Subtle interaction between Ag and O 2 : a near ambient pressure UV photoelectron spectroscopy (NAP-UPS) investigations
| Title | Subtle interaction between Ag and O 2 : a near ambient pressure UV photoelectron spectroscopy (NAP-UPS) investigations |
| Publication Type | Journal Article |
| Year of Publication | 2018 |
| Authors | Ghosalya, MKumar |
| Secondary Authors | Reddy, KPrabhakar |
| Tertiary Authors | Jain, R |
| Subsidiary Authors | Roy, K, Gopinath, CS |
| Journal | Journal of Chemical Sciences |
| Volume | 130 |
| Issue | 3 |
| Pagination | 30 |
| Date Published | MAR |
| Type of Article | Journal Article |
| ISSN | 9743626 |
| Keywords | Electronic Structure, epoxidation, heterogeneous catalysis, Surface Science |
| Abstract | The Ag-O2 interaction, which is at the center-stage of Ag-catalyzed partial oxidation reactions, is studied with NAP-UPS up to 0.2 mbar O2 pressure between 295 and 550 K. Three temperature regimes were identified for distinct Ag-O2 interaction, which are (a) 295–390 K, where mainly dissociative chemisorption of O2 happens, (b) 390–450 K, where diffusion of O-atoms into the sub-surfaces of Ag is prominent, and (c) >450 K, where metastable oxide forms on polycrystalline Ag surfaces. The work function (WF) of Ag changed from 4.95 (≤390 K) to 5.30 eV (390–450 K), and then to 5.7 eV (≥450 K) at 0.1 mbar O2 pressure. Oxygen population in the sub-surfaces imparts crucial modifications to Ag at 390–450 K; it makes the surface to be electron-deficient that relates to the change in the WF of Ag and facilitates the formation of space charge layer on Ag surface. Oxygen adsorbed on such modified Ag-surfaces is electrophilic in nature, and this appears at a higher binding energy in core level XPS than the chemisorbed oxygen on metallic Ag. This is supported by angle-dependent NAP-XPS studies. The subsurface population of oxygen in Ag no longer persists at >410 K when the O2 supply is removed. A high ratio of antibonding/bonding O 2p bands suggests the unique silver-oxygen interaction under the measurement conditions. |
| DOI | 10.1007/s12039-018-1434-3 |
| Type of Journal (Indian or Foreign) | Foreign |
| Impact Factor (IF) | 1.235 |
Divison category:
Catalysis and Inorganic Chemistry
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