Abstract
Thick film polycrystalline 
gas sensors for hydrogen partial pressure determination in hydrogen‐air mixtures present a very complex kinetic behavior that demands to be thoroughly clarified in order for them to be used in practical applications. For this reason a systematic investigation has been carried out on the time and temperature dependence of the electrical conductivity of 
films deposited via spray pyrolysis on ceramic substrates in the temperature range 498‐573 K in the presence of dispersed Pt as the catalyst. Results of this investigation show that the hydrogen‐assisted reaction of desorption of surface chemisorbed oxygen occurs in parallel with a reaction of direct 
reduction in the whole range of temperatures investigated. When accounting for this parasitic reaction, a good fit of the 
partial pressure and time dependence of the electrical conductivity with the theoretical predictions has been observed by assuming a conductivity dominated by Schottky barriers at grain boundaries.