Figure 11. The regional scans of Ag(a), I(b) and the curve fits of the 104 ppbv/ 200 ℃ CH3I adsorbed Ag0-Aerogel.
Reported in multiple studies,43-47 the Ag BE tends to decrease as the oxidation state increases. For example, the Ag3d5/2 BE of metallic Ag is approximately 368.1, and this value decreases to 367.7-367.9 eV for Ag+ and 367.3-367.6 eV for Ag2+. Admittedly, the instrument deviations and data calibration standards may vary the BE measured, but the trend indicates that a certain amount of Ag2+ may be formed in 104 ppbv CH3I adsorption at 200 ℃, whereas the peak group 3 remains questionable.
The Ag and I concentrations can be interpreted from the XPS and SEM-EDX spectra, where the results are listed in Table 3. To compare the iodine concentrations between samples, the iodine compositions have been calibrated as additional mass, which the summations of all other elements are 100%. It is important to noticed that the Ag0-Aerogel is a highly heterogeneous material; the Ag coverage on the pellets is uneven, and the values measured by SEM-EDX and XPS may vary based on the specific location scanned.