Electrochemistry of hydrogen evolution in ionic liquids aqueous mixtures

Use of room-temperature ionic liquids (RTILs) as electrolyte additives for highly efficient alkaline water electrolysis at low temperatures is evaluated. The hydrogen evolution reaction (HER) was studied with platinum cathode in 8 M KOH solution with and without addition of 2 vol.% of [Emim][MeSO3] in the 25–85 °C temperature range using voltammetry, chronoamperometry and electrochemical impedance spectroscopy measurements. Catalytic effect of IL’s presence in the electrolyte is evidenced for temperatures up to 45 °C by an increase of the exchange current density values, as well as a significant decrease of the overall impedance in the entire potential range. Thus, a lower activation energy of 38 kJ mol−1 is determined for HER in IL-added KOH compared to that of 48 kJ mol−1 for HER in IL-free KOH.