Electrospun Nanofiber Anodes of Low Platinum Loading for Hydrogen/Air PEM Fuel Cells

Abstract

Membrane-electrode-assemblies (MEAs) were fabricated with electrospun nanofiber electrodes containing 40% Pt/C, a binder of Nafion and poly(acrylic acid), and a Nafion 212 cation-exchange membrane. MEA performance in a hydrogen/air fuel cell was evaluated at 80°C for a range of anode Pt loadings (0.026-0.126 mgPt/cm2). In all experiments, a nanofiber cathode was used with a Pt loading of 0.10 mgPt/cm2. The electrospun anodes were evaluated to: (i) determine the effect of anode Pt loading on fuel cell performance and (ii) assess the differences in power output when the MEA utilized a conventional slurry catalyst gas diffusion anode. The maximum power density for an MEA with a gas diffusion anode was 432 mW/cm2 at 0.10 mgPt/cm2 Pt loading, whereas the maximum power density for an electrospun anode at the same Pt loading was 491 mW/cm2 (a 14% improvement) It was also found that the measured maximum power density was essentially constant for nanofiber anode Pt loadings in the range of 0.046-0.126 mgPt/cm2. Only at an anode Pt loading of 0.026 mgPt/cm2 did the observed maximum power density decrease. An electrospun anode MEA at a Pt loading of 0.046 mgPt/cm2 produced more power than an MEA with a 0.1 mgPt/cm2 Pt-loaded gas diffusion anode (488 vs. 432 mW/cm2 at maximum power). This study clearly showed that the Pt loading of a hydrogen/air fuel cell anode can be significantly reduced by using an electrospun nanofiber mat.