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UBC Theses and Dissertations

Development of a Swiss-roll mixed-reactant fuel cell Aziznia, Amin

Abstract

Capital and operating costs of fuel cell systems must be reduced before they can be competitive with conventional energy conversion technologies. This dissertation concerns the development of an unconventional fuel cell aimed at meeting that challenge. Presented here, for the first time, is a novel cylindrical Swiss-roll mixed-reactant fuel cell (SR-MRFC) that eliminates expensive and failure-prone components of conventional fuel cells. The proof-of-concept of the SR-MRFC was performed both in monopolar and bipolar architectures. In the monopolar case 3D anodes with platinum or with osmium catalysts were coupled to a gas-diffusion MnO₂ cathode in a 20×10-⁴ m² single-cell SR-MRFC, operated with a two-phase mixture of 1 M NaBH₄/2M NaOH(aq) + O₂(g). Instead of a Nafion® membrane, a porous diaphragm was employed. At 323 K, 105 kPa(abs), the peak superficial power densities of the SR-MRFC with the platinum and osmium anode catalysts were up to respectively 2230 and 1880 W m−² with good performance stability during 3 hr continuous operation. These values are the highest power densities ever reported for MRFCs operating under similar conditions and match the highest reported values for conventional dual chamber PEM direct borohydride fuel cells. Scale up of the single-cell SR-MRFC to 100×10-⁴ m² and 200×10-⁴ m² gave corresponding peak superficial power densities of 900 and 700 W m-², while the 20×10-4 m² bipolar reactors produced peak volumetric power densities of 267 and 205 kW m-³. This work also explored the feasibility of electroreduction of N₂O on Pt and Pd in the cathode of a MRFC to generate electricity from N₂O in the tail gases of industrial processes. Here the SR-MRFC was operated using two-phase fuel + oxidant mixtures of 1 M NaBH₄ / 2M NaOH(aq) + N₂O(g) and 0.5 M CH₃OH/2 M NaOH(aq) + N₂O(g). At 323 K, 105 kPa(abs) the peak superficial power densities for the mixed NaBH₄- and MeOH-N₂O systems were respectively 340 W m-² (Pt anode/Pd cathode) and 38 W m-² (PtRu anode/Pd cathode). This work demonstrates for the first time that co-generation of electricity and abatement of N₂O may potentially compete with thermochemical processes of N₂O capture currently under development.

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Attribution-NonCommercial-NoDerivatives 4.0 International

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