Energetics of Adsorbed Methanol and Methoxy on Ni(111): Comparisons to Pt(111)

The heats of adsorption of methanol molecularly adsorbed on clean Ni(111) and dissociatively adsorbed on oxygen-precovered Ni(111) were measured by single-crystal adsorption calorimetry (SCAC). The dissociative adsorption of methanol on oxygen-precovered Ni(111) produces adsorbed methoxy and hydroxy...

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Veröffentlicht in:ACS catalysis 2018-11, Vol.8 (11), p.10089-10095
Hauptverfasser: Carey, Spencer J, Zhao, Wei, Harman, Elizabeth, Baumann, Ann-Katrin, Mao, Zhongtian, Zhang, Wei, Campbell, Charles T
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Sprache:eng
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Zusammenfassung:The heats of adsorption of methanol molecularly adsorbed on clean Ni(111) and dissociatively adsorbed on oxygen-precovered Ni(111) were measured by single-crystal adsorption calorimetry (SCAC). The dissociative adsorption of methanol on oxygen-precovered Ni(111) produces adsorbed methoxy and hydroxyl, resulting in an integral heat of adsorption of −70. kJ/mol at a coverage of 0.25 ML. From this, the heat of formation of this adsorbed methoxy and the dissociation enthalpy of its bond to Ni(111) are estimated to be −233 and 250. kJ/mol, respectively. Analyzing previously measured bond enthalpies of monodentate formate and hydroxyl to Ni(111), we find a linear trend with a slope of 1 between the bond enthalpies of oxygenates to the Ni(111) surface and their corresponding gas-phase hydrogen–ligand bond dissociation enthalpies, similar to the trend for Pt(111) but ∼69 kJ/mol stronger. We also compare our experimentally measured energetics for adsorbed methanol and adsorbed methoxy with density functional theory (DFT) calculations with periodic boundary conditions from previous literature. These energetic values and trends help clarify selectivity, reaction rate, and activity differences between metal surfaces in reactions involving adsorbed oxygenates.
ISSN:2155-5435
2155-5435
DOI:10.1021/acscatal.8b02992