In-Situ Characterization of Microfluidic Redox Battery with Dual-Pass Architecture
The cell is fabricated using soft lithography techniques in polydimethylsiloxane (PDMS) using an SU-8 master and then bonded to a glass substrate. Porous carbon paper is cut into rectangular strips and placed as the electrodes for the device. Details about the vanadium redox electrolytes preparation and the device fabrication are described elsewhere .
Each cell portion is tested individually with vanadium redox species delivered at low and high flow rates and the results are used to quantify the species crossover losses, which result in a mixed potential and thus causes a drop in open circuit potential and overall performance. The crossover losses at the downstream portion are reduced from 41 mV at 10 μL/min to 13 mV at 100 μL/min. The upstream cell portion demonstrates maximum power density of 744 mW/cm2 at a high current density around 1000 mA/cm2. This compares favorably to all previously reported conventional counterparts.
Moreover, the two cell portions are connected in parallel to resemble the original cell with dual-pass architecture  which allows assessing the contribution of the inlet and outlet passes of the dual-pass architecture in-situ. The fuel utilization is estimated from the current outputs of the two portions at low and high flow rates, and the contribution of the downstream cell portion is found to be on the same order as that of the upstream portion. Overall, the results of this study are expected to provide a deeper understanding of the reactant conversion and reactant crossover phenomena in co-laminar flow cells which will be useful for future device optimization.
Funding for this research provided by the Natural Sciences and Engineering Research Council of Canada (NSERC), Canada Foundation for Innovation (CFI), and British Columbia Knowledge Development Fund is highly appreciated.
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