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

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 front 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). (C) 2011 Elsevier B.V. All rights reserved.