Estudos cinéticos em líquidos iônicos análogos utilizando uma poderosa ferramenta: voltametria semi-integral

The use of ionic liquids analogues, e.g. deep eutectic solvents (DESs), have attracted great attention over the last decades mainly because they might be promising candidates to replace typical room-temperature ionic liquids (RTILs) which maybe toxic and environmentally unfriendly. Besides several applications of DESs, the electrochemical studies involving these solvents play an important role for future applications, and some of their properties such as limited conductivity and high viscosity could compromise the results obtained by classical techniques, e.g. cyclic and linear voltammetry [1]. In this work, it is successfully shown the utilization of semi-integral approach for voltammetric analysis in ionic liquids analogues. The studies have been performed at glassy carbon electrode in glyceline (2Glycerol:1Choline Chloride) DESs containing FeCl3 at concentrations ranging 5 mM and 500 mM. The influence of temperature has also been evaluated (30 to 70°C). Fig. 1A depicts the cyclic voltammograms obtained at various concentrations of FeCl3 and shows an increase in the ΔEp as the [FeCl3] increases. This behavior is related to the reduction on the ratio of electroactive species: supporting electrolyte causes an ohmic effect in the voltammetric response that makes difficult the achievement of precise values of the diffusion coefficient (D) and charge transfer rate constant (k0) by the classical Nicholson and Shain method [2]. The semi-integrative voltammograms can be noted in Fig. 1B where is possible to obtain D, k0 and α (charge transfer coefficient) values separately [3]. Fig. 1B,normalized semi-integrated voltammograms, shows the variation of ML (limited semi-integrated current) as a function of [FeCl3] that is supported by the conductivity drop from 0.2 M to 0.5M FeCl3 observed in Fig 1C.