Water Management for μDMFC with Foamed Stainless Steel Cathode Current Collector

Abstract

For micro direct methanol fuel cell (μDMFC), 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 μDMFC’s performance. To this end, a CCC with foamed stainless steel was prepared to assemble the μDMFC due to its absorbency. Further, based on analyzing the gas–liquid two-phase flow characteristics of the μDMFC 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 μDMFC 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 μDMFC 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 μDMFC has the lowest total impedance. The discharge voltage of the μDMFC with corroded CCC is increased by 33.33% compared to the uncorroded CCC μDMFC. The gradient wettability CCC designed in this study is economical, convenient, and practical for water management of the μDMFC.

Cathode diffusion layer and current collector with slotted foam stainless steel for a micro direct methanol fuel cell

“…22 Foam metals are widely used as DMFC current collectors compared to metal ber felts due to their superior mechanical strength. 10,22 Zhao et al 12,23,24 compared hole-type foam stainless steel and hole-type stainless steel as cathode current collectors for mDMFC. It is found that the hole-type foam stainless steel cathode current collectors have a greater power density than the hole-type stainless steel current collectors.…”

“…6 shows that at the FSS-MEA structure provides higher power and limit current densities than the conventional one at 343 K and 298 K. The μDMFC power and limit current densities at 298 K decayed by almost half compared to 343 K. This is because the catalyst activity is not optimal at room temperature and the product water from the cathode blocks the oxygen transfer channel. 24,29…”

“…6 shows that at the FSS-MEA structure provides higher power and limit current densities than the conventional one at 343 K and 298 K. The mDMFC power and limit current densities at 298 K decayed by almost half compared to 343 K. This is because the catalyst activity is not optimal at room temperature and the product water from the cathode blocks the oxygen transfer channel. 24,29 It can be seen in Table 4 that the increase of maximum power density of FSS-MEA mDMFC than CCP-MEA is 74.06% at 298 K, which is higher than that at 343 K (46.14%). It indicates that The FSS-MEA mDMFC has a better drainage effect than the conventional one at room temperature.…”