Mass transport enhancement in direct formic acid fuel cell with a novel channel design

Abstract

Direct formic acid fuel cells (DFAFCs) are a subtype of polymer electrolyte membrane fuel cells (PEMFCs) fed with liquid formic acid, which is an environmentally benign, low flammable chemical, with a higher volumetric energy density than compressed hydrogen, and can potentially be easily incorporated into the common gasoline infrastructure. Considering the laminar flow of formic acid in bipolar plate channels and the lower diffusivity of formic acid compared with gases, mass transport enhancement becomes crucial in improving the DFAFC performance. This study used computational fluid dynamics modeling to identify fuel starvation zones and uneven formic acid concentration distribution at the reaction surface in the DFAFC system with a standard channel design with serpentine arrangement. A new channel design (with right-angled trapezoidal baffles) was proposed based on the numerical simulations of hydrodynamic conditions at the anode side for various formic acid flow rates. This design enhances the uniformity in formic acid concentration distribution at the reaction surface and increases the convective fluxes between the neighboring channels in the serpentine arrangement. It was experimentally confirmed that the maximum power density of the DFAFC significantly increased for the proposed design compared with results of previous studies on hydrogen PEMFCs; an increase of 711.11 % was observed for the flow of 1 ml⋅min−1 of 9.0 M formic acid. This work underlines the advantage of CFD modeling in prototyping a new fuel cell channel design to enhance mass transport to the reaction surface and decrease concentration polarization.