Morphology, Microstructure and Electrocatalytic Properties of Activated Copper Surfaces

The deliberate manipulation of electrodic surfaces consists of an area of continuing interest, because this approach leads to an improvement in the ability to recognize molecules and carry out electron transfer processes at higher rates. Hence, one of the dominant subjects in electrochemistry is the attempt to control the chemical composition and morphological structure of the electrode surface to gain advantages in electroanalytical determinations. It is well known that the electroactivity of copper surfaces depends strongly on their morphology, surface area and structure, which would in turn depend on the method employed to prepare the electrode prior to electrochemical measurements. Hence, several studies have been reported in the literature on the use of copper surfaces aiming for the quantification of different species such as glucose, carbohydrates, ethanol, nitrate, 5 nitrite, and sufite. The electrochemical determination of nitrate after deposition of copper from solutions containing Cu(II) has been reported by some authors, who examined qualitatively the morphology of the copper deposit by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The increased sensitivity for nitrate after the surface modification by deposition of the fresh copper layer was attributed to morphologic changes assessed through quantitative parameters such as roughness and porosity of the film. Our group reported a new procedure for the activation of copper surfaces using a potential protocol based on copper oxidation and subsequent reduction of generated copper ions. Taking into account these findings and as an attempt to understand which surface parameters control the electrochemical activity, the present study aims to evaluate whether there is a quantitative correlation between the surface area of copper electrodes and their electrochemical properties. Accordingly, copper electrodes were activated for different periods of time to produce layers which were analyzed by SEM and AFM. Then, the electrochemical activity of each generated surface was evaluated towards the cathodic reduction of nitrite. To the best of our knowledge, this is the first time that such a quantitative approach is applied for copper electrodes.