Fabrication and Optimization of Membrane Electrode Assembly with Support-Less Platinum Catalysts for Space Applications

Abstract

Hydrogen-oxygen fuel cell technology is a critical component for crewed space exploration mission beyond low earth orbit. While lowering platinum loading is of paramount importance for automotive fuel cells, it is not a significant constraint for MEAs used for space applications. As such, support-less platinum black catalysts is a viable choice. Historically, surfactant-stabilized polytetrafluoroethylene (PTFE) emulsion is used as the binder for platinum black electrode. High temperature treatment steps needed for the PTFE emulsion prevents the direct deposition of the electrocatalysts onto the Nafion® membrane. In this study, two alternative materials have been used to replace PTFE emulsion. These include surfactant-free PTFE fine particles and functionalized carbon nanotube with Nafion®. An ultrasonic spray deposition technique was applied to directly deposit support-less Pt black catalyst ink onto the Nafion® membrane. The fabrication process was optimized to produce high performance membrane electrode assemblies that approaching NASA performance target.