The impact of bromide-based ionic liquids on alkaline water electrolysis

Abstract

Two bromide-based ionic liquids, l-butyl-3-ethylimidazolium bromide [Beim][Br] and 1, 3-diethylimidazolium bromide [Eeim][Br], were prepared and their effect as alkaline electrolyte additives investigated for the hydrogen evolution reaction (HER). The addition of 2 vol.% of [Beim][Br] led to higher current densities. The bromide-based additives changed the HER kinetics, with slightly higher Tafel slopes, small effects on the charge transfer coefficient and a decrease of the exchange current density being among the observed effects. Impedance measurements showed a strong decrease of the overall impedance of the system in the ionic liquid-added alkaline electrolytes, with the Nyquist plots being dominated by the intermediate frequency relaxation related with the adsorbed H. The results show the ability of the bromide-based ionic liquids to improve the electrolyte properties and to lead to better alkaline electrolysis performances.