Improving Operational Robustness of NSTF Electrodes in PEM Fuel Cells

Ionomer-free ultrathin electrodes, such as the 3M Nanostructured Thin Film (NSTF) electrode, provide plausible pathways to reduce Pt cost in low temperature fuel cells. However, several operational shortcomings involving relatively poor electrode proton conduction under relatively dry conditions and a tendency to collect water in the cathode at low temperature were observed in our fuel cells. In this study, three approaches of material modifications to the NSTF cathode were developed to enhance the operational robustness of these electrodes. The overall strategies were to improve electrode proton conductivity, water removal capability via the cathode, and water storage capacity. In the first approach, an ionomer was coated onto the NSTF surface to improve electrode proton conductivity and water removal capability, the latter by introducing the hydrophobic domains of the PTFE-like ionomer backbone. In the second approach, silica nanoparticles were coated onto the NSTF surface to improve electrode proton conductivity via retention of thin water films under dry conditions. In the last approach, an additional layer of carbon or Pt/C was placed adjacent to the NSTF layer to improve electrode water removal capability and water storage capacity. It was demonstrated that these approaches can decrease the operational shortcomings of the NSTF electrode and enhance its competitiveness from an overall fuel cell system standpoint. These approaches can relax the system operation constraints needed for NSTF cathodes and can thereby expand avenues for NSTF electrode development. (C) 2012 The Electrochemical Society. [DOI: 10.1149/2.045208jes]