Experimental study on the effect of new anode flow field designs on the performance of direct methanol fuel cells

Enhancing the performance of direct methanol fuel cells (DMFCs) through developing novel designs of anode flow field is significant. Thus, three new anode flow field designs (design-2, design-3, and design-4) are developed. The proposed designs combined all the advantages of serpentine, multi-zone, tapering and zigzag patterns into specific flow fields. In addition to reducing the path length of the bubbles, they accelerate their removal from the flow channels. To assess the cell's performance, an experimental study was conducted to determine the effect of the new anode flow field designs along with methanol flowrates and methanol concentrations. Optical observations and electrochemical characterization methods are used to track the bubbles' behavior and measure the power density of the new fabricated transparent DMFC. Experimental measurements indicate that the new flow fields significantly boost the cell's performance at almost all operating conditions. A comparison between the output power of the new flow field designs and the reference serpentine design (design-1) showed that the new flow field designs attained a percentage enhancement of the maximum peak power density of 133%, 75 % and 103%, by design-2, -3 and -4, respectively. The highest limiting current density and peak power density achieved by the new designs were 566.5 mA/cm2 and 56.25 mW/cm2, respectively compared with the 257.25 mA/cm2 and 24.18 mW/cm2 of the reference design. Moreover, a general trend indicates that a 3.0 mol/L concentration performed the highest followed by 2.0 mol/L and finally, 1.0 mol/L. However, a lower methanol flowrate performed better than higher flowrate in the order of 2, 5 and 8 mL/min. The new designs are also able to evacuate the CO2 gas bubbles better than the reference design. The present findings encourage the fuel cell designers to critically think about enhancing the fuel cell performance via developing new flow field designs.