Hydrogen production by water electrolysis using tetra-alkyl-ammonium-sulfonic acid ionic liquid electrolytes

Triethylammonium–propanesulfonic acid tetrafluoroborate (TEA–PS·BF4) is used as an electrolyte in the water electrolysis. The electrolysis of water with this ionic conductor produces high current densities with high efficiencies, even at room temperatures. A system using TEA–PS·BF4 in an electrochemical cell with platinum electrodes has current densities (i) up to 1.77 A cm−2 and efficiencies between 93 and 99% in temperatures ranging from 25 °C to 80 °C. The activation energy observed with TEA–PS·BF4 is ca. 9.3 kJ mol−1, a low value that can be explained by the facilitation of proton transport in the organised aqueous ionic liquid media. The unexpectedly high efficiency of this system is discussed by taking into account the high conductivities associated with the Brönsted and Lewis acidity characteristics associated with these ionic conductive materials.