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- Holm, Alexander, 1983-, et al.
(författare)
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A Water-Promoted Mars-van Krevelen Reaction Dominates Low-Temperature CO Oxidation over Au-Fe2O3 but Not over Au-TiO2
- 2024
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Ingår i: ACS Catalysis. - 2155-5435. ; 14:5, s. 3191-3197
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Tidskriftsartikel (refereegranskat)abstract
- We provide experimental evidence that is inconsistent with often proposed Langmuir−Hinshelwood (LH) mechanistic hypotheses for water-promoted CO oxidation over Au–Fe2O3. Passing CO and H2O, but no O2, over Au-γ-Fe2O3 at 25 °C, we observe significant CO2 production, inconsistent with LH mechanistic hypotheses. Experiments with H218O further show that previous LH mechanistic proposals cannot account for water-promoted CO oxidation over Au-γ-Fe2O3. Guided by density functional theory, we instead postulate a water-promoted Mars–van Krevelen (w-MvK) reaction. Our proposed w-MvK mechanism is consistent both with observed CO2 production in the absence of O2 and with CO oxidation in the presence of H218O and 16O2. In contrast, for Au-TiO2, our data is consistent with previous LH mechanistic hypotheses.
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| 2. |
- Boscolo Bibi, Sara, 1993-, et al.
(författare)
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Multi-spectroscopic study of electrochemically-formed oxide-derived gold electrodes
- 2024
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Ingår i: Physical Chemistry, Chemical Physics - PCCP. - : Royal Society of Chemistry. - 1463-9076 .- 1463-9084. ; 26:3, s. 2332-2340
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Tidskriftsartikel (refereegranskat)abstract
- Oxide-derived metals are produced by reducing an oxide precursor. These materials, including gold, have shown improved catalytic performance over many native metals. The origin of this improvement for gold is not yet understood. In this study, operando non-resonant sum frequency generation (SFG) and ex situ high-pressure X-ray photoelectron spectroscopy (HP-XPS) have been employed to investigate electrochemically-formed oxide-derived gold (OD-Au) from polycrystalline gold surfaces. A range of different oxidizing conditions were used to form OD-Au in acidic aqueous medium (H3PO4, pH = 1). Our electrochemical data after OD-Au is generated suggest that the surface is metallic gold, however SFG signal variations indicate the presence of subsurface gold oxide remnants between the metallic gold surface layer and bulk gold. The HP-XPS results suggest that this subsurface gold oxide could be in the form of Au2O3 or Au(OH)3. Furthermore, the SFG measurements show that with reducing electrochemical treatments the original gold metallic state can be restored, meaning the subsurface gold oxide is released. This work demonstrates that remnants of gold oxide persist beneath the topmost gold layer when the OD-Au is created, potentially facilitating the understanding of the improved catalytic properties of OD-Au.
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