Scanning probe microscopy and electrochemical studies of deposition on electrode surfaces

Abstract

SPM, optical microscopy, and electrochemical techniques are used to study a range of electrochemical deposition processes on carbon electrodes, particularly those associated with diffusion-controlled multiple nucleation. Anodic stripping voltammetry for analytical measurements using solid electrodes is addressed in the light of limitations arising from electrode heterogeneity, electrode morphology, inhibited electrodeposition, and incomplete stripping of deposited metal. It is shown, using direct imaging of electrode surfaces, that each of the preceding factors may produce significant deviations from ideal electrode behaviour. The electrochemical nucleation of silver on BDD is examined. Data are obtained for the nucleation rate by interpretation of the deposition voltammetry, and by inspection of in-situ optical microscopic images. The particle distributions are analyzed and a stochastic model of nucleation developed. A model for the potentiostatic nucleation and three dimensional growth of deposits on an electrode surface under hydrodynamic conditions is examined. A wall-tube and stirred cell are used to generate conditions in which the diffusion layer thickness is in the range 10 – 40 μm. It is shown that the model provides excellent fits to the experimental data. A previously unrecognised correlation between the morphology of the PbO2 deposits and their electrocatalytic activity is established. The morphology of the films are observed as a function of time and potential using in-situ AFM. Nanotrench arrays are fabricated on HOPG surfaces. Cyclic voltammetry in simple redox couples is used to provide experimental evidence that the voltammetric response of a graphite electrode is solely due to the edge plane sites, with the basal plane sites having no measurable contribution. Nanotrenches are used as templates in a simple method for generating random assemblies of metal nanobands. This method is shown to be effective for generating gold, silver and copper nanowires. The electrochemical properties of the array are investigated via cyclic voltammetry.