Performance optimization of Direct Methanol Fuel Cell

Direct Methanol Fuel Cells (DMFCs) sustain an electrochemical reaction which converts the chemical energy stored in methanol directly into electricity. The main challenge in DMFC technology is that during the reaction, methanol crosses through the nafion membrane, i.e. from the anode to the cathode side, causing losses in electrical potential that leads to lower power output and inefficient fuel consumption. The main goal of the present work is to determine the optimal membrane thickness and operational temperature that will yield the highest current and power densities (CD and PD, respectively). To carry out this experiment, Membrane Electrode Assemblies (MEAs) with similar catalyst loadings and variable nafion membrane thicknesses of N117 (0.177 mm), N115 (0.127 mm) and N212 (0.076 mm) were purchased and utilized. A fuel cell with an active area of 50 cm² was assembled and connected to an electronic loading device to record output current, voltage and power. A temperature controlled system was used to set the cell temperature in the range from 20 °C to 70 °C, in 10 °C increments. It was found that at a temperature of 50 °C, MEAs containing N212 and N115 experienced a significant power increase; higher temperatures did provide higher power but were not as significant as the increase from 40 °C to 50 °C. It has also been observed that thinner membranes, at 50 °C and above, provided a greater PD and could achieve higher CD; N212 at 70 °C exceeded the PD and CD of all other tested MEAs. This is an indication that methanol crossover was not the main contributing parameter to power output, as originally thought. The benefits of reaction kinematics at elevated temperatures must have overcome the effects of excess crossover. N212 at 70 °C achieved the highest performance.