The effective surface pH during reactions at the solid–liquid interface

By Katsounaros, Ioannis; Meier, Josef C.; Klemm, Sebastian O.; Topalov, Angel A.; Biedermann, P. Ulrich; Auinger, Michael & Mayrhofer, Karl J.J.
Published in Electrochemistry Communications NULL 2011

Abstract

In this work the activity of protons directly at the solid–liquid interface during a heterogeneous reaction is demonstrated without introducing any pH measurement device, in non-buffered and buffered solutions. Due to a simple approach we can experimentally demonstrate the relation between reaction rate and surface pH directly from the cyclic voltammograms. Clearly, the pH at a solid–liquid interface can be quite different from the bulk in unbuffered or insufficiently buffered solutions even at moderate reaction rates, in particular in the pH range of 4 to 10. However, at the given mass-transport conditions, well controlled by a rotating disk electrode, a buffer concentration of 10- 2 M is already sufficient to pin the surface pH to the bulk value at reaction rates of up to 1 mA cm- 2.

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