Effects of platinum loading on performance of proton-exchange membrane fuel cells using surface-modified Nafion® membranes

The interface between the electrolyte and electrode catalyst plays an important role in determining the performance of proton-exchange membrane fuel cells (PEMFCs) since the electrochemical reactions take place at the interface in contact with the reactant gases. To enhance catalyst activity by enlarging the interfacial area, the surface of a Nafion® membrane is roughened by Ar+ ion beam bombardment that does not change the chemical structure of the membrane, as confirmed by FT-IR spectra. Among the membranes treated with ion dose densities of 0, 1015, 1016, 5 × 1016 and 1017 ions cm−2 at ion energy of 1 keV, the membrane treated at ion dose density of 5 × 1016 ions cm−2 exhibits the highest performance. Using the untreated and the treated membrane with 5 × 1016 ions cm−2, the effects of platinum loading on cell performance are examined with Pt loadings of 01, 0.2, 0.3, 0.4 and 0.55 mg cm−2. Except for a Pt loading of 0.55 mg cm−2 where mass transport limits the cell performance, the single cell using a treated membrane gives a higher performance than that using an untreated membrane. This implies that the cell performance can be improved and the Pt loading can be reduced by ion beam bombardment.