Graphene-Oxide-Modified Metal-Free Cathodes for Glycerol/Bleach Microfluidic Fuel Cells
Cauê A. Martins, Pei Pei, Marisa Tellis, Omar Ibrahim, Erik Kjeang
Abstract
Glycerol is an abundant, inexpensive fuel for miniaturized fuel cells with practical power output. Glycerol electrooxidation is coupled to a cathodic reaction, usually oxygen reduction on noble-metal-based catalysts. However, the slow kinetics of oxygen reduction on nonprecious metal catalysts has limited its applications. Here, we propose the use of hypochlorous acid (HClO from bleach) as a potential liquid oxidant and graphene oxide (GO)-modified carbon paper as a metal-free cathode. GO with high oxidation levels is synthesized and used for in situ flowing deposition on a carbon paper cathode. This unique GO deposition method leads to a homogeneous “blanket” coverage of the wetted fibers exposed to the flow, increasing the active surface area by 3.8 times. The prototype mixed-media microfluidic fuel cell with electrodes in a flow-through configuration featuring glycerol electrooxidation coupled to HClO reduction on GO-modified carbon paper shows 1.72 V open-circuit voltage, 354 mA cm–2 maximum current density, and 110 mW cm–2 peak power density. This unprecedented performance proves that a well-designed in situ electrode modification can be applied to reach high power density without the use of noble metals.