Comparison of single and binary oxide MoO3, TiO2 and WO3 sol–gel gas sensors

A systematic comparison of sol–gel prepared titanium dioxide (TiO2), WO3, and MoO3 single metal oxide based gas sensors was conducted. Process variables such as solution concentration, deposition parameters, gelling time, annealing time and temperature, remained constant. Sensors based on binary compound MoO3–TiO2 and MoO3–WO3 were also investigated to determine if the performance is superior to their single oxide constituents. The sensors were systematically exposed to O2, O3, CO and NO2 gases and ethanol vapor at concentration levels of particular interest. MoO3 binary compound based sensors showed promising O3, CO and NO2 gas response. Their use as a sensing film for gas is limited due to the materials low evaporating temperature, limiting its operating temperature below 350 °C. However, the binary oxide of MoO3–WO3 showed a high response to ethanol vapor and a highly selective response to NO2.