SEM, EDX and EIS study of an electrochemically modified electrode surface of natural enargite (Cu3AsS4)

Enargite electrodes, made from mineral originating in the ‘Salvador’ mine (Chañaral, Chile), have been studied using SEM, EDX, CV and EIS in an alkaline solution for a range of different potentials in the positive sweep direction (PSD) and negative sweep direction (NSD). The results of SEM and EDX have shown that the principal changes in morphology and chemical composition take place on the surface of the electrode for oxidation potentials close to the value that corresponds to the most intense peak in the PSD, where there is clearly formation of a layer of oxidised material with areas of morphology which are irregular and high in oxygen content. These results are in accordance with the findings from XPS studies published previously. The charge transfer resistance and the resistance of the anodic layer of the electrode were determined by EIS measurements; the values depend heavily on the applied potential in the PSD or NSD. These changes are related to the changes on the surface of the electrode studied by SEM and EDX