Sequential flow membraneless microfluidic fuel cell with porous electrodes

A novel convective flow fuel cell with porous electrodes is described. In this fuel cell design, the fuel (formic acid in sulfuric acid) flows radially outward through a thin disc anode and across a gap to a ring shaped cathode. The oxidant (potassium permanganate in sulfuric acid) is introduced into the gap and advects radially outward through the cathode. This fuel cell differs from previous designs in that the reactants flow in series rather than in parallel. The flow velocity field is examined using μPlV and shown to be nearly axisymmetric and steady. The results show that increasing the electrolyte concentration and flow rate reduce the cell Ohmic resistance and mass transport losses, resulting in larger peak power densities. An average open circuit potential of 1.2 V is obtained with maximum current and power densities of 5.35 mA cm^-2 and 2.8 mW cm^-2 respectively (cell electrode area of 4.3 cm^-2). At a flow rate of 100 μL min^-1 a fuel utilization of 58% is obtained.