Unveiling nanoscale heterogeneities at the bias-dependent Gold-Electrolyte Interface

Electrified solid-liquid interfaces are extremely complex and dynamic, affecting both 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 solidliquid interfacial energy of a polycrystalline Au(111) electrode in neutral aqueous electrolyte, through in-situ electrochemical atomic force microscopy (EC-AFM). We acquire potential-dependent maps of the local interfacial adhesion forces, which we associate to the formation energy of the electric double layer. We observe nanoscale in-homogeneities of interfacial adhesion force across the entire map area, indicating local differences in the ordering of 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 on the local molecular arrangement of the solid-liquid interface in-situ which will be relevant for the study of any electrocatalyst.