Highly sensitive and selective ethanol sensors using magnesium doped indium oxide hollow spheres

Abstract

Pure In2O3, 0.5 and 1.0 wt% Mg doped In2O3 hollow spheres were synthesized by ultrasonic spray pyrolysis of a solution containing In-, Mg-nitrate and sucrose and their gas sensing characteristics to 5 ppm C2H5OH, p-xylene, toluene, and HCHO were measured at 250, 300 and 350oC. Although the addition of Mg decreases the specific surface area and the volume of meso-pores, the gas response (resistance ratio) of the 0.5 wt% Mg doped In2O3 hollow spheres to 5 ppm C2H5OH at 350oC (69.4) was significantly higher than that of the pure In2O3 hollow spheres (24.4). In addition, the Mg doped In2O3 hollow spheres showed the highest selectivity to C2H5OH. This was attributed to the dehydrogenation of C2H5OH assisted by basic MgO into reactive CH3CHO and H2.