Toward the scaling up of microfluidic fuel cells, investigation and optimization of the aggravated cathode flooding problem

The scaling up of microfluidic fuel cells (MFC) with enlarged electrode areas can be very advantageous for their power output and further stacking, which may, however, aggravate the cathode flooding problem due to intensified fuel crossover. In this paper, we first validate this phenomenon in a scaled-up MFC prototype, which has a hydrogen-breathing anode and an air-breathing cathode. Possible influential factors on the flooding extent are studied next, including the electrode area, electrolyte flow rate, and ambient temperature. Furthermore, three different strategies are proposed to improve cathode flooding, which is achieved either by adding an interlayer inside the channel to suppress hydrogen crossover, by adding hydrophilic water remover on the cathode surface to wick the generated water, or by cracking the cathode catalyst layer (CL) to manipulate the water transport direction. Among all these methods, the cracking of cathode CL is found to be remarkably effective especially with acid electrolyte, which exhibits the lowest current density degradation rate of 1.3 mA cm⁻² h⁻¹ when discharged at the peak power point for five hours.