Degradation mitigation in PEMfuelcells using metal nanoparticle additives

Abstract

The efficacy of added freestanding and silica-supported metal (Pt, Pd, Ag, and Au) nanoparticles in mitigating polymer electrolyte membrane (PEM) degradation in an operating fuel cell was investigated. The metal nanoparticles to be added were chosen based on their ability to scavenge free radicals, as confirmed through ex situ measurements using a model free radical 1,1-diphenyl-2-picrylhydrazyl as a test species. Composite membranes were prepared by adding 3 wt% of the freestanding or supported metal nanoparticles to Nafion^®. Membrane electrode assemblies prepared using these membranes were subjected to accelerated degradation tests to determine the fluoride emission rate (FER), a key measure of the macroscopic rate of PEM degradation in an operating fuel cell. The results were as follows: the addition of Ag, Pt, Pd and Au freestanding nanoparticles lowered FER by 35%, 60%, 80% and 90%, respectively, when compared with the recast Nafion^® membrane (control). In the case of silica-supported nanoparticles, more modest reductions were achieved: 40% and 60% in the case of Au on SiO₂ and Pd on SiO₂, respectively. Ag or Pt on SiO₂ resulted in similar FER values as the control. These results suggest that the addition of selected metal nanoparticles with radical scavenging abilities is a promising approach to mitigate PEM degradation in an operating fuel cell.