The influence of gas diffusion layer wettability on direct methanol fuel cell performance: A combined local current distribution and high resolution neutron radiography study

The influence of the anode and cathode GDL wettability on the current and media distribution was studied using combined in situ high resolution neutron radiography and locally resolved current distribution measurements. MEAs were prepared by vertically splitting either the anode or cathode carbon cloth into a less hydrophobic part (untreated carbon cloth ‘as received’) and a more hydrophobic part (carbon cloth impregnated by PTFE dispersion). Both parts were placed side by side to obtain a complete electrode and hot-pressed with a Nafion membrane. MEAs with partitioned anode carbon cloth revealed no difference between the untreated and the hydrophobised part of the cell concerning the fluid and current distribution. The power generation of both parts was almost equal and the cell performance was similar to that of an undivided MEA (110 mW cm−2, 300 mA cm−2, 70 °C). In contrast, MEAs with partitioned cathode carbon cloth showed a better performance for the hydrophobised part, which contributed to about 60% of the overall power generation. This is explained by facilitated oxygen transport especially in the hydrophobised part of the cathode gas diffusion layer. At an average current density of 300 mA cm−2, a pronounced flooding of the cathode flow field channels adjacent to the untreated part of GDL led to a further loss of performance in this part of the cell. The low power density of the untreated part caused a significant loss of cell performance, which amounted to less than 40 mW cm−2 (at 300 mA cm−2).