The shape and size of the nanoparticle (geometric shape) significantly influence the resonance.

In general, the smaller the nanoparticles, the larger the specific surface area will be. Therefore, as catalysts, they could perform better since more active sites could be exposed. As for the geometry, it you could control the crystallographic planes on the surface, you may tailor the catalytic properties.

Ali Behrad Vakylabad

You ask 'Are there any relationships between the shape and size of a nanoparticle and its activity as a catalyst?'.

The answer is 'Yes, there are'.

• In general terms, the smaller the size of the particle then the greater the specific surface area and therefore the activity is increased
• Different crystal faces have different activities in relation to chemical reactions and altering the shape changes the proportions of faces. This can either enhance activity or depress side reactions such as poisoning (or a combination of both)

Ali Behrad Vakylabad

I recommend 2 books to aid you in your quest for answers. Both books can be obtained relatively inexpensively through Abebooks:

• G C Bond Catalysis by Metals Academic Press (1962)
• J R Anderson Structure of Metallic Catalysts Elsevier Science & Technology Books (1975)

Geoff Bond was my Ph.D supervisor.

Thank you all dear friends: Alan F Rawle, Bin Zhao, Saad Zahraw Sekhi for your kind and very useful responses. There is a point:

These cases are quite theoretically and in many cases true. However, some other interesting results from the literature. for example, Article:

Boudart, M.; Delbouille, A.; Dumesic, J. A.; Khammouma, S.; Topsøe, H. Surface, Catalytic and Magnetic Properties of Small Iron Particles: I. Preparation and Characterization of Samples. J. Catal. 1975, 37 (3), 486–502. https://doi.org/10.1016/0021-9517(75)90184-0.

This paper states that the size of iron nanoparticles from 1.5 to 30 nm has an inverse effect on the catalyst activity so that 30 nm is the most active detected, although iron nanoparticles with 1.5 nm have the highest exposed metal surface.

Ali Behrad Vakylabad

Yes, generalities are invariably dangerous. It may be that, in your example, the smaller particles are active for a non-desired reaction or the stoichiometry may be compromised by the particles being too small to adsorb both reactants side-by-side on the surface or that the smaller particles exhibit different, less-reactive, faces or the smaller particles are not pure but tied to the surface ja niin edellen…

Yes, the variables are dependent, high superficial area are associated with low particle size and these are associated with more active expossed aires of the nanoparticle. So, these structural properties are beneficiar for the Activity of nanoparticles

Dear Ali Behrad Vakylabad first of all let my say that I agree with the expert answers provided by Alan F Rawle. In addition, I would like to suggest to you a very interesting review article which will certainly help answering your interesting technical question:

Size- and shape-dependent catalytic performances of oxidation and reduction reactions on nanocatalysts

https://pubs.rsc.org/en/content/articlelanding/2016/cs/c6cs00094k

The paper has also been posted on this platform, but unfortunately not as public full text:

Article Size- and Shape-Dependent Catalytic Performances of Oxidatio...

However, I noted that three of the five authors are RG members. Thus it should be no problem to request the full text of the review directly from one of them via RG.

Good luck with your research!

Yes dear as the particle size decreases the surface area of adsorption increases and the photocatalytic activity increases

Alan F Rawle

Sir, I really admire the way you share your knowledge and answer questions. Sir, if "generalities are invariably dangerous", how can one reproduce the results?

Aarif Hussain Shah

Thank you for your compliments. 'I try my best to be just like I am, But everybody wants you to be just like them' (Robert Zimmerman).

You ask "if generalities are invariably dangerous", how can one reproduce the results? The answer is with specifics (related to the experiment and conditions, the materials, and knowledge of the techniques used to explore the properties and so on). In general (I'm using this again when generalities are problematic) different techniques provide different answers and understanding these differences is key to understanding how the material behaves (not as a set of numbers but related to critical quality attributes (CQA's) or product performance indicators (PPI's).)

Thanks to all friends for your invaluable answers.

We need to be more cautious about the catalysts. Our screening tests in the laboratory for converting furfural from cellulose and hemicellulose to 2-methyl furan (2-MF) using a range of industrial catalysts showed that activity and selectivity related to the catalysts in practice showed no significant relationship to particle size and even BET. With these examples, especially in the case of the catalysts, we may not be able to quickly conclude that there is a direct link between catalytic active sites and BET. Perhaps these contradictions lead us to conclude that we must define another, perhaps more comprehensive, connection to the activity and selectivity of a catalyst, rather than or along with the specific surface area (BET), Particle size distribution (PSD), pore size, ….

Actually, the relationship among form, composition and activity is very clear. The smaller the particle size, the larger the specific area of the material and therefore the higher the activity. That said, obviously the activity will be a function of the specificity of the catalyst. Crystallinity is also another factor to consider. On the other hand, the phase in which the material is found greatly affects the activity: for example, in TiO2 it is not the same to use anatase, rutile, or P25 (which is a mixture of both phases). The phases affect the adsorption and consequently the activity ...

They are very general lines, but it is what it is ...

Actually, the relationship among form, composition and activity is very clear. The smaller the particle size, the larger the specific area of the material and therefore the higher the activity. That said, obviously the activity will be a function of the specificity of the catalyst. Crystallinity is also another factor to consider. On the other hand, the phase in which the material is found greatly affects the activity: for example, in TiO2 it is not the same to use anatase, rutile, or P25 (which is a mixture of both phases). The phases affect the adsorption and consequently the activity ...

They are very general lines, but it is what it is ...