recent trends in catalysis focused on the nano-structured material, however it is already known that the activity of many reactions depends on the crystallographic orientations.
In fact, both are important. Roughly speaking, the reaction rate will be proportional to the sum of the area of each type of surface plane multiplied by the corresponding rate constant (k1S1+k2S2+...).
If the particle size is decreased, all terms will increase correspondingly. If the particle morphology is properly changed, the terms with high k's will increase and terms with low k's will decrease resulting in the increase of the overall sum.
The best catalyst will have both low particle size and optimal particle shape. But lower size is usually much easier to achieve than correct shape, so amount of the corresponding publications is larger.
In addition to Alexander's answer, as we know that the smaller the particle size the larger the surface area....it means the bigger the possibility of reactants to interact with active sites ( related to the orientation) on the surface area. So nano - size refers to open widely the active sites...and crystallographic orientation refers to ordered or disordered or even defect which is forming the active sites.
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