Fabrication Of Palladium Oxide Based Sensitive Material And Study Of Their Gas Sensing Properties At Room Temperature

Metal oxide semiconductors are the most widely used kind of sensing materials among resistance type gas sensor, most of which need a 150?400? working temperature while testing pollution and flammable gases. A high operating temperature would bring lots of disadvantages in working power, stability, security, and so on. In recent years, as a narrow-band-gap p-type semiconductor oxide, the gas sensing properties'of palladium oxide have begun to be focused. In this paper, PdO nano-materials are treated as the main gas sensing materials and prepared by different methods, and the gas sensing properties at room temperature are tested. The main contents are as follows:Precipitation method was used in the preparation of PdO materials, which were stacked by nano-particles with about 10nm diameter. TGA, XRD, and SEM were used to characterize. The sensing properties of PdO materials, which were calcined under different temperatures, to CO at room temperature were tested using the dynamic gas distribution system. The result showed that 700? was the optimum calcination temperature. PdO materials exposed in different conditions for long-term treatment were characterized by XPS, and the type of oxygen involved in the oxidation of CO in PdO materials were analyzed. The gas sensing mechanism of PdO was studied by testing the response and recover properties of PdO to O2 under different working temperature and to CO without O2 in background atmosphere.PdO materials were prepared by hydrothermal method with CTAB as dispersant, and the morphology and structure were characterized. The formaldehyde sensing properties at room temperature were tested using a static gas distribution system. The result showed that when n(PdCl2):n(CTAB)=1:3, the gas sensing properties were much better. Then the sensing mechanism was explained, and a comparison between PdO prepared by precipitation and hydrothermal was made. It is showed that the long-term stability and repeatability of PdO materials prepared by hydrothermal were much better than by precipitation.PdO/CuO composite nano-materials with different atomic ratios of palladium and copper were prepared through hydrothermal method, and XRD, XPS, SEM were used to characterize the composite materials. The sensing properties to formaldehyde at room temperature were tested. And when the atomic ratio of Pd and Cu was 1:2, the composite materials had the highest response. It is showed that there was an obvious improvement in the response of PdO after compound with CuO. By analyzing the microstructure and heterostructure of materials, the mechanism of the improvement of response in composite nano-materials was discussed.