Oxygen electroreduction in perfluorinated sulphonyl imides

Abstract

The electroreduction of oxygen in perfluorinated sulphonyl imides has been studied with the emphasis on the identification of alternate acid electrolytes which could replace the presently used phosphoric acid as an electrolyte in H₂−O₂ fuel cells. The activity for oxygen reduction on smooth platinum and gas-fed, high surface area platinum-catalysed electrodes (10% platinum loading on XC-72 carbon support) has been examined. The polarization of the air cathode in the micro-fuel cell in bis(trifluoromethanesulphonyl)imide is 40 mV more positive compared to phosphoric acid at 100 mA cm⁻², presumably due to the increased solubility of oxygen and lower tendency of bis(trifluoromethanesulphonyl)imide to adsorb on the platinum catalyst. The related bis(fluorosulphonyl)imide is unstable in water and the hydrolysis products adsorb strongly on the catalytic sites, resulting in poor performance.