Pore-scale modeling of mass transport in the air-breathing cathode of membraneless microfluidic fuel cells

The air-breathing cathode of membraneless microfluidic fuel cells (MMFCs) is in direct contact with flowing aqueous electrolyte rather than a solid polymer membrane, suggesting the mass transport characteristics can be different from the air-cathode in conventional membrane-based fuel cells. To investigate the mass transfer and reaction, pore-scale Lattice Boltzmann (LB) models were developed for the air-breathing cathode, including the gas diffusion layer (GDL), the catalyst layer and the electrolyte microchannel. A modified multi-relaxation-time LB model was developed to handle the very large diffusivity ratio (10(4)) between gaseous and dissolved oxygen. The GDLs were numerically reconstructed to mimic the real microstructure. The effect of GDL property (porosity, isotropy) and operation conditions (overpotential, electrolyte flow rate) were investigated and discussed. The results indicated that the GDL microstructure played an important role for the oxygen transport and reaction in the air-breathing cathode. Oxygen was found to penetrate the electrolyte microchannel and could form a thin layer of dissolved oxygen covering the catalyst layer, which in-turn affected oxygen transfer in the GDL. The electrolyte flow can also affect local oxygen transport but only showed minimum impacts. (c) 2022 Elsevier Ltd. All rights reserved.

Automated summary

In this study, pore-scale Lattice Boltzmann models were developed to investigate the air-breathing cathode of membraneless microfluidic fuel cells. The results indicated that the microstructure of the gas diffusion layer played a crucial role in oxygen transport and reaction, while the electrolyte flow rate showed minimal impacts.