Electrochemical Behavior of Vitreous Glass Carbon and Platinum Electrodes in the Ionic Liquid 1-n-Butyl-3-Methylimidazolium Trifluoroacetate

Abstract

A janela eletroquímica do líquido iônico trifluoroacetato de 1-n-butil-3-metilimidazólio foi estudada sobre eletrodos de carbono vítreo e platina em condições estática e dinâmica. Observouse uma drástica diminuição da janela eletroquímica ao trocar o eletrodo de carbono vítreo (4.50 V) pelo de platina (2.50 V). A variação da velocidade de rotação do eletrodo e da velocidade de varredura não afetaram o perfil dos voltamogramas, porém alteraram as densidades de corrente dos picos referentes aos processos anódicos e catódicos. A adsorção do cátion imidazólio durante o processo de transferência de carga na região catódica foi evidenciada, principalmente para baixas velocidades de rotação do eletrodo.The 1-n-butyl-3-methylimidazolium trifluoroacetate ionic liquid electrochemical windows have been investigated at vitreous carbon and platinum disc electrodes under static and dynamic conditions. The electrochemical window abruptly decreases by changing vitreous carbon (4.50 V) by platinum electrode (2.50 V). Electrode rotation and potential sweep rate did not affect the current-potential profiles but alter the current values of both anodic and cathodic peaks. The adsorption of imidazolium cation involved in the charge transfer process during the cathodic sweep rate was evidenced, mainly at low electrode rotation.Keywords: platinum electrode, vitreous carbon electrode, ionic liquid, imidazolium cation IntroductionRoom temperature molten salts or ionic liquids have been historically considered as liquid electrolytes composed entirely of ions. However, new evidences in the last years pointed out that these compounds, specially those based upon N,N'-dialkyl substituted imidazolium cations, are better described as liquid compounds that display ioniccovalent structures.1 In the light of their promising physical and chemical properties, room temperature ionic liquid systems attract increasing attention for applications as solvents in organic synthesis, transition metal two-phase catalysis, liquid-liquid extraction and electrochemical devices.1-3 Some characteristics that make these liquids so versatile and promising as novel solvents are (i) the high thermal stability and wide range of liquid phase, 4 (ii) their ability to act as solvents for many organic and inorganic materials, since it has been shown that they have micro heterogeneities that induce to act either as highly or weakly polar liquids, 5 (iii) the considerable conductivity, which commends their use in the study of electrochemical processes without using supporting electrolytes, and (iv) the negligible vapor pressure in contrast with conventional organic solvents, permitting their study under conditions of high vacuum. From the ecological point of view, the easier recovery of these solvents and its negligible vapor pressure, which avoid vapor emissions, makes these solvents environmental friendly. 1We have recently showed that the ionic liquids obtained from the combination of 1-n-butyl-3-methylimidazolium cation with tetrafluoroborate and hexafluorophosphate are ...

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