Gas Sensing Properties Of In₂O₃ NW-like Network Synthesized By CNTs Templates

The purpose of the present work is to enhance the sensitivity and shorten response/recovery time. A novel approach was designed to synthesize Pd-loaded In2O3 NW-like network via electroless plating using MWCNTs as templates in combination with oxidization and subsequent calcination. Pd-loaded In2O3 NW-like network sensor presented excellent gas sensing property to NO2 because of their higher surface-to-volume ratios. In addition, the loaded Pd dramatically improved the response and response/recovery time. The morphologies and structures of samples were investigated; meanwhile formation mechanism and presentation parameters were studied through TEM. The sensor testing system was used to measure various In2O3. The effects of specific area and the mechanism were explained. And spillover effect was introduced to explain the response curve.CNTs were treated by the two steps to obtain Pd-modified CNTs. Then indium deposited onto the surface of the CNTs. Finally, Pd-In2O3 NW-like network structures were obtained by oxidation and calcination. Oxidation time plays an important role for the morphology of the Pd-In2O3. The grain size of In2O3 is decreasing with the increasing of oxidation time. When oxidation time reaches 60 h Pd-In2O3 presents nanowire-like network. The porous unloaded In2O3 were obtained by electroless using CNTs as templates and followed by 60 h oxidation and 550 °C calcination in the absence of PdCl2, but keeping other condition unchangedThe gas sensing measurements revealed that the optimum temperature of three sensors is 110 °C, and loading Pd is an effective approach to shorten the response and recovery times. Besides, two novel characteristics, ―pulse signal‖ and ―cyclical fluctuations‖ appeared. And another result was obtained the response of Pd-loaded In2O3 NW-like network was 27, which was about 5 times larger than that of porous Pd-In2O3(about 5.5) when exposed at concentration as low as 5 ppm at 110 °C due to larger surface to volume ratio. In addition, the two sensors(porous Pd-In2O3 and unloaded In2O3) with the similar morphology but different components have more or less the same response value due to different effects.