Characterization of Different Au/Electrolyte Interfaces via In Situ Differential Cyclic Plasmo-Voltammetry

In this article, we describe an improved method that uses in situ plasmonic spectroscopy to reliably track changes of the metal-electrolyte interface over a large potential window. Utilizing the specific sensitivity of the plasmonic resonance toward changes in the interfacial properties of nanoparticles (NPs), processes such as double-layer charging, surface oxidation/reduction, adsorption and desorption of anions, as well as metal under- and overpotential deposition are resolved. The main contributions to this signal are changes in the charge of the NPs and chemical interface damping due to the adsorbed species. We employ highly homogeneous macroscopic Au nanoarrays with controlled interfaces produced by lift-off nanoimprint lithography (LO-NIL) as the working electrodes for multiparticle differential cyclic plasmo-voltammetry (dCPV). First, plasmonic signals are recorded and compared to known electrochemical processes before the plasmonic signals are used to gain insights beyond those achievable by electrochemical means. These include observation of forced HSO₄^- and H₂PO₄^- desorption by the onset of the Au oxidation and resolution of the different steps of the monolayer buildup during Cu underpotential deposition on Au.