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Tolerant Chalcogenide Cathodes of Membraneless Micro Fuel Cells

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Abstract

The most critical issues to overcome in micro direct methanol fuel cells (μDMFCs) are the lack of tolerance of the platinum cathode and fuel crossover through the polymer membrane. Thus, two novel tolerant cathodes of a membraneless microlaminar-flow fuel cell (μLFFC), PtxSy and CoSe2, were developed. The multichannel structure of the system was microfabricated in SU-8 polymer. A commercial platinum cathode served for comparison. When using 5 M CH3OH as the fuel, maximum power densities of 6.5, 4, and 0.23 mW cm−2 were achieved for the μLFFC with Pt, PtxSy, and CoSe2 cathodes, respectively. The PtxSy cathode outperformed Pt in the same fuel cell when using CH3OH at concentrations above 10 M. In a situation where fuel crossover is 100 %, that is, mixing the fuel with the reactant, the maximum power density of the micro fuel cell with Pt decreased by 80 %. However, for PtxSy this decrease corresponded to 35 % and for CoSe2 there was no change in performance. This result is the consequence of the high tolerance of the chalcogenide-based cathodes. When using 10 M HCOOH and a palladium-based anode, the μLFFC with a CoSe2 cathode achieved a maxiumum power density of 1.04 mW cm−2. This micro fuel cell does not contain either Nafion membrane or platinum. We report, for the first time, the evaluation of PtxSy- and CoSe2-based cathodes in membraneless micro fuel cells. The results suggest the development of a novel system that is not size restricted and its operation is mainly based on the selectivity of its electrodes.

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