Preparation and characterization of RuO 2 –IrO 2 –SnO 2 ternary mixtures for advanced electrochemical technology Lourdes Vazquez-Gomez, Sergio Ferro, Achille De Battisti * Department of Chemistry, University of Ferrara, via L. Borsari 46, 44100 Ferrara, Italy Received 1 December 2005; received in revised form 10 March 2006; accepted 24 March 2006 Available online 16 May 2006 Abstract Electrochemical methods have proved to be particularly effective both for water detoxification (abatement of heavy metals and organic impurities) and sterilization, from natural resources to utilization points, combining these features with low costs and easier handling of equipments. The efficiency of electrochemical methods strongly depends on electrode nature, anodes being of particular importance because they must stand much more severe polarization conditions and have to exhibit good catalytic activity for complex reactions like oxygen and chlorine evolution. The present work is devoted to the preparation and characterization of mixed-oxide electrode coatings based on IrO 2 , RuO 2 and SnO 2 , with the scope of finding optimal compositions guaranteeing longer service-life under the critical conditions where oxygen evolution is concomitant with chloride oxidation. # 2006 Elsevier B.V. All rights reserved. Keywords: Electrocatalysis; Oxide electrodes; Chlorine evolution reaction; Oxygen evolution reaction; Water sterilization 1. Introduction The challenge of the increasing demand for quality water can be met only applying all suitable scientific and technical methods to increase the productivity of process technology for the conversion of low-grade water into pure water. Sterilization and elimination of organic micro-impurities from drinkable water and water for surgery-medical use is of utmost importance [1]. Many different methods for improving the water quality are already established: these include membrane-based methods, ultra- and micro-filtration, biological, chemical, physico- chemical treatments. More traditional purification methods, although generally quite effective for the destruction of bacterial and fungine pollutants, as well as for organic/inorganic chemical impurities, may result relatively ineffective for the elimination of viral components and residual organic substrates [2]. A solution to these problems can be sought in advanced electrochemical technologies based on electric field and Faradaic effects in specially designed electrochemical cells, readily installed at the consumption sites. Two main types of treatment can be considered [3]: 1. Drinkable waters suffering degradation of properties (due to lengthy routes, pipe damages, uphill-treatment problems) may be subjected to a ‘‘direct’’ electrochemical treatment, i.e., the water is passed through anodic and cathodic compartments of one or more electrochemical cells with specific features. The process depends on applied electric field, pH ‘‘shock’’ and Faradaic processes (anodic oxidation, cathodic reduction) and results in the elimination of biological and chemical impurities (traces of heavy metals) and in the abatement of the redox potential to 0.10 (vs. SCE). 2. Good quality water for surgery, food industry, etc. may be obtained through an ‘‘indirect’’ treatment, adding suitable amounts of so-called ‘‘neutral anolytes’’, which are produced by electrolyzing diluted brines; under optimal conditions, a complete elimination of the biological and chemical impurities can be obtained. Both treatments prove to be effective, requiring low energy consumption while ensuring long service-life and low costs. Concerning the disadvantages, the possible need for frequent maintenance applies in particular for the direct-treatment concept. The above technology has already found practical applica- tions and its further development requires improvement of cell www.elsevier.com/locate/apcatb Applied Catalysis B: Environmental 67 (2006) 34–40 * Corresponding author. Tel.: +39 0532 291124; fax: +39 0532 240709. E-mail address: dbtcll@unife.it (A. De Battisti). 0926-3373/$ – see front matter # 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.apcatb.2006.03.023