Density functional theory study on a new gas sensing material: Pd-doped PC6

Abstract:

The absorption properties of Pd-doped PC6 (PdPC6) for the individual O2, CO, NO, N2O, NO2, SO2, H2S and NH3 molecules are studied by using the first-principles calculation method based on density functional theory, and the influence of gas molecule adsorption on the electronic and optical properties of PdPC6 is analyzed. The results show that Pd doping in PC6 enhances the adsorption energy of gas molecules and shows the adsorption sensitivity to the eight gas molecules. The adsorption of gas molecules causes the reconfiguration of the charge distribution of the system and hence the change of its electronic properties. PdPC6 transforms from metal to semiconductor after O2, NO, NO2 and SO2 adsorptions, while it retains metal property after the adsorptions of CO, N2O, H2S and NH3. The adsorptions of O2, CO, NO and SO2 can induce PdPC6 to produce magnetism and exhibit different spin distribution characteristics. The adsorption of gas molecules can also adjust PdPC6’s work function, and its value depends on the quantity and orientation of charge transfer. Gas adsorption can result in variation of optical absorption spectra of PdPC6. O2, NO, NO2 adsorptions make the system produce new absorption peaks at different frequencies in the low frequency region, therefore, the species of gas molecules can be identified by measuring the absorption spectrum at a specific frequency. The results provide a basis for the design and preparation of gas sensors with high sensitivity and high selectivity.