NDLI: Surface Pourbaix diagrams and oxygen reduction activity of Pt , Ag and Ni(111) surfaces studied by DFT

Content Provider	World Health Organization (WHO)-Global Index Medicus
Author	Hansen, Heine A. Rossmeisl, Jan Nørskov, Jens K.
Description	Country affiliation: Denmark Author Affiliation: Hansen HA ( Center for Atomic-scale Materials Design, Department of Physics, Technical University of Denmark, DK-2800, Lyngby, Denmark.)
Abstract	Based on density functional theory calculations we investigate the electrochemically most stable surface structures as a function of pH and electrostatic potential for Pt(111) , Ag(111) and Ni(111) , and we construct surface Pourbaix diagrams. We study the oxygen reduction reaction (ORR) on the different surface structures and calculate the free energy of the intermediates. We estimate their catalytic activity for ORR by determining the highest potential at which all ORR reaction steps reduce the free energy. We obtain self-consistency in the sense that the surface is stable under the potential at which that particular surface can perform ORR. Using the self consistent surfaces, the activity of the very reactive Ni surface changes dramatically, whereas the activity of the more noble catalysts Pt and Ag remains unchanged. The reason for this difference is the oxidation of the reactive surface. Oxygen absorbed on the surface shifts the reactivity towards the weak binding region, which in turn increases the activity. The oxidation state of the surface and the ORR potential are constant versus the reversible hydrogen electrode (RHE). The dissolution potential in acidic solution, on the other hand, is constant vs. the standard hydrogen electrode ( SHE ). For Ag , this means that where the potential for dissolution and ORR are about the same at pH = 0, Ag becomes more stable relative to RHE as pH is increased. Hence the pH dependent stability offers an explanation for the possible use of Ag in alkaline fuel cell cathodes.
File Format	HTM / HTML
ISSN	14639076
Issue Number	25
Volume Number	10
e-ISSN	14639084
Journal	Physical Chemistry Chemical Physics
Language	English
Publisher	Royal Society of Chemistry
Publisher Date	2008-07-07
Publisher Place	Great Britain (UK)
Access Restriction	Subscribed
Subject Keyword	Discipline Physics Discipline Biophysics Discipline Chemistry Models, Chemical Nickel Chemistry Oxygen Platinum Silver Adsorption Catalysis Electric Power Supplies Electrochemistry Electrodes Hydrogen Bonding Hydrogen-ion Concentration Hydroxides Models, Molecular Oxidation-reduction Peroxides Static Electricity Surface Properties Thermodynamics Water Journal Article Research Support, Non-u.s. Gov't
Alternative Title	Surface Pourbaix diagrams and oxygen reduction activity of Pt, Ag and Ni(111) surfaces studied by DFT
Content Type	Text
Resource Type	Article
Subject	Physics and Astronomy Physical and Theoretical Chemistry

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