Mixed-Reactant Fuel Cells

About

Fuel cells pose an environmentally cleaner alternative to conventional internal combustion engines. However, current fuel cell technology is not commercially viable due to prohibitive costs of platinum electrocatalysts and stack materials. There exists a present market need for fuel cell technologies that are inexpensive, highly reactive, and highly efficient. Modern research suggests that implementation of anion-exchange membrane electrode assemblies (MEAs) with non-PGM cathode and anodes, where principle operation is based on mixed-reactant fuel cells and non-carbon based fuels, is a viable and attractive alternative to platinum-based fuel cells. To achieve a viable mixed reactant fuel cell (MRFC) the system must follow three kinetic effects: 1) avoid spontaneous thermochemical reaction between the fuel and oxidant that may occur in the bulk single stream mixture or on the catalyst surfaces, 2) provide intrinsic kinetic selectivity of the anode and/or cathode electrocatalysts to suppress mixed-potentials of electrodes, and 3) promote selectivity of the electrodes for mass transfer of the fuel and oxidant to the anode and cathode, respectively. Preciously described MRFCs have failed to optimize these requirements; resulting in lower cell voltages, increased fuel consumption, and decreased energy efficiency. To overcome these challenges borohydrides have been intensely researched as alternative electrochemical fuels. The present invention seeks to utilize direct borohydride-oxygen fuel cells (DBFCs) to address the design and optimization challenges described, enabling the potential for a cost-effective, zero carbon emitting, and commercially viable energy alternative. Researchers from the University of New Mexico and the University of British Columbia have developed an innovative architecture for mixed-reactant fuel cells (MRFCs), eliminating the use of ion-exchange membranes and conventional bipolar flow-field plates. The architecture enables a flexible sandwich of electrodes and separators rolled around an electronically conductive central axis, providing a compact 3D electrode space for the reactions to occur. The cathode and anode layers are each selective to the intrinsic electrode kinetics of fuel oxidation and oxidant reduction, respectively. This design enables simplified fuel and oxygen delivery, while operating at near atmospheric pressure. The highest open circuit voltages and peak power densities reported for any mixed-reactant low temperature fuel cell and conventional dual chamber DBFCs were produced utilizing this Swiss-roll architecture.