Performance enhancement of phosphoric acid-based proton exchange membrane fuel cells by using ammonium trifluoromethanesulfonate

In a fuel cell system where concentrated phosphoric acid (PA) is used as a proton conducting medium, the use of PA causes some undesirable effects on oxygen reduction reaction (ORR) at Pt catalyst. Ammonium trifluoromethanesulfonate (ATFMS) is introduced as a cathode additive to increase the local oxygen concentration near the Pt catalyst. A cathode with the optimum composition of ATFMS shows a higher single cell performance than that without the additive when a single cell based on a PA-doped polymer membrane is operated at 150 degrees C. The enhanced ORR activity and oxygen solubility with the incorporation of ATFMS are proved with rotating disk electrode (RDE) and Pt microelectrode experiments. Single cell performance for longer than 600 h without decay in operating voltage could support the stability of the additive. (C) 2009 Elsevier B.V. All rights reserved.