Reaction of SO{sub 2} with cesium and cesium-promoted ZnO and MoO{sub 2}

Journal Article · Thu Mar 18 04:00:00 EST 1999 · Journal of Physical Chemistry B: Materials, Surfaces, Interfaces, amp Biophysical

DOI:https://doi.org/10.1021/jp984318d· OSTI ID:335238

Rodriguez, J A; Jirsak, T; Hrbek, J ^[1]

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1. Brookhaven National Lab., Upton, NY (United States). Dept. of Chemistry

The chemistry of SO{sub 2} on pure metallic Cs and Cs-promoted polycrystalline surfaces of ZnO and MoO{sub 2} has been studied using high-resolution synchrotron-based photoemission. Metallic cesium reacts vigorously with SO{sub 2} at temperatures between 100 and 300 K. At 100 K, the amount of SO{sub 2} that fully dissociates (SO{sub 2,gas} {r_arrow} S{sub a} + 2O{sub a}) on the alkali metal is relatively small, and SO{sub x} (x = 2--4) species predominate on the surface. SO{sub 3} and SO{sub 4} may be formed as a result of the reaction of SO{sub 2} with atomic oxygen (SO{sub 2} + nO{sub a} {r_arrow} SO{sub 2+n,a} where n = 1--2), or by disproportionation of chemisorbed SO{sub 2}. At 300 K the stability of the CsSO{sub x} species is lower than at 100 K, and the formation of CsO{sub y} and CsS{sub y} becomes important. In the Cs/ZnO and Cs/MoO{sub 2} systems, the alkali {leftrightarrow} oxide interactions are very strong. Despite this, the supported Cs atoms retain a large chemical affinity for SO{sub 2} and are able to enhance the rate of adsorption of the molecule on the oxide surfaces, even at low coverages (0.1--0.2 ML) of cesium when the alkali atoms are in a highly ionic state (Cs{sup {delta}+}). The larger the coverage of Cs on ZnO and MoO{sub 2}, the faster the rate of adsorption of SO{sub 2}, and the larger the amount of S and SO{sub x} (x = 2--4) species present on the surface. The adsorption of SO{sub 2} on ZnO and Cs/ZnO surfaces was examined using ab initio self-consistent-field (SCF) calculations and cluster models. The Cs adatoms provide occupied states that are very efficient for bonding interactions with the LUMO of SO{sub 2}. Cs atoms supported on Zn-terminated terraces of ZnO respond much more strongly to the presence of SO{sub 2} than Cs atoms supported on O-terminated terraces. The bonding interactions between the ZnO(0001)-Zn face and SO{sub 2} are weak, and promotion with Cs adatoms considerably improves the energetics for SO{sub 2} adsorption.

• Research Organization: Brookhaven National Laboratory (BNL), Upton, NY
• Sponsoring Organization: USDOE, Washington, DC (United States); North Atlantic Treaty Organization, Brussels (Belgium)
• DOE Contract Number: AC02-98CH10886
• OSTI ID: 335238
• Journal Information: Journal of Physical Chemistry B: Materials, Surfaces, Interfaces, amp Biophysical, Journal Name: Journal of Physical Chemistry B: Materials, Surfaces, Interfaces, amp Biophysical Journal Issue: 11 Vol. 103; ISSN 1089-5647; ISSN JPCBFK
• Country of Publication: United States
• Language: English

Related Subjects

33 ADVANCED PROPULSION SYSTEMS
54 ENVIRONMENTAL SCIENCES
ADSORPTION
CESIUM
CHEMICAL BONDS
CHEMICAL REACTIONS
CLUSTER MODEL
MOLYBDENUM OXIDES
SULFUR DIOXIDE
SYNCHROTRON RADIATION
TEMPERATURE DEPENDENCE
ZINC OXIDES