Performance Characteriztion and Modeling of a Passive Direct Methanol Fuel Cell (DMFC) over a Range of Operating Temperatures and Relative Humidities

As the world begins to focus more and more on new and more effective means of energy production, fuel cells become increasingly more popular. While different fuel cells are already found in industry today, the direct methanol fuel cell (DMFC) is becoming an increasingly more probable means for portable power production. In such applications a passive air breathing direct methanol fuel cell would be ideal. However, successful use of the passive DMFC in such applications requires that the fuel cell be capable of operating at various temperatures and relative humidities. A passive air breathing direct methanol fuel cell was developed and manufactured for this study. This work studied the effects of varying relative humidity and temperature over a probable range of operating conditions for small scale portable power applications on the performance of the fuel cell, both in relation to power production and fuel consumption. Potentiostatic, electrochemical impedance spectroscopy, and polarization tests were performed in order to characterize the performance of the fuel cell. Additionally, a one dimensional steady state isothermal mass transport model was developed to provide insight to the behavior of the fuel cell. The experimental data and model results show that increasing the fuel cell temperature and decreasing the ambient relative humidity increases the current production capabilities of the fuel cell. Further, the experimental data suggests that the major problem hindering current production in passive air breathing direct methanol fuel cells is flooding of the cathode diffusion layer.