Abstract
The interaction of the metal-support and particle shape has a key role on the determination of the particle size by gas chemisorption. This paper demonstrates mathematically that, assuming metal particles with hemispherical shapes (a common assumption in this type of characterisation) can provide misleading results of up to one order of magnitude. Thus, the metal particle sizes are underestimated when the metal strongly interacts with the support and overestimated when there is a weak metal-support interaction. Additionally, we also demonstrate that although the assumption of spherical shapes always underestimates the size of particles, this error is considerably lower with regular geometries than that associated to the effect of the metal-support interaction due to their effect on the particle shape. Herein, it is demonstrated the importance of introducing the particle-support interaction factor in the chemisorption particle size determination.Graphical
Highlights
The discovery, characterisation and understanding of the unique properties of materials with dimensions between 10-9 and 10-10 m is currently one of the most active research areas due to their potential application in a wide range of fields from catalysis, sensors, biological labelling, photonics, plasmonics, data storage (Pankhurst et al 2003; Panyam and Labhasetwar 2003), etc
This paper further demonstrates that the interaction of the metal and its support can have a more important effect on the resulting average particle size determination due to the conventional assumption of the semi-spherical shape of the particle than the stoichiometric factor
The amount of CO adsorbed in each pulse is quantified by analysing the outlet gas concentration using a thermal conductivity detector (TCD) or a similar detector
Summary
The discovery, characterisation and understanding of the unique properties of materials with dimensions between 10-9 and 10-10 m (nano- and sub-nano scale) is currently one of the most active research areas due to their potential application in a wide range of fields from catalysis, sensors, biological labelling, photonics, plasmonics, data storage (Pankhurst et al 2003; Panyam and Labhasetwar 2003), etc. High-resolution transmission electron microscopy (TEM) provides qualitative and semi-quantitative information about the size distribution and shape of the metal particles as well as their dispersion across the support. Normally using H2 and CO as probe molecules, is widely used either in combination with TEM to provide quantification of the particle size distribution or by itself to calculate the metallic surface area accessible to the probe molecule. It is widely accepted that one of the main limitations of gas chemisorption as a particle size determination technique is the accurate determination of the mentioned stoichiometry factor which strongly depends on the arrangement of the surface atoms. New calculations are proposed to consider the morphology of the metal particle and the contact angle with the support for accurate size determination using accessible chemisorption characterisation
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
