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 halides were dissolved in BMPTFSA with addition of halide salts of BMP+. Ultraviolet and visible absorption spectra of electrolytes revealed that the coordination environment of Pt(II) and Pt(IV) were [PtBr4](2-) and [PtBr6](2-), respectively. The cyclic voltammogram in BMPTFSA containing 10 mM [PtBr6](2-) showed two reduction peaks at -1.2 V and -2.6 V. The diffusion coefficients of the [PtBr4](2-) and [PtBr6](2-) were calculated to be 1.5 x 10(-7) and 0.49 x 10(-7) cm(2) s(-1) in BMPTFSA, respectively, by chronoamperometry. Electrodeposition of platinum in BMPTFSA containing 10 mM [PtBr4](2-) was attempted by potentiostatic cathodic reduction at -2.6 V. Nano-particles (2-3 nm in diameter) in the electrolyte after potentiostatic cathodic reduction were observed by transmission electron microscopy. The nano-particles were found to be metallic platinum by electron diffraction.