Interaction of CO with OH on Au(111): HCOO, CO3, and HOCO as Key Intermediates in the Water-Gas Shift Reaction

Journal Article · Thu Jan 01 04:00:00 EST 2009 · Journal of Physical Chemistry C

DOI:https://doi.org/10.1021/jp908169s· OSTI ID:1020139

Senanayake, S; Stacchiola, D; Liu, P; Mullins, C; Hrbek, J; Rodriguez, J

We have investigated the role of formate (HCOO), carbonate (CO{sub 3}), and carboxyl (HOCO) species as possible intermediates in the OH{sub ads} + CO{sub gas} {yields} CO{sub 2,gas} + 0.5H{sub 2,gas} reaction on Au(111) using synchrotron-based core level photoemission, near-edge X-ray absorption fine structure (NEXAFS), and infrared absorption spectroscopy (IR). Adsorbed HCOO, CO{sub 3}, and OH species were prepared by adsorbing formic acid, carbon dioxide, and water on a Au(111) surface precovered with 0.2 ML of atomic oxygen, respectively. HCOOH interacts weakly with Au(111), but on O/Au(111) it dissociates its acidic H to yield adsorbed formate. The results of NEXAFS, IR, and density-functional calculations indicate that the formate adopts a bidentate configuration on Au(111). Since the HCOO groups are stable on Au(111) up to temperatures near 350 K, it is not likely that formate is a key intermediate for the OH{sub ads} + CO{sub gas} {yields} CO{sub 2,gas} + 0.5H{sub 2,gas} reaction at low temperatures. In fact, the formation of this species could lead eventually to surface poisoning. When compared to a formate species, a carbonate species formed by the reaction of CO{sub 2} with O/Au(111) has low stability, decomposing at temperatures between 100 and 125 K, and should not poison the gold surface. Neither HCOO nor CO{sub 3} was detected during the reaction of CO with OH on Au(111) at 90-120 K. The results of photoemission and IR spectroscopy point to HO {leftrightarrow} CO interactions, consistent with the formation of an unstable HOCO intermediate which has a very short lifetime on the gold surface. The possible mechanism for the low-temperature water-gas shift on gold catalysts is discussed in light of these results.

• Research Organization: Brookhaven National Laboratory (BNL) National Synchrotron Light Source
• Sponsoring Organization: DOE - OFFICE OF SCIENCE
• DOE Contract Number: AC02-98CH10886
• OSTI ID: 1020139
• Report Number(s): BNL--95989-2011-JA
• Journal Information: Journal of Physical Chemistry C, Journal Name: Journal of Physical Chemistry C Journal Issue: 45 Vol. 113; ISSN 1932-7447
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
ABSORPTION
ABSORPTION SPECTROSCOPY
CARBON DIOXIDE
CARBONATES
CATALYSTS
CONFIGURATION
FINE STRUCTURE
FORMATES
FORMIC ACID
GOLD
LIFETIME
OXYGEN
PHOTOEMISSION
POISONING
SPECTROSCOPY
STABILITY
WATER
WATER GAS
national synchrotron light source