Computational Catalyst Screening Strategies

FIGURE 7.5 Design of an improved CoMo ammonia synthesis catalyst by use of the interpolation principle. Reprinted with permission from Ref. [65]. American Chemical Society. 

A critical factor in catalyst performance that is not accounted for by the simple activity screening exercises described earlier is catalyst stability. Both heterogeneous catalysts and electrocatalysts are subject to a number of deleterious processes that can degrade the eatalyst over time. Without some accounting for these factors 

FIGURE 7.6 Combinatorial display, arranged in elemental periodic order, of predicted rates for the electrocatalytic HER in acidic solutions. Binary surface alloys with a color code of yellow have the highest predicted activity. Reprinted with permission from Ref. [71]. Nature group. (See insert for color representation of the figure.) 

The aforementioned phenomena, while by no means the only processes that may degrade catalysts, are relatively common and must be taken into account when 

FIGURE 7.7 Theoretically derived volcano for the electrocatalytic Oxygen Reduction Reaction in acidic media. Experimental data points are indicated by solid or filled circles. PtjY is an improved alloy catalyst discovered by computational catalyst screening. Reprinted with permission from Ref. [74]. Nature group. 

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Although many useful strategies have been developed to model heterogeneous catalytic and electrocatalytic reactions, the approach that has been most successful in computational catalyst screening involves the development and use of descriptors, which are simple thermodynamic or kinetic parameters that are directly related to the catalytic properties of the material and that can be rapidly evaluated with electronic structure (primarily. Density Functional Theory— DFT) calculations. In a typical descriptor-based catalyst search, an approximate functional relationship between the... 

The computational study of the osmium dihydroxylation of aliphatic al-kenes is much more complicated than the case of aromatic alkenes due to the large number of conformations that the former could adopt. To overcome this issue, we considered the system to be composed of two different parts the catalyst and the olefin. For the catalyst, the conformation considered is that from the X-ray structure. As already shown in the study of styrene [95], and in some experimental works [98], the catalyst is a fairly rigid molecule. For the aliphatic alkenes under study, there is a large number of possible conformations in addition, the stability of an olefin conformation is also affected by the interactions between the olefin substituent and the catalyst. Therefore, the catalyst must be included in the conformational search. The conformational analysis was done using a scheme based on the systematic search approach [99]. The strategy consisted of two parts first we developed a method to identify all of the possible conformations afterwards, we screened all of the possible conformations at MM level to select the most stable. Finally, we only carried out the relatively expensive QM/MM calculations on these selected conformations. 

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