Search

Water management is a critical issue to be solved efficiently for an air-breathing direct methanol fuel cell (DMFC). The cell performance decreases sharply once the water flooding occurs. In this paper, a novel strategy of water removal is proposed by incorporating a functional self-made expanded metal mesh, which can be used as the cathode flow field in a DMFC. Experiments show that water can be directly discharged in the form of water film or water line from the water outlet to the bottom underneath the expanded mesh. The water management can be further improved by using absorbent cottons, suitable feed rates and an upright texture direction of the metal mesh. Results also show that only a few mesh openings are blocked by water when the tested device tilts from 60° to 120°. In a real DMFC, the expanded mesh displays an excellent ability in water removal compared to the traditional perforated flow fields. The cathode water only gathers at the bottom and covers very few mesh openings. This new method helps efficiently avoid the issue of water flooding at the cathode using the expanded mesh.

Surface-pattern engineering, as a key strategy to fabricate high-performance Nafion membranes for fuel cells, plays an important role in surface functionalization of the membrane, optimization of the three-phase boundary, water management, proton transport, etc. Considerable efforts have been dedicated to developing advanced-patterned Nafion membranes with single-scale (nanoscale or microscale) and multiscale-patterned structures which are believed to improve the performance of membrane electrode assemblies (MEAs) for fuel cells. In this review, the recent progress in surface-patterned Nafion membranes (SPNMs) equipped with single-scale-patterned structures (including nanostructured and microstructured Nafion membranes) is firstly highlighted. The structural features and construction methods of SPNMs are discussed in detail. The effects of single-scale SPNMs on the construction and performance of fuel cells are also analyzed. Followed is an overview of the recent advances in fabricating multiscale SPNMs based on different strategies with a specific introduction on the membrane related effects on fuel cells. Finally, the future development direction and certain perspectives on the current issues of SPNMs are presented.

Management of the produced carbon dioxide (CO2) is important to improve the performance of a liquid-feed direct methanol fuel cell (DMFC). This work investigates the CO2 bubble behaviors and the two-phase flow characteristics, using a single sinusoidal corrugated channel as the anode flow field. The magnitude and gradient of the fluid velocity in this channel is higher than the traditional straight pattern, as proven by tracking CO2 bubbles. The use of high magnitude and gradient of velocity enhances CO2 emission and fuel delivery, as well as increases the pressure drop. The vortices in the disturbance structure of the corrugated channel help uniformly deliver the reactants and separate bubbles away from the channel wall. Using excessive values of amplitude A and angular frequency W in the corrugated channel causes serious bubble deformation and extra energy consumption. The effect of disturbance structure is negligible with small values of these two parameters. The cell with a corrugated channel shows a higher performance at different feed rates and concentrations of the methanol fuel. The optimal value of A and W are respectively 0.1and 5. The visualization tests demonstrate that the appearance of CO2 bubbles in the corrugated channel is consistent with the simulation results.