Direct growth of carbon nanofibers on carbon-based substrates as integrated gas diffusion and catalyst layer for polymer electrolyte fuel cells

One-dimensional carbon nanostructures are considered promising for application as catalyst support in polymer electrolyte fuel cells, replacing the most widely used carbon black, due to their physico-chemical properties and high surface area. Different morphologies of carbon nanofibers, by varying the graphene layers orientation with respect to the fibre axis, exhibit different amount of available open edges that can act as anchorage site for catalyst nanoparticles. CNF are grown on graphite paper by a controlled plasma enhanced chemical vapour deposition and then used as substrates for Pt electrodeposition. The CNF direct growth on carbon paper allows having single layer electrodes with both diffusive and catalytic layer function. Moreover, the replacement of conventional ink deposition methods with electrodeposition for platinum dispersion, allows greatly reducing the catalyst load, increasing at the same time its utilization and performance. The innovative electrodes are characterized by field emission gun scanning electron microscopy and X-ray photoelectron spectroscopy to assess the morphological properties, and by cyclic voltammetry in H2SO4 and H2SO4 + CH3OH to determine the electrocatalytic activity and long term stability. The comparison with an electrode made of conventionally deposited Pt catalyst by ink method on commercial carbon black shows better performance for the developed Pt/CNF electrodes.