Ionic liquids as electrolytes in PEFCs for operating temperatures of around 120 °C
The elevated operating temperature of polymer electrolyte fuel cells (PEFCs) is particularly advantageous for applications in the field of electromobility. Since there is no liquid water, a complex water management system is not required, and the fuel cell system is more compact, lighter, and cheaper. The more effective cooling at higher temperatures also contributes to this. Furthermore, the noble metal catalysts are also more tolerant of impurities in the gases being supplied, which cuts gas purification costs. However, at operating temperatures above 100 °C, thermally stable membrane materials or electrolytes are required that are conductive without the need for liquid water. Strongly acidic, proton-conducting ionic liquids (PILs), which are used to dope polymer membranes, are promising candidates. Important membrane properties such as proton conductivity and thermal stability need to be studied in detail. This also applies to oxygen reduction reaction (ORR) kinetics at the platinum catalyst of the fuel cell cathode in contact with PILs and the double layer capacitance at the platinum/PIL interface. Precise knowledge of this will allow for selective improvement of the PIL properties with regard to the ORR rate, and thus of the entire fuel cell.