Voltammetry and potential-dependent forces between a Si3N4 cantilever and a Cu(111) surface are used to probe the oxidation and reduction of this material in basic solution. In the anodic sweep, potential-dependent adhesive forces obtained from the cathodic limit to the first anodic peak indicate the occurrence of hydroxide adsorption at more negative potentials than the formation of Cu2O. The reactions through the Cu2O formation peak are diagnosed as competing scan-rate-dependent reactions that include the oxidation of Cu with both adsorbed OH- and solution OH-. The formation of Cu2O and soluble materials is evident from force measurements. The second anodic peak is associated with a two-electron-transfer reaction along with irreversible reactions producing soluble copper oxide species. The change of adhesive forces in the region of this peak indicates that Cu(OH)2 is formed first and converted to more stable CuO on the surface. Force and scanrate-dependent voltammetric measurements indicate that the two cathodic peaks correspond to the combination of reduction of soluble and insoluble (adsorbed) copper species. CuOH is a likely intermediate in the final reduction to Cu metal on the cathodic scan. The combination of voltammetry and force spectroscopy provides new insights into the mechanism of the important Cu oxidation process.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry
- Surfaces, Coatings and Films
- Materials Chemistry