Precision Engineering of Co-Laminar Flow Cells for Electrochemical Energy Conversion

Abstract

Most electrochemical cells used for energy conversion utilize a physical separator such as an ionomer membrane to keep reactants separated and prevent a mixed potential from reducing energy efficiency. A new class of electrochemical cell achieves this separation by design of channel dimensions such that reactant flows remain laminar. These co-laminar flow cells (CLFC)1,2, which include both fuel cells and flow batteries, are generally microfluidic and constrained in operation by the diffusion time of reactants across the channel. Due to their small scale and lack of a membrane, these co-laminar flow cells are both simpler and lower cost devices which make them well suited as an experimental platform for understanding electrochemical energy conversion. The cells in this study are based on flow-through porous carbon electrodes with vanadium redox reactants dissolved in sulfuric acid as both fuel and oxidant. This presentation reveals some of the advancements made with these cells over the past year and the lessons learned which may be applied to larger scale conventional flow batteries and fuel cells. Some of the topics to be discussed include electrode enhancement to improve the limiting reaction rate, supported by both ex situ and in situ characterization of the flow-through porous electrodes. Reaction kinetics are studied using a custom-developed three-electrode analytical cell for electrochemical analysis of flow-through porous electrodes. Multiphysics modeling work based on this characterization provides insight into some of the design principles which can be used to maximize the power density of these devices. Acknowledgements Funding for this research provided by the Natural Sciences and Engineering Research Council of Canada (NSERC), Canada Foundation for Innovation, and British Columbia Knowledge Development Fund is highly appreciated.