Electrochemistry offers a direct route to tune materials properties, e.g. to address practical problems such as water electrolysis and batteries, electro-catalysis, photo-catalytic water splitting or corrosion. Utilizing these possibilities requires knowledge of the surface structures that form when a solid is immersed in an aqueous electrolyte and how their stability is influenced by the presence of the electrolyte. Constructing an electrochemical surface Pourbaix diagram, which depicts the stability of the polar (0001) surface of ZnO as a function of pH and electrode potential U, we find that solvation effects are highly selective and play an active role in shaping the surface. They have little impact on surfaces with metallic character, but largely stabilize semiconducting structures, particularly ones that have a high electrostatic penalty in vacuum. This high selectivity has direct consequences for the surface phase diagrams and explains why certain catalytically interesting structures are thermodynamically highly unstable in vacuum but can be stabilized in a carefully selected electrochemical environment.

Selective solvent induced stabilization of polar oxide surfaces in electrochemical environment

2019 Fall National Meeting

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