Die Sauerstoffreduktion aus schwach sauren und neutralen, ungepufferten Lösungen

Abstract

KurdassungMit Hilfe der Dreieckspannungsmethode wurde an blanken Platinelektroden die Sauerstoffreduktion aus schwach sauren, ungepufferten, wa$rigen Elektrolytlosungen untersucht. Die Diffusionsgrenzstromdichte der Protonen fuhrt zu einem Plateau in der Stromdichte-Potentialkurve. Es wurde ein Einflu$ der Art und der Konzentration der Anionen auf die Uberspannung festgestellt.

Near-surface ion distribution and buffer effects during electrochemical reactions

“…A shift of the plateau-like level towards positive current densities can be observed with increasing the total concentration of the buffer. This originates from the dominance of the boric acid at pH-values below 9 and its proton capturing properties (positive prefactor in eqn (23)). As for the acetate buffer, zero current was observed for all buffer concentrations at a potential that corresponds to a surface pH-value equal to the pH-value of the solution.…”

“…In the case when heterogeneous (electro)chemical reactions occur at the solid-liquid interface involving species i, additionally the consumption or production of species at the surface has to be taken into consideration. 22,23 The reaction rates of the chemical species then typically define the boundary conditions for the solution of their concentration profile at steady-state. When very fast kinetics and/or slow element transport keep the surface reaction in equilibrium, the concentration of species i is constant and defined by thermodynamics (Dirichlet boundary condition).…”