Flow Field Effect on the Performance of Direct Formic Acid Membraneless Fuel Cells: A Numerical Study

The performance of both air-breathing and air-feeding direct formic acid membraneless fuel cells (DFAMFCs) possessing different flow fields were numerically investigated in this study at given concentration and flow rate for both fuel and electrolyte. Single serpentine, stepwise broadening serpentine, multi-serpentine and parallel channel were tested as liquid flow field, while single serpentine, stepwise broadening serpentine, multi-serpentine and pin channel were tested as air flow field. The channel width was either 0.8 mm or 1.3 mm. The simulation results showed that the air-breathing DFAMFC having identical flow field for both fuel and electrolyte yielded highest cell output. The air-breathing DFAMFC having SBS liquid flow field yielded a maximum power density of 10.5 mW/cm2, while the air-breathing DFAMFC having S(1.3) liquid flow field produced an open circuit voltage of 1.0 V owing to few formic acid penetration into the cathode. Concerning the air-feeding DFAMFCs, the DFAMFC having SBS liquid flow field and MS(0.8) air flow field yielded highest peak power density, 12 mW/cm2, at an airflow rate of 500 sccm. Considering the power generated by the DFAMFCs together with the power consumed by the air pump, DFAMFC having SBS liquid flow field and Pin(0.8) air flow field could be the preferred design.