Unveiling Nanoscale Heterogeneities at the Bias-Dependent Gold-Electrolyte Interface.

Electrified solid-liquid interfaces (SLIs) are extremely complex and dynamic, affecting both the dynamics and selectivity of reaction pathways at electrochemical interfaces. Enabling access to the structure and arrangement of interfacial water in situ with nanoscale resolution is essential to develop efficient electrocatalysts. Here, we probe the SLI energy of a polycrystalline Au(111) electrode in a neutral aqueous electrolyte through in situ electrochemical atomic force microscopy. We acquire potential-dependent maps of the local interfacial adhesion forces, which we associate with the formation energy of the electric double layer. We observe nanoscale inhomogeneities of interfacial adhesion force across the entire map area, indicating local differences in the ordering of the solvent/ions at the interface. Anion adsorption has a clear influence on the observed interfacial adhesion forces. Strikingly, the adhesion forces exhibit potential-dependent hysteresis, which depends on the local gold grain curvature. Our findings on a model electrode extend the use of scanning probe microscopy to gain insights into the local molecular arrangement of the SLI in situ, which can be extended to other electrocatalysts.