A new water management system for air-breathing direct methanol fuel cell using superhydrophilic capillary network and evaporation wings

Oxygen starvation caused by water flooding in cathode is a key performance bottleneck for air-breathing direct methanol fuel cell (DMFC). To solve this problem, we present a new water management system consists of superhydrophilic capillary network and evaporation wings in this work. The cathode flow field (CFF) with water management system (WMCFF) is obtained by fabricating capillary network on titanium substrates with micro machining techniques. A pair of evaporating wings made of carbon papers are used to collect water from the capillary network and further evaporate them into the air quickly. Results show that, before a long-term discharge test, the initial peak power density (P-max) of WMCFF-DMFC is 38.9% higher than that of the conventional cathode flow field DMFC (CCFF-DMFC). After 2 and 4 h discharge, the performance gaps between the two DMFCs become larger, and the P-max of WMCFF-DMFC increases by 55.6% and 74.3% compared with that of the CCFF-DMFC, respectively. Moreover, the corresponding P-max decline rate in the WMCFF-DMFC is only about 12% and 27% of that in the CCFF-DMFC. This suggests that the new water management system can effectively prevent water flooding in cathode and significantly improve the performance and stability of the air-breathing DMFCs.