Surface Structure Dependence of SO₂ Interaction with Ceria Nanocrystals with Well-defined Surface Facets

Journal Article · Wed Dec 02 00:00:00 EST 2015 · Journal of Physical Chemistry. C

DOI:https://doi.org/10.1021/acs.jpcc.5b07946· OSTI ID:1234997

Tumuluri, Uma ^[1]; Li, Meijun ^[1]; Cook, Brandon G. ^[1]; Sumpter, Bobby G. ^[1]; Dai, Sheng ^[1]; Wu, Zili ^[1]

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1. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

The effects of the surface structure of ceria (CeO₂) on the nature, strength, and amount of species resulting from SO₂ adsorption were studied using in situ IR and Raman spectroscopies coupled with mass spectrometry, along with first-principles calculations based on density functional theory (DFT). CeO₂ nanocrystals with different morphologies, namely, rods (representing a defective structure), cubes (100 facet), and octahedra (111 facet), were used to represent different CeO₂ surface structures. IR and Raman spectroscopic studies showed that the structure and binding strength of adsorbed species from SO₂ depend on the shape of the CeO₂ nanocrystals. SO₂ adsorbs mainly as surface sulfites and sulfates at room temperature on CeO₂ rods, cubes, and octahedra that were either oxidatively or reductively pretreated. The formation of sulfites is more evident on CeO₂ octahedra, whereas surface sulfates are more prominent on CeO₂ rods and cubes. This is explained by the increasing reducibility of the surface oxygen in the order octahedra < cubes < rods. Bulk sulfites are also formed during SO₂ adsorption on reduced CeO₂ rods. The formation of surface sulfites and sulfates on CeO₂ cubes is in good agreement with our DFT results of SO₂ interactions with the CeO₂(100) surface. CeO₂ rods desorb SO2 at higher temperatures than cubes and octahedra nanocrystals, but bulk sulfates are formed on CeO₂ rods and cubes after high-temperature desorption whereas only some surface sulfates/sulfites are left on octahedra. This difference is rationalized by the fact that CeO₂ rods have the highest surface basicity and largest amount of defects among the three nanocrystals, so they bind and react with SO₂ strongly and are the most degraded after SO₂ adsorption cycles. The fundamental understanding obtained in this work on the effects of the surface structure and defects on the interaction of SO₂ with CeO₂ provides insights for the design of more sulfur-resistant CeO₂-based catalysts.

• Research Organization: Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States). Center for Nanophase Materials Sciences (CNMS); Energy Frontier Research Centers (EFRC) (United States). Center for Understanding and Control of Acid Gas-induced Evolution of Materials for Energy (UNCAGE-ME)
• Sponsoring Organization: USDOE Office of Science (SC), Basic Energy Sciences (BES)
• Grant/Contract Number: AC05-00OR22725; SC0012577
• OSTI ID: 1234997
• Journal Information: Journal of Physical Chemistry. C, Vol. 119, Issue 52; ISSN 1932-7447
• Publisher: American Chemical Society
• Country of Publication: United States
• Language: English

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36 MATERIALS SCIENCE