Interfacial optical anisotropy of Cu(110) electrochemistry using singular value decomposition

Understanding surface/interface states (SIs) in metal–electrolyte environments is crucial for diverse scientific and technological fields. This work investigates the reflectance anisotropy spectroscopy (RAS) of Cu in HCl solution to gain deeper insights. Using the singular-value decomposition (SVD) method, we extract three distinct RAS features that track electrochemical changes. We argue that these features stem from surface-induced bulk optical anisotropies and Cl adsorption. Their correlation with cyclic voltammetry (CV) further supports this interpretation. Specifically, we link these lineshapes to HCl adsorption, and microscale surface roughness resembling a lamellar grating, as verified by electrochemical scanning tunneling microscopy (EC-STM), and another one correlated to ab initio calculations bearing transitions between bulk and surface states of Cu. Our findings shed light on SIs behavior in metal–electrolyte interfaces. The combination of SVD and RAS establishes a robust methodology for studying metallic surfaces in electrochemical systems, enabling comparisons with ab initio predictions.