Electrodeposition of zirconium in an amide-type hydrophobic ionic liquid containing zirconium tetrachloride

Electrochemical behavior of zirconium tetrachloride (ZrCl₄) was investigated in an amide-type hydrophobic ionic liquid, 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl) amide (BMPTFSA). ZrCl₄ was found to be soluble in BMPTFSA with or without addition of 1-butyl-1-methylpyrrolidinium chloride (BMPCl) as a Lewis base. Cyclic voltammograms recorded at a glassy carbon (GC) electrode showed two noticeable reduction peaks at about –1.9 V and –2.3 V for the ZrCl₄ in ionic liquid without addition of BMPCl at room temperature, while no reduction peak was noticed for the ZrCl₄ in ionic liquid in the presence of BMPCl at room temperature. The absence of any cathodic current peak corresponding to the reduction of Zr(IV) in ionic liquid with BMPCl at room temperature is presumably ascribed to the formation of a stable anion, [ZrCl₆ ]^2– by addition of excess chloride ion to the electrolyte. Electrodeposition of Zr from ZrCl₄ on a GC electrode substrate in BMPTFSA ionic liquid with or without addition of BMPCl at elevated temperature or room temperature was observed. Scanning electron microscopy, energy dispersive X-ray and X-ray photoelectron spectroscopy results confirmed the presence of Zr in the deposits obtained by electrolysis of ZrCl₄ in BMPTFSA.