The effective pH at the solid-liquid interface and the local ion distribution during complex electrochemical reactions

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Heterogeneous catalytic reactions in un- or only weakly buffered, neutral media, which are typical conditions for natural environments, are often dominated by the pH value directly at the liquid/solid interface. Although this is highly important and well-known for several research studies in various fields related to surface and interface chemistry, the effect of the interface pH and its complex relation to reaction rates of pH dependent reactions, mass transport of educts and products, and bulk pH value can only be determined quantitatively for very facile systems. In this project the effect of the interface pH and the whole ion distribution close to the electrode surface will be investigated on a fundamental level, in order to derive an improved understanding and a general model for heterogeneous reactions in neutral media. The experimental investigations are based on special ion-selective, local methods, which are applied initially for facile reactions on ideal systems and later for kinetically constrained reactions like the electrochemical oxygen reduction even on inhomogeneous, realistic surfaces. The understanding of the complex relationships that affect the interface pH will be finally utilized for the improvement of applications in corrosion protection and related topics.