Kunihiro Nakato

Optimization of proton exchange membranes and the humidifying conditions to improve cell performance for polymer electrolyte fuel cells

The relationship between thickness of the proton exchange membrane and cell performance was measured. Use of cells with thinner membrane resulted in an apparent reduction in the volume of water transferred from the anode to the cathode, offering stable cell performance even under conditions of low-humid reaction gas supplied. Internal humidification, with its constant feeding of sufficient water to the anode, was found to provide an equivalent of the external humidification process, without needing humid air. On the basis of these findings, a fuel cell module was assembled featuring newly designed gas separators to feed water directly to the fuel flow field in the cells. The fuel cell module was then submitted to module performance testing under a broad spectrum of operating conditions and it demonstrated performance stability against load variations from startups at room temperature to operations under the rated load.