Enhancing the Performance of Direct Methanol Fuel Cells Using New Cathode Flow Field Designs: an Experimental Investigation

To improve the performance of the cell in terms of current density, power density and byproduct water removal from the cathode, three new cathode flow fields are designed, fabricated and tested. Design -1 is a conventional serpentine with a channel width and rib width of 0.8 mm. Design -2 is a -four outlet, and one inlet -four zone serpentine with a channel width and rib width of 0.8 mm. Design -3 is a four outlet -one inlet four zone serpentine with a gradually reducing channel width from 1.5 mm at the inlet to 0.8 mm at the four outlets. Design -4 is a four outlet -one inlet four zone zigzag serpentine with a gradually reducing channel width from 1.5 mm at the inlet in the middle to 0.8 mm at the four outlets. The open angle of 0.16 degrees is used in design -3 and design -4. All the designs cover a 50 mm x 50 mm area with open ratios in the range 48.9%-50.0%. To assess the cell's performance, an experimental study is conducted to determine the effect of the new cathode flow field design along with methanol flow rates and methanol concentrations. Electrochemical characterization methods are used to measure the power density of the new fabricated transparent DMFC. Results indicate that the highest recorded limiting current density and peak power density by the experiment are 460 mA/cm2 and 50 mW/cm2 respectively. The reference design using a conventional serpentine flow field attains a current density of 257 mA/cm2 and power density of 24 mW/cm2. Comparing new cathode designs with the reference one, the enhancement percentage in terms of the maximum peak power density by design -2, -3 and -4 are 44%, 107% and 22%, respectively. The lower anode flowrates outperforms the higher flowrates. The byproduct water at the cathode was better removed by the new cathode designs compared to the reference design. This research provides leeway for researchers to enhance the performance of DMFCs via new cathode flow fields.