Detection of propane by “GaON” thick-film gas sensors

The detection mechanism of propane by gallium oxynitride (“GaON”) sensors was investigated. The electrical resistance of the sensors was monitored during propane exposure (0, 15, 30, 50 and 100 ppm) in dry and humid atmosphere (10% relative humidity at room temperature), at different oxygen concentrations (0, 2, 5, 10 and 20%). Temperature programmed desorption-mass spectrometry (TPD-MS) was used to investigate the species desorbing from the surface of “GaON” after exposure to propane at 250 °C and 350 °C. The detected species were propene, propane, CO, CO2, NH3 and H2O. This study demonstrates that the oxidative dehydrogenation (ODH) of propane on “GaON” can take place without oxygen in the gaseous phase, thus implying a redox Mars–van Krevelen mechanism, which involves the contribution of lattice oxygen and possibly nitrogen during the activation of propane on the sensor surface.