Electrochemical Behavior of Silver Halogenocomplexes in an Amide-Type Ionic Liquid

Abstract

The electrochemical behavior of halogenocomplexes of Ag was investigated in an amide-type ionic liquid, 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)amide (BMPTFSA) in the presence of the corresponding halogen anion. Silver halides, AgX (X– = Cl–, Br–, and I–) were found to be soluble in BMPTFSA containing 0.5 M BMPX by forming [AgX3]2–. The cathodic reduction of [AgX3]2– to metallic Ag was possible within the electrochemical window of BMPTFSA. The reduction potentials were in the order of [AgCl3]2– > [AgBr3]2– > [AgI3]2–. The morphology of Ag deposits depended on the reduction potential. The diffusion coefficients of [AgCl3]2–, [AgBr3]2–, and [AgI3]2– were 2.5, 2.0, and 1.6 × 10–7 cm2 s–1, respectively. Formation of Ag nanoparticles dispersed in the ionic liquids was confirmed after potentiostatic cathodic reduction at –2.5 V using transmission electron microscopy.