Spatial Imaging of Cu2+-Ion Release by Combining Alternating Current and Underpotential Stripping Mode Scanning Electrochemical Microscopy

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Abstract

Anodic underpotential stripping voltammetry was integrated into SECM in order to characterize local corrosion of metallic copper deposits on metal surfaces as a model for copper containing alloys. Primarily, the alternating current mode of SECM was applied in an electrolyte of low ionic strength for localizing possible corrosion sites without any perturbation of the corroding surface, e.g., by the presence of any redox mediator. Sequentially, the release of Cu2+-ions was confirmed and locally visualized at the previously detected electrochemically active sites by means of spatially resolved anodic underpotential stripping voltammetry performed during SECM scanning. Underpotential stripping voltammetry of Cu2+-ions was performed at a specifically developed 15 μm gold-coated Pt microelectrode used as SECM tip with a detection limit of 0.15 nM Cu2+ (N=4, RSD=6%) for an accumulation of 45 s at −0.4 V. SECM images of model samples such as copper coated microelectrodes and lacquered metallic copper workpieces demonstrated the feasibility and applicability of combining AC- and underpotential stripping mode of SECM for local visualization of Cu2+-ion release from corroding surfaces.

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