Characterization
Chemical analyses of each aged adsorbents were performed by various analytical techniques to determine the physical and chemical changes of Ag0Z after being aged. Scanning Electron Microscopy (SEM, JEOL 5600) was employed to observe surface structure change on aged samples by obtaining information on each sample’s surface and chemical composition.
X-ray diffraction (XRD, Bruker D8 Advance ECO powder diffractometer) equipped with a Cu Kα radiation (λ=1.540456 Å) at 40 kV and 25 mA was employed to observe the impacts of aging gases on Ag0to describe behavior of silver particles. Diffraction patterns were collected at the 2θ-range between 15° and 60°, and the results were analyzed with the software MDI Jade version 9.0.
X-ray Photoelectron Spectroscopy (XPS, Surface Science Instruments SSX-100) in an ultrahigh vacuum was employed for surface elemental analysis to investigate the change of oxidation state of Ag in the adsorbents when exposed to the studied gas streams. A monochromatic Mg Kα X-ray source (1486.6 eV) at a working pressure in the analyzing chamber of ~2 × 10-9 Torr was used to obtain the spectra. Survey/wide scans were performed using a pass energy of 150 V, and high-resolution scans were conducted with a pass energy of 50 V. A flood gun was used for charge neutralization. The binding energy (BE) of core-level Ag 3d was measured. C 1s peak at 284.2 ± 0.1 eV BE was taken as internal reference. Analysis of the data was performed with the Casa XPS program (Casa Software Ltd., UK).