In2O3 and Pt-In2O3 nanopowders for low temperature oxygen sensors

In2O3 and Pt-doped In2O3 nanopowders were investigated for oxygen monitoring at low temperature (from RT to 350 °C). In the first step, In2O3 nano-sized powders were synthesized by a non-aqueous sol-gel method, followed by deposition of 1 or 3 wt% Pt on the surface of the semiconducting metal oxide by wetness impregnation. In comparison to undoped In2O3, the Pt-doped sensors showed better performances in terms of sensitivity, response and recovery times, presumably due to the increased number of active sites for oxygen adsorption and dissociation, which favours the exchange kinetics of gaseous oxygen with adsorbed oxygen species. Depending on the working temperature, surface and/or bulk effects contribute to the oxygen sensing mechanism, strongly influencing the response and recovery times, as well as, the shape of the transient response. The high response combined with fast response and recovery times makes the Pt-In2O3 sensors a promising candidate for applications in oxygen monitoring at low temperature.