Methanol-tolerant cathode electrode structure composed of heterogeneous composites to overcome methanol crossover effects for direct methanol fuel cell

摘要

A methanol-tolerant cathode electrode composed of heterogeneous composites was developed to overcome CO poisoning and large O_2 mass transfer overpotential generated by methanol crossover as well as the limitation of a single alloy catalyst with methanol-tolerance in direct methanol fuel cells (DMFCs). Two additives, PtRu black and PTFE particles, were well distributed in the Pt/C matrix of the cathode electrode, and had significant effects upon open circuit voltage (OCV) and performance. A small amount of PtRu black protected the Pt surface during the oxygen reduction reaction (ORR) by decreasing CO poisoning. In addition, hydrophobic PTFE particles reduced the O_2 mass transfer overpotential induced by water and permeated methanol in the cathode. Despite only 0.5 mg cm~(-2) of metal catalysts in the cathode, the membrane electrode assembly (MEA) with 3 M methanol showed high performance (0.117 W cm~(- 2)), which was larger than that of the traditional MEA (0.067 W cm~(- 2)).