A direct methanol fuel cell with outstanding performance via capillary distillation

Abstract

Facing the severe challenge of methanol crossover, direct methanol fuel cell (DMFC) can hardly operate under high-concentration fuel supply without additional structures, which inevitably restrains its energy density and increases integration difficulty. To address this problem, capillary distillation has been applied for the first time in this work to regulate methanol–water evaporation where a reduced relative volatility of methanol/water and a decreased methanol flux have been realized. A theoretical model has been established to illustrate the impact of porous media properties on the evaporation procedure, followed by a specifically designed experiment which intuitively proves the reduced methanol/water relative volatility via the chosen carbon aerogel. The proposed approach significantly alleviates methanol crossover and water starvation by providing a suitable methanol/water ratio in the vapor supply for DMFCs and thus it could directly operate under high-concentration methanol with a minimal structure, showing an outstanding performance (22 mW cm−2 at 16 mol/L) and stability (a stable output of 20 mW cm−2 for 6 h). The proposed approach not only opens a brand-new window for the design of an all-solid-state /flexible DMFC of high specific energy density, but also expands the potential of DMFC integration, tremendously promoting its development and application in microsystems.