Electrode reactions of platinum bromide complexes in an amide-type ionic liquid

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^IIBr₄]^2- and [Pt^IVBr ₆]^2-, respectively. The cyclic voltammogram in BMPTFSA containing 10 mM [Pt^IVBr₆]^2- showed two reduction peaks at -1.2 and -2.6 V, which can be assigned to reduction of [Pt^IVBr₆]^2- and [Pt^IIBr ₄]^2-, respectively. The diffusion coefficients of the [Pt^IIBr₄]^2- and [Pt^IVBr ₆]^2- at 25°C were determined to be 1.5 × 10 ^-7 and 0.49 × 10^-7 cm² 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^IIBr₄] ^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.