Platinum film growth from copper seeds 50 mL of an aqueous 0.33 mM (34 mg) H 2 PtCl 6 •6H 2 O solution was added to the stirred 150 mL Cu-SiO 2 particle suspension (1000 RPM) under continuous degassing. The galvanic exchange proceeded for 30 minutes, before dropwise addition of 1.35 mL formaldehyde to the suspension to initiate the auto-catalytic growth of the Pt films.