Electrode Reactions of Platinum Bromide Complexes in an Amide-Type Ionic Liquid

Abstract

The electrode reactions of platinum bromide complexes were investigated in an amide-type room-temperature ionic liquid, 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)amide (BMPTFSA). Platinum bromides were dissolved in BMPTFSA with addition of BMPBr. Ultraviolet and visible absorption spectra of the electrolytes revealed that Pt(II) and Pt(IV) species were dissolved as [Pt II Br 4 ] 2- and [Pt IV Br 6 ] 2- , respectively. The cyclic voltammogram in BMPTFSA containing 10 mM [Pt IV Br 6 ] 2- showed two reduction peaks at -1.2 and -2.6 V, which can be assigned to reduction of [Pt IV Br 6 ] 2- and [Pt II Br 4 ] 2- , respectively. The diffusion coefficients of the [Pt II Br 4 ] 2- and [Pt IV Br 6 ] 2- at 25°C were determined to be 1.5 × 10 -7 and 0.49 × 10 -7 cm 2 s -1 in BMPTFSA, respectively, by chronoamperometry. Electrodeposition of metallic platinum was possible by galvanostatic cathodic reduction on a glassy carbon electrode in BMPTFSA containing 10 mM [Pt II Br 4 ] 2- . In addition, platinum nano-particles (2-3 nm in diameter) formed and dispersed in the ionic liquid after potentiostatic cathodic reduction at -2.6 V. Platinum nano-particles could be collected by heating the ionic liquid containing the nano-particles with carbon black at 200°C. © 2013 The Electrochemical Society. All rights reserved.