Study of crossover and depletion effects in laminar flow-based fuel cells using electrochemical impedance spectroscopy

The impedance characteristics of the laminar flow-based fuel cells (LFFCs), which are also called microfluidic fuel cells (MFFCs), are measured to study the crossover and depletion phenomena. To study the effect of the crossover and depletion separately, the impedances are measured at different flow rates simulating different crossover conditions; while the effect of depletion is controlled by keeping the current density constant through changing the fuel concentration at different flow rates. Then the depletion effect is studied by measuring the impedance characteristics of the cell at various fuel concentrations. It is shown that the crossover affects the moderate frequency ranges in the measured Nyquist plot; whereas depletion impacts the low frequency domain. Finally, the impedance measurements at various potentials suggest that increasing the current density increases the effect of crossover while decreases the effect of depletion. This could be the result of carbon dioxide production in the anode.