Stability of platinum particles on a carbon substrate investigated by atomic force microscopy and scanning electron microscopy

To investigate the stability of platinum particles, a flat carbon substrate coated with platinum nano-particles was made as a model of PEMFC cathode catalyst. Changes of the platinum particles caused by potential retention in acid solution were observed by FE-SEM. Stability of the carbon substrate without platinum was also observed by AFM. The position of the AFM and FE-SEM observation before and after each potential retention was identical so that morphological change could be traced like in situ experiments. Behaviors of each particle, i.e. disappearance, migration and aggregation, was observed after potential retentions. Statistical analysis of the images revealed that small platinum particles on the model electrode decreased in number, especially at high potentials and under an oxygen atmosphere.