Rare-earth metals are considered critical metals due to their extensive use in energy-related applications such as wind turbines and nickel−metal hybrid batteries found in hybrid electrical vehicles. A key drawback of the current processing methods includes the generation of large amounts of toxic and radioactive waste. Thus the efficient recovery of these valuable metals as well as cleaner processing methods are becoming increasingly important.Here we report on a clean electrochemical route for neodymium (Nd) recovery from [P 6,6,6,14 ][TFSI], trihexyltetradecylphosphonium bis(trifluoromethylsulfonyl)amide which is amplified three times by the presence of water, as evidenced by the cathodic current density and thicker deposits. The role of Nd salt concentrations and water content as an additive in the electrochemistry of Nd 3+ in [P 6,6,6,14 ][TFSI] has been studied. The presence of metallic neodymium in the deposits has been confirmed by X-ray photoelectron spectroscopy.

The preparation and characterization of a series of ionic liquids based on S-alkyl thiolonium, S-alkyl thiotetrazolium, or S-alkyl thiobenzolium cations coupled with bis(trifluoromethanesulfonyl)amide, trifluoromethanesulfonate, alkyl phosphate, chloride, and hexafluorophosphate anions are reported. All are liquid at room temperature, except the chloride salt, which has a melting point of 92 degrees C. The electrochemical characteristics of this class of ionic liquid have been determined by cyclic voltammetry. Potential windows of the ionic liquids have been obtained at glassy carbon, platinum, and gold electrodes and found to be the largest at glassy carbon, but are limited by oxidation of the thioether-functionalized cation. The voltammetry of IUPAC reference potential scale systems, ferrocene/ferrocenium, cobaltocenium/cobaltocene, and decamethylferrocene/decamethylferrocenium have been evaluated, with the last being most widely applicable. Nonadditivity of Faradaic current is found in the voltammograms of decamethylferrocene in the presence of ferrocene and cobaltocenium. Diffusion coefficient, viscosity, ionic conductivity, double layer capacitance, and other physical properties have also been measured. The dependence of the diffusion coefficient vs viscosity follows the Stokes-Einstein relationship. The properties of the ionic liquids are compared with the related imidazolium family of ionic liquids.

An attractive couple: (Pro2H+)2(TCNQ.−)2⋅TCNQ (TCNQ=tetracyanoquinodimethane) contains an H‐bonding network that supports a layered structure, composed of alternating TCNQ anions and proline cations (see picture). The cation is formed by two zwitterionic proline amino acids supported by a proton bridge between the carboxylates, whereas the anionic component involves a neutral TCNQ molecule sandwiched between two TCNQ.−.