Electrochemical, Thermodynamic and Spectroscopic Investigations of Ce III in a 1‐Ethyl‐3‐methylimidazolium Ethyl Sulfate (EMIES) Ionic Liquid

A systematic study was carried out to explore the electrochemical behaviour of Ce in an EMIES ionic liquid at a glassy carbon (GC) electrode over the range 298–351 K. The electrode reaction of Ce III /Ce IV was found to be quasi‐reversible by cyclic voltammetry. An increase in the current intensity was obtained with an increase in temperature. The diffusion coefficients ( D o ), the transfer coefficients ( α ) of Ce III and the charge‐transfer rate constants ( k s ) were estimated. The apparent standard potential ( E 0 *) and the thermodynamic properties of the oxidation of Ce III to Ce IV were also investigated. A photoluminescence investigation on cerium extracted in EMIES ionic liquid shows the stabilization of cerium in the Ce III state. There is a broad band at 350 nm, which is attributed to the 5d 1 →4f 1 transitions. With an increase in temperature the Ce III peak intensity decreases gradually and is almost flattened at 350 K. This may be a result of Ce III being converted into Ce IV with an increase in temperature and then not being luminescence‐active as it is an f 0 system.