Diethylmethylammonium trifluoromethanesulfonate protic ionic liquid electrolytes for water electrolysis

摘要

Protic ionic liquids (PILs) are promising electrolytes for electrochemical devices, owing to their wide electrochemical stability, good ionic conductivity, low vapour pressure and good thermal stability. In this study, we demonstrate that [Dema-H](+) [TfO](-) can be used as an electrolyte for intermediate temperature water electrolysis. The cyclic voltammograms of [Dema-H](+) [TfO](- )on Pt show a potential window of 2.5 V which is beyond water decomposition potential of 1.23 V. Two hydrogen evolution reactions are observed on Pt electrode in both "as prepared" [Dema-H](+) [TfO](-) and 10% [Dema-H](+) [TfO](-) in water. The first HER involving H3O+ had a peak potential at -0.255 V (vs SHE with limiting current density of 0.016 mA/cm(2) assigned to Pt low surface coverage/adsorption of H+/H3O+. The second HER involving [Dema-H] + had an on-set at -0.475 V vs SHE and did not show limiting current up to 0.1 mA cm(-2) (-0.8 V vs. SHE). Second observed HER is believed to be due to reduction of two [Dema-H] + to produce H-2 and diethyl methyl amine [Dema]. The latter is reoxidised at anode to reproduce [Dema-H](+). In-situ mass spectrometric analysis confirmed H-2/O-2 evolution at both potentials. The oxygen evolution reaction (OER) on IrO2 in 10% [Dema-H](+) [TfO](-) also shows two onset potentials.