High Sensitivity Bimetallic Electrode Generation through the Study of Copper Electrocrystallisation on Metallic Substrates (Md/Ms) in Acidic Media

Abstract

The electrochemical nucleation of copper on metallic substrates in acidic media was investigated using cyclic voltammetry and chronoamperometry. The purpose is to optimize the operating conditions for preparing a high sensitivity bimetallic electrode. Indeed, optimizing the electrodeposition parameters whereby two different metals are present: deposited metal Md and substrate metal Ms, allows the generation of a large number of microelectrodes, correspondingly, yield the largest active surface, and so, increasing the electrode sensitivity.The aim of this study is to highlight the positive impact of controlling the electrodeposition process of a metal on a substrate and determining the operation conditions towards the augmentation of the active surface area of an electrode.This work is focused on studying the first instance of copper nuclei formation on the electrode surface and the growth of these nuclei over time. Factors influencing deposit quality and allow to yield the highest specific surface area were considered, principally the overvoltage and the deposit cutoff charge. The nucleation phenomena and the initial growth of the copper nuclei on three different metallic substrates was studied. The plot of the experimental results were compared to theoretical models for the two possible nucleation modes: instantaneous and progressive. The nucleation phenomena was overseen on cyclic voltammetry recorded and the electrodeposition overvoltage were determined for each couple (Md/Ms). Chronoamperometric measurements evidenced that copper electrodeposition process involves progressive nucleation on the substrates, which was confirmed by scanning electron microscopy (SEM). Afterward, the germination rates were determined.The optimum theoretical cutoff charges were calculated from chronoamperograms using Faraday’s law and were experimentally verified.Optimal operating conditions were determined for the preparation of bimetallic electrodes with the largest active surface area. Subsequently, copper deposition runs were carried out on the three electrode substrates. The formed bimetallic electrodes were tested using square wave voltammetry for their ability to detect species requiring high sensitivity identification tools such as nitrates in seawater. In open ocean, the concentration of nitrates can drop from few dozens of micromolars to as littles as few nanomolars.The copper nuclei fount out to be unstable on the substrate in maritime area due to corrosion and attack by dissolved oxygen. A cathodic polarization by applying a direct current was applied to protect the deposited copper.