Performance enhancements of microfluidic fuel cells with flow-through porous electrodes

This thesis presents performance improvements of microfluidic fuel cells with flow-through porous electrodes. The baseline cell is a laminar flow-based, membraneless, microfluidic fuel cell employing vanadium redox species (as electrolytes). The main objective of the current work is to establish a design guideline for microfluidic fuel cells and to propose new design strategies that lead to better performing cells. The fundamental physics including fluid flow, electrochemical reactions in porous media, and convective/diffusive mass transport is closely investigated. Various loss elements during the baseline cell operation such as activation, ohmic, and mass transport losses are identified and compared. Some feasible and practical remedies to reduce the overall losses are proposed and successfully demonstrated: thin film current collector for the overall ohmic loss; nanofoam material as electrodes to reduce the activation loss; and novel concept to overcome mass transport limited performances. Further improvements would be anticipated if both ohmic and fluidic resistances of the nanofoam material are reduced. Uniform distribution of the pore sizes is also important to maximize the utilization of active electrode areas. When combined, the demonstrated technologies and design improvements are anticipated to bring this unique membraneless and catalyst-free fuel cell closer to commercialization as a low-cost power source.