Water Management for μ DMFC with Foamed Stainless Steel Cathode Current Collector.

For micro direct methanol fuel cell ( μ DMFC), water flooding on the cathode seriously affects the performance stability. Additionally, the effect of material and wettability of the cathode current collector (CCC) on the drainage capacity is studied to improve the μ DMFC's performance. To this end, a CCC with foamed stainless steel was prepared to assemble the μ DMFC due to its absorbency. Further, based on analyzing the gas-liquid two-phase flow characteristics of the μ DMFC cathode, it was found that the gradient wettability CCC could accelerate the discharge of cathode water. Hence, the foam stainless steel CCC was partially immersed in a KOH solution to complete the gradient corrosion using its capillary force. Then, four different types of gradient wettability CCC were prepared by controlling the time of chemical corrosion. Finally, the performance of the μ DMFC with different gradient wettability CCC was tested at room temperature using electrochemical impedance spectroscopy (EIS) and discharge voltage. The experimental results show that the gradient wettability CCC can improve the performance of the μ DMFC by slowing down the rate of cathode flooding. The optimum corrosion time is 5 min at a concentration of 1 mol/L. Under these conditions, the CCC has the best gradient wettability, and the μ DMFC has the lowest total impedance. The discharge voltage of the μ DMFC with corroded CCC is increased by 33.33% compared to the uncorroded CCC μ DMFC. The gradient wettability CCC designed in this study is economical, convenient, and practical for water management of the μ DMFC.