Can Dicyanamide Ionic Liquids Boost Water Electrolysis?

Abstract

Room-temperature ionic liquids (RTILs) have attracted attention in engineering electrolytes for electrochemical energy conversion and storage devices. Within the present study, five different RTILs were prepared and subsequently investigated as additives to alkaline aqueous solutions for the oxygen evolution reaction (OER). Studied RTILs were based on dicyanamide ion as a green anion, suitable for electrochemical applications, and included 1-butyl-3-ethylimidazolium dicyanamide, 1,3-dibutylimidazolium dicyanamide, 1-butyl-3-hexylimidazolium dicyanamide, 1-butyl-3-octylimidazolium dicyanamide, and 1,3-diethylimidazolium dicyanamide. The OER studies were performed in 8 M KOH with RTILs (1 vol.%) using linear scan voltammetry, and the current densities were compared to those recorded in 8 M KOH with no RTILs added. Reaction parameters, such as the Tafel slope, were determined, enabling further evaluation and comparison of RTIL-containing electrolyte systems. Moreover, the influence of temperature on the OER efficiency of the system with mixed RTIL-KOH electrolytes was studied. Voltammetric studies were complemented by electrochemical impedance spectroscopy, which revealed a decrease in solution resistance with increasing temperature, as well as by chronoamperometry analysis.