SVIBOR - Project code: 1-07-162

MINISTRY OF SCIENCE AND TECHNOLOGY

Strossmayerov trg 4, HR - 10000 ZAGREB
tel.: +385 1 459 44 44, fax: +385 1 459 44 69
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Project code: 1-07-162


SURFACE-ELECTROCHEMICAL CHARACTERIZATION OF METALS AND METAL OXIDES


Main researcher: VUKOVIĆ, MARIJAN (53936)


Assistants
Type of research: basic
Duration from: 01/01/91. to 12/31/95.
Papers on project (total): 41
Papers on project quoted in Current Contents: 23
Institution name: Institut "Ruđer Bošković", Zagreb (98)
Department/Institute: Center for Marine Research Zagreb
Address: Bijenička cesta 54
City: 10000 - Zagreb, Croatia
Communication
Phone: 385 (1) 4561-176
Fax: 385 (1) 420-437
Summary: The project represents the interdisciplinary approach of the methods of electrochemistry, surface chemistry and colloid chemistry in studying properties of metals and metal oxides as electrocatalysts, new materials in form of glassy metals and ceramic oxides, as well as in understanding their role in corrosion processes. During the work on the project, the electrocatalytic properties of ruthenium, rhodium and iridium coatings on titanium in the oxygen evolution reaction from acidic solution have been examined. It was found that both ruthenium and rhodium can be additionally electrochemically activated to the enhanced rate of oxygen evolution. In the case of ruthenium, as shown by X-ray photoelectron spectra, the reason is the increase of the hydroxyl component of the oxide layer. As far as the anodic stability is concerned, the most stable coating was rhodium, while ruthenium exhibited the lowest stability. Ruthenium coating can be stabilized by thermal treatment above 200oC as well as by the addition of iridium and formation of mixed Ru-Ir coating, which in the composition of Ru0.40Ir0.60 exhibited also electrochromic behaviour. It was potentiodynamically activated to the state of the enhanced electrocatalytic activity. In the process of passivation of glassy metal Fe80B20in acid solution, the adsorbed intermediates take place as well as the formation of inner oxide layer and outer protective sulphate layer. In neutral borate solution, an isolating n-type semiconductor layer was formed. The impedance of the electrode at passive potentials exhibits only capacitive component, while on the more positive potentials the adsorption component was also found. The electrokinetic data of complex oxide Pb(Zr0.52Ti0.48)O3 suspension obtained microelectrophore- tically, showed that in the overall electrokinetic behaviour of suspension, the role of PbO is predominant. The electrochemically induced growth of the hydrous oxide layer on the stainless steel led to the more stable surface against corrosion.

Keywords: electrochemistry, electrocatalysis, electrokinetics, corrosion,electrochemical oxygen evolution, metals, glassy-metals, metaloxides, ceramic, oxides, passive layers, cyclic voltammetry,electrochemical impedance spectroscopy, electrophoresis, rotatingring-disc electrode, ruthenium, rhodium, iridium, Fe80B20, passiveFe80B20, passive iron, stainless steel

Research goals: The investigation of the relationship between surface properties of metals and their oxides with their electrocatalytic, corrosive and rheological properties are of great importance both from theoretical and applied points of view. The aim of these investigations is a characterization of surfaces of materials and search for optimal conditions in which some electrochemical reactions operate and/or are inhibited, as well as defining the applicability of materials as (i) electrocatalysts, (ii) ceramic oxides, (iii) materials resistive to corrosion and (iv) experimental model systems. These investigations will contribute to the new insights on fundamental relationships between structural, chemical and electrical properties of surfaces with their electrocatalytic and/or corrosion processes on the solid/liquid interface. In electrocatalysis, in the case of oxygen and chlorine evolution reactions on oxides of ruthenium, rhodium and iridium, an attempt will be made to define those surface properties which bring to :(i) enhanced electrocatalytic activity and (ii) enhanced anodic stability. In the field of ceramic oxides, through measurements of their electrokinetic properties, a reproducible and stable suspensions of ceramic oxides will be prepared. In the case of corrosion of a glassy metal Fe80B20 as well as in the case of a passive layers formed by anodic oxidation of Fe80B20, the relationship between electrical properties of material and its corrosion properties in different electrolytes will be defined.

COOPERATION - PROJECTS


  1. Name of project: Corrossion implications and endurance prediction for NPP heat exchanger materials by rapid electrochemical measurement
    Name of institution: IAEA
    City: Beč, Austrija

  2. Name of project: Suspensions and microstructure of ceramics
    Name of institution: National Institute for Science and Technology
    City: Washington, USA
Other information about the project.
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Last update: 10/05/95
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