Nanoscale Electron Transfer Variations at Electrocatalyst-Electrolyte Interfaces Resolved by Conductive Atomic Force Microscopy.

Rational innovation of electrocatalysts requires detailed knowledge of spatial property variations across the solid-electrolyte interface. We introduce correlative atomic force microscopy (AFM) to simultaneously probe, and at the nanoscale, electrical conductivity, chemical-frictional, and morphological properties of a bimetallic copper-gold system for CO electroreduction. In air, water, and bicarbonate electrolyte, current-voltage curves reveal resistive CuO islands in line with local current contrasts, while frictional imaging indicates qualitative variations in the hydration layer molecular ordering upon change from water to electrolyte. Nanoscale current contrast on polycrystalline Au shows resistive grain boundaries and electrocatalytically passive adlayer regions. conductive AFM imaging in water shows mesoscale regions of low current and reveals that reduced interfacial electric currents are accompanied by increased friction forces, thus indicating variations in the interfacial molecular ordering affected by the electrolyte composition and ionic species. These findings provide insights into how local electrochemical environments and adsorbed species affect interfacial charge transfer processes and support building structure-property relationships in catalysis and energy conversion research.