H2 gas sensor based on PdOx-doped In2O3 nanoparticles synthesized by flame spray pyrolysis

In this work, 0-1.0 wt% PdOx-doped In2O3 nanoparticles were successfully synthesized by flame spray pyrolysis (FSP) in a single step for the first time and investigated for gas-sensing applications. The sensing films were fabricated by spin coating and tested towards hydrogen (H-2) at various temperatures ranging from 150 to 350 degrees C in dry air. The powder and sensing film properties were analyzed by X-ray analyses, nitrogen adsorption and electron microscopy. The spherical and cubic In2O3 nanoparticles with diameters ranging from 2 to 20 nm were observed with no apparent secondary phase of Pd or PdOx. Detailed analyses suggested that Pd species might be in the form of PdOx crystallites embedded in and on grain boundaries of In2O3 nanoparticles. From gas-sensing measurements, hydrogen-sensing characteristics of In2O3 nanoparticles were significantly improved by PdOx doping particularly at the optimal Pd content of 0.50 wt%. The optimal PdOx-doped In2O3 sensing film showed a high response of 3526 towards 10,000 ppm H-2 at the optimal working temperature of 250 degrees C. In addition, PdOx doped In2O3 sensing films displayed good stability and high H-2 selectivity against various toxic and flammable gases including H2S, NO2, C2H4O, C2H4, C2H5 OH and C2H2.