Abstract
The adsorption phenomena taking place on the powdered solid surfaces have been elucidated by the measurement of heat of adsorption and the spectroscopic observation. As to the interaction between the metal-oxide surface and water molecules, metal oxides exhibit either an energetically homogeneous nature or heterogeneous nature; ZnO, Cr2O3, and SnO2 belong to the former type, and TiO2, ZrO2, Al2O3, and SiO2 to the latter type. Two-dimensional condensation of water occurs on the hydroxylated surfaces of ZnO, Cr2O3, and SrF2, which is due to the strong and lateral interaction of water molecules adsorbed on the homogeneous solid surface. In this review the peculiar adsorption found in the zeolite-dinitrogen system is also described and the process of investigating its mechanism is introduced by showing the data of adsorption heat and spectroscopic observation such as IR, XAFS (including EXAFS and XANES), and emission spectra. The copper ion species ion-exchanged in mordenite or CuZSM-5-type zeolite act as effective sites for dinitrogen adsorption at room temperature. The monovalent copper ion species (Cu+) that produced by the heat treatment at high temperature in vacuo is responsible for the strong adsorption of dinitrogen. Usefulness of combining the adsorption calorimetry and spectroscopic observation is also described in this review.
