Initial Stages of Water Adsorption on Au Surfaces

Ikemiya, Norihito; Gewirth, Andrew A.

doi:10.1021/ja972322h

Cited by 45 publications

(50 citation statements)

References 23 publications

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“…It is difficult to rationalize the water inhibition data above if the entire metal surface participates in H 2 activation. The van der Waals interactions between Au and water are so weak that Au is considered to be essentially hydrophobic, − and water adsorption on Au surfaces is only observed at very low temperatures. − In comparison, water readily engages in hydrogen-bonding interactions with support hydroxyl groups during physisorption. Further, our previous volumetric and infrared spectroscopic water adsorption studies are consistent with water adsorption on the support rather than the Au .…”

Section: Resultsmentioning

confidence: 99%

H₂Oxidation over Supported Au Nanoparticle Catalysts: Evidence for Heterolytic H₂Activation at the Metal–Support Interface

et al. 2018

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Water adsorbed at the metal-support interface (MSI) plays an important role in multiple reactions. Due to its importance in CO preferential oxidation (PrOx), we examined H oxidation kinetics in the presence of water over Au/TiO and Au/AlO catalysts, reaching the following mechanistic conclusions: (i) O activation follows a similar mechanism to that proposed in CO oxidation catalysis; (ii) weakly adsorbed HO is a strong reaction inhibitor; (iii) fast H activation occurs at the MSI, and (iv) H activation kinetics are inconsistent with traditional dissociative H chemisorption on metals. Density functional theory (DFT) calculations using a supported Au nanorod model suggest H activation proceeds through a heterolytic dissociation mechanism, resulting in a formal hydride residing on the Au and a proton bound to a surface TiOH group. This potential mechanism was supported by infrared spectroscopy experiments during H adsorption on a deuterated Au/TiO surface, which showed rapid H-D scrambling with surface hydroxyl groups. DFT calculations suggest that the reaction proceeds largely through proton-mediated pathways and that typical Brønsted-Evans Polanyi behavior is broken by introducing weak acid/base sites at the MSI. The kinetics data were successfully reinterpreted in the context of the heterolytic H activation mechanism, tying together the experimental and computational evidence and rationalizing the observed inhibition by physiorbed water on the support as blocking the MSI sites required for heterolytic H activation. In addition to providing evidence for this unusual H activation mechanism, these results offer additional insight into why water dramatically improves CO PrOx catalysis over Au.

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Section: Resultsmentioning

confidence: 99%

H₂Oxidation over Supported Au Nanoparticle Catalysts: Evidence for Heterolytic H₂Activation at the Metal–Support Interface

et al. 2018

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“…Water binds more strongly to itself than it does to Au (ref. 44); indeed, Au surfaces are considered hydrophobic and require cryogenic experiments to observe water adsorption 45 . This suggests the drop in activity is caused by water that is adsorbed on the support at the metal-support interface physically blocking CO from adsorbing on the Au particles.…”

Section: Resultsmentioning

confidence: 99%

Controlling activity and selectivity using water in the Au-catalysed preferential oxidation of CO in H2

et al. 2016

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“…Although there is no direct spectroscopic evidence to show that the interactions between water molecules and Au and Pt are different, we think that structure of water molecules in the first layer or in the vicinity of metal surface is very important to the whole interfacial water structure. STM studies showed a well ordered H 2 O film on a clean Pt surface 31 but an amorphous H 2 O film on a clean Au surface, 32 suggesting that the interaction of water molecules with the Pt surface is strong and that with the Au surface is weak. The stronger interaction between water molecules and Pt surface might be the origin of the higher order of interfacial water at the Pt surface.…”

Section: Methodsmentioning

confidence: 99%

Molecular structure at electrode/electrolyte solution interfaces related to electrocatalysis

2009

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The potential dependence of the interfacial water structure at Pt and Au thin film electrodes was investigated by sum frequency generation (SFG) spectroscopy in internal reflection mode. In the case of the Pt electrode, two broad peaks were observed in the OH stretching region at ca. 3200 cm(-1) and ca. 3400 cm(-1), which are known to be due to the symmetric OH stretching (upsilon1) of tetrahedrally coordinated, i.e., strongly hydrogen bonded "ice-like" water, and the asymmetric OH stretching (upsilon3) of water molecules in a more random arrangement, i.e., weakly hydrogen bonded "liquid-like" water, respectively. In the case of the Au electrode, however, a 3400 cm(-1) band was dominant in the SFG spectrum, suggesting that the interaction between water molecules and Au and Pt are different, i.e., water molecules are more disordered at the Au surface. The potential dependence of interfacial water during the methanol oxidation reaction on a Pt electrode was also investigated. SFG intensity strongly depended on electrode potential. Several possibilities are suggested for the potential dependence of the SFG intensity.

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Initial Stages of Water Adsorption on Au Surfaces

Cited by 45 publications

References 23 publications

H₂Oxidation over Supported Au Nanoparticle Catalysts: Evidence for Heterolytic H₂Activation at the Metal–Support Interface

H₂Oxidation over Supported Au Nanoparticle Catalysts: Evidence for Heterolytic H₂Activation at the Metal–Support Interface

Controlling activity and selectivity using water in the Au-catalysed preferential oxidation of CO in H2

Molecular structure at electrode/electrolyte solution interfaces related to electrocatalysis

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Initial Stages of Water Adsorption on Au Surfaces

Cited by 45 publications

References 23 publications

H2Oxidation over Supported Au Nanoparticle Catalysts: Evidence for Heterolytic H2Activation at the Metal–Support Interface

H2Oxidation over Supported Au Nanoparticle Catalysts: Evidence for Heterolytic H2Activation at the Metal–Support Interface

Controlling activity and selectivity using water in the Au-catalysed preferential oxidation of CO in H2

Molecular structure at electrode/electrolyte solution interfaces related to electrocatalysis

Contact Info

Product

Resources

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H₂Oxidation over Supported Au Nanoparticle Catalysts: Evidence for Heterolytic H₂Activation at the Metal–Support Interface

H₂Oxidation over Supported Au Nanoparticle Catalysts: Evidence for Heterolytic H₂Activation at the Metal–Support Interface