Electrospray deposition of catalyst layers with ultra-low Pt loadings for PEM fuel cells cathodes

Suspensions of Pt/C catalyst nanoparticles in Nafion^®-alcohol solutions have been electrosprayed over carbon paper to prepare cathodes for proton exchange membrane fuel cells (PEMFC). Catalyst layers with platinum loading ranging from 0.1 mg_Pt cm⁻² down to 0.0125 mg_Pt cm⁻² and different Nafion^® contents were obtained by this method. Morphological studies of the catalyst layers by SEM inspection showed fractal structures with a high dispersion of catalyst. Fuel cell performance of membrane-electrode assemblies (MEAs) made from these cathodes revealed a strong dependence on the Nafion^® concentration in the electrosprayed suspension. In the platinum loading range 0.1-0.025 mg_Pt cm⁻² and optimal Nafion^® content, a linear relation between fuel cell power density and platinum loading has been found, such that a reduction of platinum content by a factor 4 only reduces the performance by roughly a factor 2. However for the lowest platinum loading investigated, 0.0125 mg_Pt cm⁻², a sharp drop in performance was noticed.