New insight into Pt nucleation mechanism on Si surface during galvanic displacement deposition

Platinum nanostructures are of large interest because of their electrocatalytic properties, enhanced by the high surface/volume ratio, and find applications in numerous fields from fuel cells and electrolyzers, to gas biosensors and nano-biomedicine. In this work we present a simple procedure, based on spontaneous galvanic displacement, to obtain Pt nanoparticles (PtNPs) directly on Si substrate. The nucleation and growth processes involved in the deposition have been studied by Transmission Electron Microscopy and Rutherford Backscattering Spectrometry. The nucleation is quite complex and includes, first, the generation of primary non-growing clusters, with size smaller than 2 nm. Then, for longer deposition times, larger particles are formed, resulting from dynamic coalescence of primary clusters with/or single ion attachment processes. The growth of such larger particles follows the prediction of the classical diffusion limited model. Moreover, the large nanoparticles are poly-crystalline and exhibit a nano-porous structure, in agreement with a mixed aggregative-diffusion limited growth. The nano-porous structure implies a high internal surface area, therefore making these particles particularly promising as efficient catalysts.