Ultra-sensitive H2 sensors based on flame-spray-made Pd-loaded SnO2 sensing films

In this paper, ultra-sensitive hydrogen (H-2) gas sensors based on flame-spray-made Pd-catalyzed SnO2 nanoparticles is presented. Pd-loaded SnO2 crystalline nanoparticles with high specific surface area and well-controlled size were synthesized by flame spray pyrolysis (FSP) in one step. The particle properties were characterized by XRD, BET, SEM, TEM and EDS analyses. The H-2-sensing performances in terms of sensor response, response time and selectivity were optimized by varying Pd concentration between 0.2 and 2 wt%. An optimal Pd concentration for H-2 sensing was found to be 0.2 wt%. The optimal sensing film (0.2 wt% Pd/SnO2, 10 mu m in thickness) showed an ultra-high sensor response of similar to 10(4) to 1 vol% of H-2 at 200 degrees C and very short response time within a few seconds. Moreover, the optimum sensing temperature of Pd-loaded SnO2 films was shifted to a lower value compared with that of unloaded SnO2 film. The significant enhancement of H-2 sensing performances was attributed to highly effective spillover mechanism of well-dispersed Pd catalyst in SnO2 matrix at low Pd-loading concentration. Furthermore, the catalyst selectivity of Pd toward H-2 was found to be significantly higher than those of two other noble metals including Pt and Ru, respectively. Therefore, the flame-made 0.2 wt% Pd/SnO2 sensors is one of the most promising candidates for highly sensitive and selective detection of H-2. (C) 2012 Elsevier B.V. All rights reserved.