In2O3 is introduced into TiO2 by sol-gel method to improve the response/recovery rate and expand the operating temperature, when the In2O3-TiO2 mixed system is exposed to H-2/O-2. The sensor is fabricated by thick film technology. Influence of In2O3 on the film phase composition, microstructure and sensing characteristics is discussed. Dynamic response properties show that the operating temperature of the mixed system is at 500-800 degrees C, which is about 600-800 degrees C for pure TiO2. Response time of the sensor is about 200-260 ms (millisecond) while recovery time is in a narrow range of 60-280 ms at 600-800 degrees C. The promoting mechanism is suggested to arise from the introduction of In2O3 and grain size effect of the sensing film. Then In2O3-TiO2 thick films are surface-modified by Pt using chloroplatinic acid. The promoting effect of Pt dispersed on the mixed system is also investigated. (C) 2011 Elsevier B. V. All rights reserved.