A Study Of Preparation And Properties Of The Iodine-Modified Molybdic Acid

MoO₃, as one of transition metal oxides, was applied in many fields, such as gas sensing, catalyst, smoke suppression filling, etc. Because of its unique layer structure, different guest molecules or cations, such as alkali metal ions and organic molecules, can be interclated into the MoO₃ interlayer or crystal lattice and form molybdenum bronze. These compounds, or molybdenum bronzes, are interest in many fields because of their novel properties and potential applications in battery, solar transform devices and so on. In fact, it needs a long time to apply them in our lives because it is difficult to prepare the molybdenum bronzes, and their functional properties also need to be enhanced. Therefore, it is necessary to do further research on molybdenum bronzes.In this paper, we prepared the molybdenum trioxide and molybdic acid by the reaction of (NH4)6Mo7O24·4H2O with HNO₃, and characterized by XRD, SEM. The influences of the concentration of the ammonium molybdate, pH, titration velocity of nitric acid, dehydration temperature and surfactant on the structure and size of the molybdic acid were discussed. The results indicate that the crystal structure of as-prepared molybdic acid is influenced by the dehydration temperature, pH, and surfactant, and the particle size is influenced by the concentration of ammonium molybdate and titration velocity.The iodine-modified green molybdic acid was prepared by electric field polarization of as-prepared molybdic acid in iodine mixture solution. The XPS indicate that iodine ions exist in the green molybdic acid. UV-Vis-FTIR spectra indicate the green molybdic acid shows an extinctive absorption band in 460⁷90 nm with the maximum absorption wavelength at 620 nm.The photochromism of the iodine-modified molybdic acid was studied in this paper. The results indicate the iodine-modified green molybdenum bronzes can be improved by UV lamp irradiation. Furthermore, the gas sensitivity of the iodine-modified molybdic acid to NH₃, CH₃CH₂OH, C₃H₆O, O₃ was also investigated at room temperature, and the sensitivity, selectivity and response-reversion time were also discussed. The results indicate that the iodine-modified molybdic acid shows sensitivity to NH₃ at room temperature. Therefore, the molybdenum bronzes prepared of the I-modified molybdic acid can be used as potential materials in photochromic device and gas sensor to NH3 at room temperature.