A pure SnO2 sensor exhibited a relatively high CH3SH sensitivity of about 8000 at 250°C. Among the SnO2-based sensors tested, only the SnO2 loaded with 0.5 wt.% Pt exhibited slightly improved sensitivity. It was revealed that CH3SH, CH3SSCH3, CH3SCH3, HCHO and SO2 were adsorbed on the SnO2 surface at 250°C during the sensitivity measurement. Although CH3SH, CH3SCH3 and HCHO were suggested to be positively chemisorbed, it was confirmed that the large CH3SH sensitivity at 250°C arose mainly from the consumption of oxygen adsorbates during the reaction with CH3SH.