Abstract
Abstract Most microfluidic fuel cells use highly soluble fuels and oxidants in streams of liquid electrolytes to overcome the mass transport limitations that result from the low solubility of gaseous reactants such as hydrogen and oxygen. In this work, we address these limitations by implementing controlled two-phase flows of these gases in a set of microchannels electrolytically connected through a narrow gap. Annular flows of the gases reshape the concentration boundary layer over the surface of electrodes and increase the mass-transport limited current density in the system. Our results show that the power density of a two-phase system with hydrogen and oxygen streams is an order of magnitude higher than that of single phase system consisting of liquid electrolytes saturated with the same reactants. The reactor design described here can be employed to boost the performance of MFFCs and put them in a more competitive position compared to membrane based fuel cells.
Highlights
Close to two centuries have passed since the first reports of hydrogen fuel cells [1]
The main purpose of this study is to mitigate the mass transport limitations in MFFCs, which arise from the low solubility of hydrogen and oxygen in liquid electrolytes
Mass transport models suggest that the maximum power density can be enhanced by up to a factor of 11 for a fuel/ oxidant flow rate of 16 ml hÀ1, when going from single phase to two-phase operation
Summary
Close to two centuries have passed since the first reports of hydrogen fuel cells [1] These interesting early power generators did not reach practical use until recently due to various technical, social, political, and economic reasons. Hydrogen fuel cell vehicles have regained attention, and are commercially available today [2,3]. Portable electronics is another sector with high potential for fuel cells, given the possibility of achieving higher power densities than batteries. Implementation in this sector requires the development of light weight and compact fuel cells. Their compatibility with semiconductor manufacturing processes makes micro fuel cells a promising power source for consumer electronics
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