Examples of size effects on catalytic CO oxidation using metal nanoparticles

Examples of size effects on catalytic CO oxidation using metal nanoparticles 

The discussion in the following focuses on just a few selected examples illustrating the effects of particle size with particular attention to the approach authors have taken in fabricating model catalysts. Different trends, such as onsets and maxima in catalytic activity within wide range of sizes, or behavior of catalysts differing by just one atom, are highhghted. 

More detailed research revealed that catalysts prepared by DP had an order of magnitude higher turnover frequency (TOF) compared to Pt-based analogs and four orders of magnitude higher TOF compared to Au-based catalysts prepared via photodeposition or impregnation methods [96]. Importantly, catalysts made by such relatively easy and simple approaches contained particles with relatively wide size distributions [96]. 

Furthermore, as the gold precursors used in such preparations often contain significant amount of Cl, catalyst washing procedures aimed to remove this impurity became rather important because the presence of even trace amounts of Cl can negatively impact a catalyst s activity [100]. 

Overbury et al. [101] elucidated the size effects in a family of rather closely related tailor-made Au-Ti02 (P-25) catalysts (i.e., use of the same support, Au loadings, and impurity levels to minimize effect of non size-related factors), where particle size was varied using variations in heat treatment. It was demonstrated that the TOF of CO oxidation at 298 K changes as a function of particle size. Namely, the TOF for 7.2 wt% catalysts was proportional to while that for 4.5 wt% 

---