Nanostructured Platinum (H I -ePt) Films:  Effects of Electrodeposition Conditions on Film Properties

A systematic investigation into the effects of deposition conditions on the electrochemical properties and nanostructure of high surface area (up to ∼460 m2 cm-3) mesoporous platinum films (HI-ePt) obtained by electroreduction of hexachloroplatinic acid (HCPA) from an hexagonal lyotropic liquid crystalline phase is reported. The surface area, repeat distance, and regularity of the nanostructure and the surface morphology of the films were shown to depend on the deposition conditions. In particular, the deposition potential was found to have a notable effect on the film surface area and on the uniformity of nanostructure. The results obtained are explained by variations in the efficiency of the deposition process and the relative contributions of competing reactions. Increasing the temperature of electrodeposition was found to increase significantly the surface areas of the films and to increase the repeat distance of the nanostructure. In addition, a roughening of the films on both a micro- and a nanometer scale was observed with an increase in temperature. We also found that the thickness of the electrodeposited films scaled linearly and that the volumetric surface area was constant, with the charge passed during the electrodeposition process, indicating uniform accessibility of the pore system.