Abstract
The CO2-induced capillary blocking in anode flow field is one of the key adverse factors to reduce the performance of a micro-direct methanol fuel cell (μDMFC). In order to solve this problem, new polycarbonate (PC) flow field plates with nested arrangement of hydrophilic fuel channels and superhydrophobic gas channels were designed, fabricated, and tested in this work. The gas channels were treated with solvent-induced crystallization using acetone solution. The superhydrophobicity with 160° water contact angle and 2° tilting angle was obtained on the PC substrates. A dummy cell using hydrogen peroxide decomposition reaction and a test loop were separately set up to evaluate the flow fields’ performance. It was found that a 37 % pressure drop decrease can be obtained in the new serpentine flow field compared with that of the conventional one. The benefit of the new flow field to remove gas bubbles was also confirmed by an in situ visualization study on the dummy cell. Results show that the auxiliary superhydrophobic gas channels can speed up the discharge of the gas bubbles from the flow field, which will in turn improve the μDMFC performance.
Highlights
Direct methanol fuel cell (DMFC) has been considered as a promising power source candidate due to its advantages such as high energy efficiency, environmental friendliness, room-temperature operation, facile construction, instantaneous refueling, and low or zero noise
Results show that the auxiliary superhydrophobic gas channels can speed up the discharge of the gas bubbles from the flow field, which will in turn improve the lDMFC performance
In order to enhance the lDMFC performance, the gaseous byproduct produced in the electrochemical reaction needs to be removed effectively
Summary
Direct methanol fuel cell (DMFC) has been considered as a promising power source candidate due to its advantages such as high energy efficiency, environmental friendliness, room-temperature operation, facile construction, instantaneous refueling, and low or zero noise. The similar gas management studies on DMFCs by mixing aqueous solution of sodium bicarbonate (NaHCO3) and weak sulfuric acid (H2SO4) in the DMFC anode flow field were reported by Meng et al [15] and Chuang et al [16]. Hutzenlaub et al studied the effects of wettability on both channel walls and diffusion layers in lDMFC anode They concluded that the hydrophilic flow channel can lead to a minimum pressure drop along the channel, and the bubbles will show virtually no pinning inside the channel [19]. These methods have proven effective for reducing the bubble clogging in DMFC flow fields, the two-phase hybrid delivery in a same channel will still inevitably lead to mutual restraint and interference of different components. The flow fields with and without superhydrophobic gas channels were comparatively studied to determine their different capabilities for mitigating gas slugs blocking
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