ortho-Dichlorobenzene as a pore modifier for PEMFC catalyst electrodes and dense Nafion membranes with one porous surface

Abstract

ortho-Dichlorobenzene (ODB) was investigated as a pore modifier for both Nafion membranes and proton exchange membrane fuel cell (PEMFC) catalyst layers. When ODB containing Nafion dispersions are cast into a film, evaporation leads to dense membranes with one highly porous surface layer occupying 20-30% of the overall thickness. Dense Nafion membranes with a porous top layer are interesting for use in membrane humidifiers, for increasing the electrode-membrane interface areas in electrochemical devices like fuel cells or electrolysers, and other applications. Fuel cell membrane electrode assemblies were obtained by spray coating commercial Nafion 212 membranes with ODB containing catalyst inks. ODB does not poison the catalyst, and 54-120% higher potentials in comparison to the 217 mV obtained with an ODB free ink were achieved at 1.5 stoic air flow, 100% rh and a current density of 1 A cm(-2). This shows that the porous catalyst electrode structure is changed, resulting in a reduced contribution of mass transport limited overpotentials. Furthermore, MEAs prepared with ODB in the catalyst ink are less sensitive towards changes in the air flow rate and the cathode relative humidity (between 50% rh and 100% rh: 217-292 mV at 1 A cm(-2) without ODB and 439-478 mV with ODB).