title: Oxygen as redox mediator in scanning electrochemical microscopy. Application to the study of localised acid attack of marble.
abstract: Oxygen from air-saturated aqueous solutions was employed as redox mediator in SECM experiments. Accurate approach curves under negative-feedback conditions were obtained using platinum and gold microelectrodes. Imaging experiments were also carried out, using a 2.5 microns gold microelectrode and oxygen that acted as distance mediator. The topographic images of a glass surface and that of a marble surface prior and after localised acid attack were recorded. High concentrations of hydrogen ions were produced locally, at the microelectrode tip held 3 microns above the marble surface, by applying a large enough positive potential within the oxygen evolution region. Under these conditions, the dissolution of CaCO3 occurred. Pits were produced, and the crater volumes thus obtained were linearly dependent on the electrolysis time.
authors.affiliation: Department of Physical Chemistry, University of Venice, Calle Larga S. Marta, 2137, 30123 Venice, Italy.
authors.forename: Carlo
authors.initials: C
authors.lastname: Bragato
authors.forename: Salvatore
authors.initials: S
authors.lastname: Daniele
authors.forename: Maria Antonietta
authors.initials: MA
authors.lastname: Baldo
authors.forename: Guy
authors.initials: G
authors.lastname: Denuault
mesh_terms: D000143:Acids / Q000737:chemistry*; D002119:Calcium Carbonate / Q000737:chemistry*; D004563:Electrochemistry; D006863:Hydrogen-Ion Concentration; D008855:Microscopy, Electron, Scanning; D008962:Models, Theoretical; D010084:Oxidation-Reduction; D010100:Oxygen / Q000737:chemistry*; D013499:Surface Properties
chemical_list: D000143:Acids; D002119:Calcium Carbonate; D010100:Oxygen