Cathodic reactions on an iron RDE in the presence of Y(III)

During electrolysis of a solution containing Y(III) ions, a hydrous Y(OH)(3) film forms in the alkaline layer close to a hydrogen-evolving cathode. The film hinders the reduction of dissolved oxygen and activates the reduction of water, hydrogen evolution. The ability to hinder certain reactions while catalyzing hydrogen evolution may be useful in electrolysis applications. In this work the electrochemical properties of an in situ formed yttrium-hydroxide film were studied on an iron rotating disk electrode (RDE) in 0.5 M NaCl with addition of YCl3, NaClO, and of NaNO3. It was found that the film also hinders the reduction of protons, hypochlorite ions, and nitrate ions. At low concentration of Y(III) or at high current density, when the hydrogen evolution was vigorous, no activation of hydrogen evolution was observed. Under these conditions the film still hindered the reduction of ions. The reactant in the catalyzed hydrogen evolution reaction is most likely water molecules within the hydrous film. Nitrate ions were easily reduced on an iron cathode when no Y(III) ions were present in the solution. When studying effects of yttrium addition to a chloride solution the use of YCl3, rather than Y(NO3)(3), as Y(III) source is recommended. (C) 2008 The Electrochemical Society.