Conventional polymer electrolyte membrane fuel cells often suffer from fuel crossover through the Nafion membrane and dehydration of the Nafion membrane at high current densities. Laminar flow-based fuel cells (LFFCs) exploit the advantage of laminar flow in microchannels, eliminating turbulent mixing between streams that merge in the same channel. In LFFCs, the anode and the cathode streams flow in parallel and their interface acts as a virtual membrane. Advantages of LFFCs include the ability to minimize fuel crossover by adjusting the flow rates of the anode and the cathode streams. Here we will focus on the fuel flexibility of air-breathing LFFCs. We demonstrate the operation of LFFCs with formic acid, methanol, hydrazine, sodium borohydride, and ethanol as the fuel. We will show the performance of LFFCs operating with alcohol-based fuels in acidic as well as alkaline media. Superior reaction kinetics, in particular for the oxygen reduction reaction is a key advantage of being able to operate in alkaline media. We have also investigated catalyst performance in microfluidic hydrogen fuel cells in which an acidic or alkaline stream is used as a flowing electrolyte. The cathode is typically the limiting electrode in H2/O2 fuel cells. In this presentation, we will compare hydrogen fuel cell performance using inexpensive non-Pt catalysts such as Ag-based cathodes instead of expensive Pt-catalysts with a flowing alkaline stream as the electrolyte. In alkaline media non-noble metal catalysts are more stable, and the rate of oxygen reduction is known to be enhanced. In summary, this presentation will illustrate the fuel and media flexibility of microfluidic fuel cells.

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