High energy ball-milled Ti 2 RuFe electrocatalyst for hydrogen evolution in the chlorate industry
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High energy ball-milled Ti2 RuFe electrocatalyst for hydrogen evolution in the chlorate industry Marco Blouin and Daniel Guaya) ´ INRS-Energie et Mat´eriaux, 1650 Boulevard Lionel-Boulet, C.P. 1020, Varennes, Qu´ebec, Canada J3X 1S2
Jacques Huot and Robert Schulz Technologie des Mat´eriaux, Institut de Recherche d’Hydro–Qu´ebec, 1800 Boulevard Lionel-Boulet, Varennes, Qu´ebec, Canada J3X 1S1 (Received 9 May 1996; accepted 5 February 1997)
The high energy mechanical alloying of a Ti –Ru– Fe powder mixture (atomic ratio 2 : 1 : 1) has been performed by extensive ball-milling in a steel crucible. The structural evolution of the resulting materials has been studied by x-ray powder diffraction analysis. The identification of the various phases present in the materials, as well as the crystallite size and strain, has been performed by Rietveld refinement analysis. In the first stage of the material transformation, Ru or Fe atoms dissolved into Ti to yield to the formation of b –Ti. Upon further ball-milling, almost all the original constituents of the powder mixture have disappeared and a new simple cubic Ti2 RuFe phase is formed, with a crystallite size as small as 8 nm. The electrochemical properties of these materials have been tested in a typical chlorate electrolyte by cold-pressing the powders into disk electrodes. At 20 h of ball-milling, where the phase concentration of Ti2 RuFe reaches 96%, a reduction of the activation overpotential at 250 mA cm22 of nearly 250 mV is observed when compared to that of a pure iron electrode.
I. INTRODUCTION
Since the introduction of the highly active and stable Dimensionally Stable Anode (DSA ) in the chlorate industry, not much energy savings can be expected from the development of new electrodes of the oxidation of chlorine ions. There is no such equivalent as the DSA electrode for the cathodic side of the reaction. The activation overpotential of the steel cathodes that are usually used in the chlorate industry is about one order of magnitude larger than that of the DSA anodes. This constitutes the main energy losses in the chlorate production and important energy savings and cost reduction could be gained by lowering the cathodic overpotential. Recently, nanocrystalline solids have emerged as an important field of research in materials science.1,2 A nanocrystalline solid is made of extremely small crystals, typically of the order of a few nanometers, and thus, the ratio of atoms located at the surface of the crystals over that in the volume is high compared to that found in larger crystals. Nanocrystalline solids can be obtained by the evaporation-condensation technique3 or by heattreating some amorphous metals.4,5 Recently, the high energy mechanical alloying technique has been used extensively to produce nanocrystalline materials.6 In this technique, repeated mechanical deformations create a)
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http://journals.cambridge.org
J. Mater. Res., Vol. 12, No. 6, Jun 1997
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