Electrodeposition of platinum in room-temperature ionic liquids and electrocatalytic effect on electro-oxidation of methanol

The use of room-temperature ionic liquids (RTILs) as green media for electrochemical application is desirable. The electrodeposition behavior of platinum was investigated at a glassy carbon electrode in hydrophilic 1-n-butyl-3-methylimidazolium tetrafluoroborate (BMIMBF4) and hydrophobic 1-n-butyl-3-methylimidazolium hexafluorophosphate (BMIMPF6) RTILs containing chloroplatinic acid hexahydrate by cyclic voltammetric and potentiostatic transient techniques and atomic force microscopy (AFM). For comparison, the electrodeposition of platinum in HClO4 aqueous solution was also investigated. The cyclic voltammograms after the first scan circle in these media were different from each other, showing the obvious media effect on the electrochemical behavior of chloroplatinic acid hexahydrate. The analysis of the experimental current transients showed that the electrodeposition process of platinum in these media was characteristic of three-dimensional progressive nucleation with diffusion-controlled hemispherical growth. AFM showed that the uniform, shiny electrodeposits of platinum obtained in BMIMBF4 and BMIMPF6 RTILs were fairly dense and that the separate spherical nanoclusters were less than 100 nm. For the electro-oxidation of methanol in H2SO4 solution, the platinum films prepared in both BMIMBF4 and BMIMPF6 RTILs exhibited high electrocatalytic current densities. (c) 2005 The Electrochemical Society.