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A single-phase model for liquid-feed DMFCs with non-Tafel kinetics
Authors:Marcos Vera
Affiliation:Área de Mecánica de Fluidos, Universidad Carlos III de Madrid, Avda. de la Universidad 30, 28911 Leganés, Spain
Abstract:An isothermal single-phase 3D/1D model for liquid-feed direct methanol fuel cells (DMFC) is presented. Three-dimensional (3D) mass, momentum and species transport in the anode channels and gas diffusion layer is modeled using a commercial, finite-volume based, computational fluid dynamics (CFD) software complemented with user supplied subroutines. The 3D model is locally coupled to a one-dimensional (1D) model accounting for the electrochemical reactions in both the anode and the cathode, which provides a physically sound boundary condition for the velocity and methanol concentration fields at the anode gas diffusion layer/catalyst interface. The 1D model – comprising the membrane–electrode assembly, cathode gas diffusion layer, and cathode channel – assumes non-Tafel kinetics to describe the complex kinetics of the multi-step methanol oxidation reaction at the anode, and accounts for the mixed potential associated with methanol crossover, induced both by diffusion and electro-osmotic drag. Polarization curves computed for various methanol feed concentrations, temperatures, and methanol feed velocities show good agreement with recent experimental results. The spatial distribution of methanol in the anode channels, together with the distributions of current density, methanol crossover and fuel utilization at the anode catalyst layer, are also presented for different opperating conditions.
Keywords:Fuel cell  Methanol  Non-Tafel kinetics  Crossover  CFD  Modeling
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