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Title: Promotional Effect of Hydroxyl on the Aqueous Phase Oxidation of Carbon Monoxide and Glycerol over Supported Au Catalysts

Abstract

Gold particles supported on carbon and titania were explored as catalysts for oxidation of CO or glycerol by O{sub 2} at room temperature in liquid-phase water. Although Au/carbon catalysts were not active for vapor phase CO oxidation at room temperature, a turnover frequency of 5 s{sup -1} could be achieved with comparable CO concentration in aqueous solution containing 1 M NaOH. The turnover frequency on Au/carbon was a strong function of pH, decreasing by about a factor of 50 when the pH decreased from 14 to 0.3. Evidently, a catalytic oxidation route that was not available in the vapor phase is enabled by operation in the liquid water at high pH. Since Au/titania is active for vapor phase CO oxidation, the role of water, and therefore hydroxyl concentration, is not as significant as that for Au/carbon. Hydrogen peroxide is also produced during CO oxidation over Au in liquid water and increasing the hydroxyl concentration enhances its formation rate. For glycerol oxidation to glyceric acid (C{sub 3}) and glycolic acid (C{sub 2}) with O{sub 2} (1-10 atm) at 308-333 K over supported Au particles, high pH is required for catalysis to occur. Similar to CO oxidation in liquid water, H{sub 2}O{submore » 2} is also produced during glycerol oxidation at high pH. The formation of the C-C cleavage product glycolic acid is attributed to peroxide in the reaction.« less

Authors:
; ;
Publication Date:
Research Org.:
Brookhaven National Laboratory (BNL) National Synchrotron Light Source
Sponsoring Org.:
Doe - Office Of Science
OSTI Identifier:
930432
Report Number(s):
BNL-81176-2008-JA
Journal ID: ISSN 1022-5528; TRN: US200904%%540
DOE Contract Number:
DE-AC02-98CH10886
Resource Type:
Journal Article
Resource Relation:
Journal Name: Topics in Catalysis; Journal Volume: 44; Journal Issue: 39449
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; AQUEOUS SOLUTIONS; CARBON MONOXIDE; GLYCEROL; OXIDATION; CATALYTIC EFFECTS; GOLD; ANIONS; HYDROXIDES; CHEMICAL REACTION KINETICS; national synchrotron light source

Citation Formats

Ketchie,W., Murayama, M., and Davis, R. Promotional Effect of Hydroxyl on the Aqueous Phase Oxidation of Carbon Monoxide and Glycerol over Supported Au Catalysts. United States: N. p., 2007. Web. doi:10.1007/s11244-007-0304-x.
Ketchie,W., Murayama, M., & Davis, R. Promotional Effect of Hydroxyl on the Aqueous Phase Oxidation of Carbon Monoxide and Glycerol over Supported Au Catalysts. United States. doi:10.1007/s11244-007-0304-x.
Ketchie,W., Murayama, M., and Davis, R. Mon . "Promotional Effect of Hydroxyl on the Aqueous Phase Oxidation of Carbon Monoxide and Glycerol over Supported Au Catalysts". United States. doi:10.1007/s11244-007-0304-x.
@article{osti_930432,
title = {Promotional Effect of Hydroxyl on the Aqueous Phase Oxidation of Carbon Monoxide and Glycerol over Supported Au Catalysts},
author = {Ketchie,W. and Murayama, M. and Davis, R.},
abstractNote = {Gold particles supported on carbon and titania were explored as catalysts for oxidation of CO or glycerol by O{sub 2} at room temperature in liquid-phase water. Although Au/carbon catalysts were not active for vapor phase CO oxidation at room temperature, a turnover frequency of 5 s{sup -1} could be achieved with comparable CO concentration in aqueous solution containing 1 M NaOH. The turnover frequency on Au/carbon was a strong function of pH, decreasing by about a factor of 50 when the pH decreased from 14 to 0.3. Evidently, a catalytic oxidation route that was not available in the vapor phase is enabled by operation in the liquid water at high pH. Since Au/titania is active for vapor phase CO oxidation, the role of water, and therefore hydroxyl concentration, is not as significant as that for Au/carbon. Hydrogen peroxide is also produced during CO oxidation over Au in liquid water and increasing the hydroxyl concentration enhances its formation rate. For glycerol oxidation to glyceric acid (C{sub 3}) and glycolic acid (C{sub 2}) with O{sub 2} (1-10 atm) at 308-333 K over supported Au particles, high pH is required for catalysis to occur. Similar to CO oxidation in liquid water, H{sub 2}O{sub 2} is also produced during glycerol oxidation at high pH. The formation of the C-C cleavage product glycolic acid is attributed to peroxide in the reaction.},
doi = {10.1007/s11244-007-0304-x},
journal = {Topics in Catalysis},
number = 39449,
volume = 44,
place = {United States},
year = {Mon Jan 01 00:00:00 EST 2007},
month = {Mon Jan 01 00:00:00 EST 2007}
}
  • Two Pt electrodes with different morphologies were prepared and studied using an oxygen-ion conducting solid electrolyte electrochemical cell. Electrode 1 had a very porous catalyst/solid electrolyte interface and hence a high exchange current density while electrode 2 had a much less porous interface and consequently a lower exchange current density. Open-circuit reaction rate measurements showed that the effective Pt surface areas of the two electrodes were similar. Carbon monoxide oxidation at temperatures from 623 to 773 K was performed over the two electrodes. Under similar gas phase conditions and at the same overpotentials electrode 1 showed a nonfaradaic modification ofmore » activity while electrode 2 did not (the current densities passed were very different due to a difference in the exchange current densities of the electrodes.) This suggests that the work functions of the two electrodes were not modified to the same extent by a similar imposed overpotential. A model is suggested whereby the kinetics of electrochemical oxygen supply to (or removal from) the electrode surface must be relatively fast compared to the rate of decomposition and reaction of an electrochemically induced spillover species to observe rate modifications.« less
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