Quantitative Analysis of the Reduction Kinetics of a Pt(Ⅱ) Precursor in the Context of Pt Nanocrystal Synthesis

摘要

In this letter,we report a quantitative analysis of how a Pt(Ⅱ) precursor is reduced to atoms at different temperatures for the formation of Pt nanocrystals with different morphologies and sizes.Our results suggest that in the early stage of a synthesis,the Pt(Ⅱ) precursor is reduced to atoms exclusively in the solution phase,followed by homogeneous nucleation to generate nuclei and then seeds.At a relatively low reaction temperature such as 22 ℃,the growth of the seeds is dominated by autocatalytic surface reduction that involves the adsorption and then reduction of the Pt(Ⅱ) precursor on the surface of the just-formed seeds.This particular growth pathway results in relatively large assemblies of Pt uanocrystals.When the reaction temperature is increased to 100 ℃,the dominant reduction pathway will be switched from surface to solution phase,producing much smaller assemblies of Pt nanocrystals.Our results also demonstrate that a similar trend applies to the seed-mediated growth of Pt nanocrystals in the presence of Pd nanocubes.