Control of nanoparticle aggregation in PEMFCs using surfactants

This research is aimed at investigating the aggregation behaviour of catalyst nanoparticles in proton exchange membrane fuel cells (PEMFCs). Electrocatalyst nanoparticles are prepared using various surfactants which are known to prevent aggregation. Well-dispersed nanoparticles are thought to have a higher available surface area, hence exhibiting higher catalytic activity than aggregated nanoparticles. Platinum nanoparticles have been successfully prepared in aqueous dispersion using tetradecyltrimethylammonium bromide (C14TAB), cetyltrimethylammonium bromide (C16TAB) and nonylphenolethoxylate (NP9). The aggregation behaviour of the particles was studied using transmission electron microscopy, Nanosight (Carr B, Hole P, Malloy A. Sizing of nanoparticles by visualizing and simultaneously tracking the Brownian motion of nanoparticles separately within a suspension. In: Eighth International Congress on Optical Particle Characterisation, Karl-Franzens University Graz, 2007) and dynamic light scattering. Electrochemistry results for the oxygen reduction reaction (ORR) on the platinum disc in the absence and in the presence of surfactants show that the surfactants have a marked effect on the reaction. The movement of the onset potential to lower voltages suggests the surfactant is poisoning the catalytic sites on the electrode. This shows that the surfactant molecule selection is vital to obtaining effective fuel cell catalyst.