title: Near-surface ion distribution and buffer effects during electrochemical reactions.
abstract: The near-surface ion distribution at the solid-liquid interface during the Hydrogen Oxidation Reaction (HOR)/Hydrogen Evolution Reaction (HER) on a rotating platinum disc electrode is demonstrated in this work. The relation between reaction rate, mass transport and the resulting surface pH-value is used to theoretically predict cyclic voltammetry behaviour using only thermodynamic and diffusion data obtained from the literature, which were confirmed by experimental measurements. The effect of buffer addition on the current signal, the surface pH and the ion distribution is quantitatively described by analytical solutions and the fragility of the surface pH during reactions that form or consume H(+) in near-neutral unbuffered solutions or poorly buffered media is highlighted. While the ideal conditions utilized in this fundamental study cannot be directly applied to real scenarios, they do provide a basic understanding of the surface pH concept for more complex heterogeneous reactions.
authors.affiliation: Department of Interface Chemistry and Surface Engineering, Max-Planck-Institut für Eisenforschung GmbH, Max-Planck-Strasse 1, D-40237 Düsseldorf, Germany. auinger@mpie.de
authors.forename: Michael
authors.initials: M
authors.lastname: Auinger
authors.forename: Ioannis
authors.initials: I
authors.lastname: Katsounaros
authors.forename: Josef C
authors.initials: JC
authors.lastname: Meier
authors.forename: Sebastian O
authors.initials: SO
authors.lastname: Klemm
authors.forename: P Ulrich
authors.initials: PU
authors.lastname: Biedermann
authors.forename: Angel A
authors.initials: AA
authors.lastname: Topalov
authors.forename: Michael
authors.initials: M
authors.lastname: Rohwerder
authors.forename: Karl J J
authors.initials: KJ
authors.lastname: Mayrhofer
mesh_terms: D002021:Buffers; D004058:Diffusion; D055664:Electrochemical Techniques; D004566:Electrodes; D006859:Hydrogen / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D007477:Ions / Q000737:chemistry*; D010084:Oxidation-Reduction; D010984:Platinum / Q000737:chemistry; D013816:Thermodynamics
chemical_list: D002021:Buffers; D007477:Ions; D010984:Platinum; D006859:Hydrogen