Progress on electrochemical preparation of inorganic materials in deep eutectic solvents-mediated organic electrolytes

Abstract

Excellent electrical conductivity, wide potential windows, high solubility, and low vapor pressure are typical of deep eutectic solvents, which endow these newly emerging solvents with significant advantages in electrochemical preparation. Deep eutectic solvents have proven effective for the electrochemical preparation of inorganic materials, either as complete electrolytes or as conductive mediators in electrolyte systems. The related technical route comprises electrodeposition, electro-exfoliation, and electrolytic redox, and the resultant materials have demonstrated impressive functional enhancements. This review begins with a concise overview of compositions, characteristics, and applications of the deep eutectic solvents. Whereafter, progress in electrochemically preparing inorganic materials in deep eutectic solvents-mediated organic electrolytes is retrospectively emphasized. The deep eutectic solvents discussed are limited to those derived from choline quaternary ammonium salts, especially Reline, Ethaline, and Glyceline. The synthesis includes electrodeposition to synthesize elementary substances, bimetallic alloys, trimetallic alloys, and metal-nonmetal compounds. The electrochemical process involves electro-exfoliation to produce two-dimensional materials, exemplified by graphene. The preparation also covers the electrolysis to prepare metallic oxides. Finally, the electrolytic preparation of functional inorganic materials in deep eutectic solvent-mediated organic electrolytes, based on two-electrode systems, is discussed and envisioned.