Role of Binders in High Temperature PEMFC Electrode

Several different binders for high temperature proton exchange membrane fuel cell (PEMFC) were tested to investigate the effects of binder properties on cell performance. The cell voltage values measured with electrodes with PTFE binders are compared to that obtained with electrode with PBI or polyurethane binders. The electrodes that used PBI and polyurethane binders showed Tafel slopes of 87 mV/decade, and the values were lower than the Tafel slope measured from Teflon containing electrodes which showed the Tafel slope value of 100 mV/decade. Pt utilization also showed dependence on the kind of binders used in the electrodes. When PTFE or polyurethane binder was used, Pt utilization of 15% was measured. The PBI binder was found to reduce Pt utilization, and 10% of catalyst utilization was measured. The changes in Tafel slope, Pt utilization, η_ohm affected cell performance, and it was found that the electrodes with polyurethane binder showed the highest cell voltage among the tested binders with the cell voltage of 0.619V @ 0.2 A/cm₂. Binder properties also affected cell life time. By increasing Teflon content in the electrode, it was possible to operate cells for a longer period.