ICP Surfaces for Facilitating Metal Nanoparticle Growth

Utilizing ICPs as potential platforms for supporting nanoscale structures has been investigated to provide novel supported catalysts. The concept of embedded metal nano-particles was recently presented by Zhou et al. [98, 99]. In this instance the metal nanoparticles were embedded in the polymer matrix and therefore protected from the chemical environment. Wang and co-workers [172] employed a similar approach by chemical reduction of AuCl3 or Pd(NO3)2 by polyaniline powder in either aqueous dispersions or in NMP, a common solvent for the EB form of PAn. Reduction of palladium nanoparticles was slow with EB; hence the polyaniline was initially reduced to the leucoemeraldine base form in order to facilitate reduction of the Pd2+ to its metallic state. The nanoparticle sizes for the Au and Pd were observed to be 20 nm from NMP solution and 50200 nm from polyaniline powder. Gold-polyaniline nano-composites have been prepared by the chemical reduction of

HAuCl4 and simultaneous polymerization of aniline to produce 26 nm Au nanoparticles dispersed in the polyaniline powder matrix [173].

Platinum and platinum oxide nanoparticles, 4 nm in size, have been successfully deposited onto polypyr-role/polystyrene sulfonate colloidal dispersions (with dimensions ranging from 30 to 1000 nm) [174] for use as catalysts. Pt(NH3)4Cl2 and Na6Pt(SO3)4 metal salts were reduced by formaldehyde or H2O2 respectively in order to form Pt nanoparticles on the ICP colloid surface. These nano-composite dispersions have been reported to be effective catalysts for oxygen reduction in a proton exchange membrane fuel cell, indicating that the metal catalytic particles are accessible for chemical interaction.

Polythiophene has also been investigated as a potential substrate for the formation of catalytic platinum nano-particles, 2-4 nm in size, for oxygen reduction. The Pt nanoparticles were homogeneously deposited across a predeposited polythiophene film by direct electrodeposition from a solution of 12.5 M H2SO4 and 4 mM H2PO4. The resulting composite was produced in a similar fashion as other electrocatalysts such as carbon-supported platinum.

0 0

Post a comment