Gas sensing properties of catalytically modified WO3 with copper and vanadium for NH3 detection

Ammonia gas detection by pure and catalytically modified WO₃ based gas sensor was analysed. The sensor response of pure WO₃ to NH₃ was not only rather low but also presented an abnormal behaviour, probably due to the unselective oxidation of ammonia to NO_x. Copper and vanadium were introduced in different concentrations and the resulting material was annealed at different temperatures in order to improve the sensing properties for NH₃ detection. The introduction of copper and vanadium as catalytic additives improved the response to NH₃ and also eliminated the abnormal behaviour. Possible mechanisms of NH₃ reaction over these materials are discussed. Sensor responses to other gases like NO₂ or CO and the interference of humidity on ammonia detection were also analysed so as to choose the best sensing element.