Modeling the Effects of Methanol Crossover on the DMFC

Abstract

A mathematic model is established to simulate the effects of methanol crossover on the DMFC. The transport and reactions of both oxygen and methanol at the cathode are described and the theory of “parallel electrode reactions” is applied to calculate the cathode over‐potential caused by methanol crossover. The influence of methanol concentration, fuel cell temperature, oxygen pressure, and membrane properties on the cathode over‐potential is evaluated. Simulation results show that methanol crossover considerably increases the cathode over‐potential at low current density, but its effect is significantly reduced when the current density is increased to reasonable values. It also shows that of the two parameters characterizing a polymer electrolyte membrane, proton conductivity and methanol permeability, the former has more impact on the performance of a DMFC.

Nanocomposite SPEEK-based membranes for Direct Methanol Fuel Cells at intermediate temperatures

“…Consequently, a simultaneous and equivalent increment of proton conductivity and methanol permeability would not cause any change on the DMFC performance. However, many authors have empirically demonstrated that proton conductivity is the main parameter governing the DMFC performance during standard operating conditions [33][34][35]. This is explained by the fact that methanol is electrochemically oxidized at the anode and, thereby, the driving force for methanol permeation, that is the concentration gradient, diminishes with increasing current density.…”

“…This is in agreement with the empirical evidence that DMFC performance is mainly governed by proton conductivity of the membrane. This is a consequence of methanol crossover to decrease with increasing current density, thus becoming ohmic losses the dominant parameter [33][34][35].…”

On the Methanol Permeability through Pristine Nafion® and Nafion/PVA Membranes Measured by Different Techniques. A Comparison of Methodologies

“…At higher current densities the results may differ as the electro-osmotic effect will become more significant while the gradient concentration will diminish due to the increased methanol consumption at the anode [23]. Generally, methanol transport across the membrane and methanol crossover over-potential at the cathode both decrease with increasing current density [23][24][25].…”

“…Generally, methanol transport across the membrane and methanol crossover over-potential at the cathode both decrease with increasing current density [23][24][25]. Thus, methanol permeability predominates at low current density (via over-potential losses at cathode) while proton conductivity predominates at high current density (via ohmic losses in membrane) on the DMFC performance [23]. In principle, neglecting mass transport phenomena in gas diffusion layers (GDLs), results obtained in situ at open circuit voltage (OCV) conditions, if CO 2 and unreacted methanol are analyzed, should be equivalent to those values measured by ex situ methods.…”

Synthesis and properties of a novel sulfonated poly(arylene ether ketone sulfone) membrane with a high β-value for direct methanol fuel cell applications

“…Direct methanol fuel cells (DMFCs) have attracted much interest, due to their advantages of compact size, high fuel efficiency, environment friendly, and high power density [1][2][3][4][5]. In a DMFC, methanol is oxidized at the anode to form protons, electrons, and carbon dioxide.…”