Ultramicroelectrode Voltammetry and Scanning Electrochemical Microscopy in Room Temperature Ionic Liquids

Abstract

This year (2014) marks the 25th anniversary of the invention of SECM in the Bard lab at the University of Texas [1,2]. Such is the impact of its development that the scanning electrochemical microscope (SECM-the same abbreviation is used for the instrument and the method) is now a "textbook" electroanalytical tool used in a wide variety of applications, ranging from fundamental studies of mass and charge transfer dynamics to molecular transport across biological cell membranes, corrosion analysis and electrocatalyst screening [3,4]. Given the increasing popularity of room-temperature ionic liquids (RTILs) in electrochemical studies and devices [5,6], it was perhaps inevitable that SECM measurements would also be carried out in RTILs and a number of such studies have appeared in the recent literature [7][8][9][10]. However, the unique physicochemical properties of RTILs can lead to very unusual behaviour being observed during SECM. For example, drastic differences in the rates of diffusion of charged and uncharged species can arise in RTILs and such phenomena have been studied using SECM [11]. The high viscosities of RTILs also mean that unusual SECM responses are often obtained in RTILs, unless one carefully controls the experimental parameters [9].In this chapter, those studies that have involved performing SECM in RTILs will be discussed. As we will see, a relatively small number of such studies have been carried out to date, but unique electrochemical insights have been obtained. In attempting to fully describe how the properties of RTILs affect SECM in these media, the voltammetric behaviour of UMEs must also be described as the operation of the SECM depends on the behaviour of UMEs during electrolytic reactions. The chapter begins with a brief description of the principles of UME voltammetry and

Understanding the Role of Protic Ionic Liquids (PILs) in Reactive Systems: Rational Selection of PILs for the Design of Green Synthesis Strategies for Allylic Amines and β‐Amino Esters

“…For EAN, the CVs (shown in Figure a) were measured at different scan rates and over varied potential intervals. The cathodic discharge of hydrogen from free nitric acid is verified in the cathodic scan at E < −0.5 V. The attainment of a voltammetric peak whose current magnitude depends on the scan rate indicates that this process is controlled by the low mass transport rate of nitric acid in this medium . Upon extending the potential range to more cathodic values (inset graph), a second reduction current increment is detected at E<−1.2 V (also shown in previous reports for EAN and for other PILs), which is probably caused by the reduction of ethylammonium.…”