Protic ionic liquids: Fuel cell applications

We have investigated protic ionic liquids (PILs) as proton conductors for non-humidified intermediate-temperature fuel cells. PILs exhibit proton conductivity and activity in fuel cell electrode reactions, as seen in acidic aqueous solutions and acidic polymer membranes. The wide molecular designability of PILs enabled the finding of a promising candidate, diethylmethylammonium trifluoromethanesulfonate ([dema][TfO]), which exhibits favorable bulk properties and electrochemical activity. Solid thin films containing [dema][TfO] were fabricated using sulfonated polyimide as a matrix polymer. By using the composite membrane, non-humidifying fuel cell operation at 120 degrees C succeeded. The fuel cell performance can be further improved by the optimization of the catalyst layer and with further research on PILs.