Moisturized anode and water management in a passive vapor-feed direct methanol fuel cell operated with neat methanol

This paper investigates the moisturized anode and water management of a vapor-feed direct methanol fuel cell operated with neat methanol. Three methods of water management are experimentally compared, including water storage in a fuel reservoir, active water vapor supply and water recovery from the cathode to the anode. A water management layer for water recovery is introduced to the cathode, which is made of a quasi-superhydrophobic sintered porous metal plate (SPMP) to enhance water back diffusion (WBD). Results prove that each of these methods can improve the cell performance. WBD enhancement based on the use of a SPMP is proven to be the most effective way. It is also found that combination of different methods may more promote the cell performance. Using a WBD enhancement layer under the condition of active water vapor supply can completely eliminate performance decline in the early stage of constant-load discharging. For fully-passive operation, a higher catalyst loading at the cathode helps retain stable performance when a WBD enhancement layer is used. Based on this design, the passive vapor-feed DMFC fed with neat methanol can achieve a maximum power density of 21 mW cm−2.