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    Effects of power control techniques on hydrogen and oxygen evolution in direct borohydride peroxide fuel cells
    (Pergamon-Elsevier Science Ltd, 2017) Yilmaz, Eyup Semsi; Canan, Belkis; Gunlu, Goksel; Sanli, Ayse Elif
    Direct borohydride/peroxide fuel cells (DBPFCs) have some attractive features, such as high energy density, high theoretical cell power and low operational temperature. The drawbacks that cause performance loss include low efficiency and security challenges. Hydrogen and oxygen evolutions are major issues that should be considered when stacking a DBPFC. These gas evolutions significantly affect the DBPFC performance, efficiency and security. However, the gases were also produced in the case of an open circuit potential and depend on the applied voltage and current. Therefore, in the present study, the effects of cell loading on gas evolution were investigated. The DBPFC was operated under a constant voltage of 1.2 V and controlled using the maximum peak power tracking (MPPT) method. The MPPT control provided higher power generation and higher hydrogen evolution than observed using the constant voltage mode. (C) 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.
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    Performance improvement in direct borohydride/peroxide fuel cells
    (Pergamon-Elsevier Science Ltd, 2017) Sanli, Ayse Elif; Gordesel, Merve; Yilmaz, Eyup Semsi; Ozden, Suleyman Kursat; Gunlu, Goksel; Uysal, Bekir Zuhtu
    Direct borohydride/peroxide fuel cells (DBPFCs) show progressively deteriorating performance during operation for various reasons such as decreasing reactant concentrations, gas evolution and uneven distribution of liquids. The present study aims to emphasize the importance of certain design parameters, such as bipolar plate materials, flow fields and manifold design, in determining the DBPFC performance. Bipolar materials and flow channel design have been investigated. A power density of 67 mW cm(-2) has been obtained with composite graphite and parallel flow channel bipolar plates. It has increased to 87 mW cm(-2) using sintered graphite and then to 93.3 mW cm(-2) using sintered graphite with serpentine flow fields. The stacking of DBPFCs results in a loss of performance and unstable output. The performance has remained nearly unchanged as the cell number was increased by applying an independent cell liquid distribution network (ICLDN). Using an ICLDN, power densities of 98.3, 83.3 and 82 mW cm(-2) have been obtained for single-cell, 3-cell and 6-cell stacks, respectively. Finally, a controlled oxidant feeding system (COFS) has been developed to provide stable output power, and it has demonstrated a stable output power of 6 W for 2.5 h. (C) 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.