The Effect of Noble Metals on Co Gas Sensing Properties of In2O3 Nanoparticles

Three types of In2O3 nanoparticles decorated with Au, Pd and Pt nanoparticles, respectively, were synthesized by thermal decomposition method, and the effects of metal nanoparticles on their phase, microstructure, chemical state, carrier types were investigated with XRD, SEM/TEM, and XPS. Additionally, sensing properties to CO gas, such as sensitivity, etc., were examined with sensing apparatus. Au-decorated In2O3 nanoparticles exhibited the highest sensitivity to CO gas, with S = 5.59 at a 10 ppm CO gas concentration at 50 °C compared to Pd or Pt-decorated In2O3 nanoparticles. This can be interpreted as a much higher adsorption of oxygen molecules on the In2O3 surface due to the high oxygen vacancies in the In2O3 lattice, which generates an electron depletion region in the outer layer of In2O3 to sharply increase the resistance or the spill-over effect due to Au nanoparticles on In2O3. Au nanoparticles were observed in the TEM images and confirmed by XPS analysis.