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Abstract:
CO adsorption and oxidation on Au-covered “O-poor” biphase α-Fe2O3(0001) have been studied with HREELS and TDS. We found that the amount of CO that the surface can bind at room temperature increases with the CO dose, indicating that the CO–surface interaction produces new adsorption sites. Surface reduction via carbon dioxide formation was identified as the mechanism responsible for this. Reduction does probably already occur during dosing since the CO molecules detected at the surface after dosing just occupy the produced sites but are not oxidized toward CO2. CO oxidation does not occur without the gold clusters at the surface under the given experimental conditions. According to a theoretical study by Hoh et al. [Res. Chem. Intermed 2015, 41, 9587] gold clusters weaken the bond of oxygen at the oxide surface, which might facilitate the consumption of these atoms for CO oxidation. Spectroscopic data provide evidence that the reduction induces electron charge accumulation in the oxide near the Fermi level. The reduced surface is active for CO oxidation in a Mars–van Krevelen-type mechanism at room temperature: oxygen bound to the sample surface reacts with subsequently dosed CO toward CO2.
