Internal reference redox scale

One of the open problems of electrochemistry in ionic liquids nowadays is the choice of a reference electrode. Chapter 3 discusses the latest understanding and practical approaches to the apphcation of reference electrodes and internal reference redox scales in ionic hquids. Problems and limitations of reference systems are presented with the help of experimental examples. Comparison of the behavior of internal reference redox systems in organic solvents with added supporting electrolyte and ionic hquids is provided and new observations critically discussed. This chapter is very important for any experimentalist starting work in the electrochemical and IL helds. Further information about internal reference redox scales can also be found in Volume 2 (Chap. 14). 

Internal reference redox scales or internal reference redox systems, IRRS, are reversible or nearly reversible redox systems used to provide a known and stable reference point in nonaqueous solvents in conditions where reliable reference electrodes are difficult to be established and/or stabilized [20], In general, IRRS is used in conjunction with a QRE [18,41—44],... 

Selection of an Internal Reference Redox Scale for Voltammetric Measurements... 

IRRS Internal reference redox systems/internal reference redox scale... 

One of the open problems of electrochemistry in ionic liquids (ILs) nowadays is the choice of a reference electrode. In order to carry out reliable electrochemical measurements in ILs, a robust and stable reference electrode is required. Unfortunately, many literature reports describe the use of poorly chosen, unreliable reference electrodes or the use of quasi-reference electrodes of unknown potential versus any standard potential scale, so they could not be reproduced, being therefore, of little or no value [1]. In addition, the potential differences of reliable reference electrodes in ILs have rarely been measured, preventing the comparison of potential data measured by different research groups in the same IL. A similar situation was reported by lUPAC almost 30 years ago for nonaqueous systems [2]. As a consequence, it is necessary to agree for ILs systems on some procedures and limitations to measure and report electrode potentials versus generally accepted standards. There are in general two possible ways (a) to use a reference electrode or (b) to refer aU potentials versus internal reference redox systems. 

The difference of 10 mV is significant since the ferrocene/ferrocenium redox couple is often used as a redox marker in non-aqueous electrochemistry (acting as an internal reference electrode), including that using room temperature ionic hquids as solvents. The correction for the difference in diffusion coefficients is necessary to give a valid reference scale. 

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