Microfluidic fuel cell with arc-shaped electrodes to adapt to its mixing zone, a simulation study

Fuel cells are well known for their uninterrupted power supply, high energy density, and environmental friendliness. Among them there is an emerging type for portable applications called microfluidic fuel cell (MFC), which has caught attention during the last twenty years. An MFC generally employs two electrolytes, namely the anolyte containing fuel and the catholyte containing oxidant, which flow in parallel inside a microchannel. In the middle, a narrow mixing zone is formed which has a typical cross section of hourglass shape. To better utilize this specific shape, an MFC with innovative arc-shaped electrodes is proposed in this work and validated via numerical simulation. The protruding electrode surface towards the channel middle can not only better utilize the limited channel space for more reaction sites, but also reshape the mixing layer to further prevent reactant crossover. Benefited from the enhanced convective transport as well as diffusive transport, the maximum power density with electrode radius of 2 mm is improved by 18.9% at the flow rate of 1000 mu L/min and 20.7% at the flow rate of 100 mu L/min, compared with conventional flat electrodes. Besides, the fuel utilization at 0.8 V is also improved by 30.4% at 1000 mu L/min and 32.6% at 100 mu L/min. This work provides a brand-new idea of optimizing the shape of MFC electrode, which can improve MFC performance indexes of both power density and fuel utilization at the same time.