Electrocatalyst computation studies

In conclusion, the computational study of ternary Pt-Ru-X alloys suggests that future strategies toward more active electrocatalysts for the oxidation of methanol should be based on a modification of the CO adsorption energy of Pt (ligand effect), rather than on the enhancement of the oxophilic properties of alloy components (enhanced bifunctional effect). 

The above results demonstrate that computational screening is promising technique for use in electrocatalyst searches. The screening procedure can be viewed as a general, systematic, DFT-based method of incorporating both activity and stability criteria into the search for new metal alloy electrocatalysts. By suggesting plausible candidates for further experimental study, the method can, ultimately, result in faster and less expensive discovery of new catalysts for electrochemical processes. 

Investigations of enzyme-catalyzed direct electron transfer introduce the basis for a future generation of electrocatalysts based on enzyme mimics. This avenue could offer new methods of synthesis for nonprecious metal electrocatalysts, based on nano-structured (for example, sol—gel-derived) molecular imprints from a biological catalyst (enzyme) with pronounced and, in some cases, unique electrocatalytic properties. Computational approaches to the study of transition state stabilization by biocatalysts has led to the concept of theozymes . " ... 

As discussed above, the oxygen adsorption and reduction processes are often simulated either on small Pt clusters or flat surfaces. However, both experimental measurements [51, 52] and computational calculations [53, 54] indicate that nanosized electrocatalysts show a considerably different catalytic activity from extended flat surfaces. These investigations would suggest that effects observed with particle size reduction go well beyond the increase in surface area and involve fundamental physical and chemical changes in the reaction steps. Han and his coworkers [55] studied explicitly Pt nanoparticles with 1 and 2 nm sizes and compared their chemical adsorption properties to those of an extended flat Pt (111) surface. As atomic oxygen (O) and hydroxyl group (OH) are two species of considerable importance [56], they focused on effect of particle size and Pt coordination on the chemisorption energies of O and OH. 

Analyses of responses aiming to define the characteristics of the electrode deposit and the details of the mechanism operative in anodic oxidations or cathodic reductions are also very challenging and rare in the case of amperometric sensing on modified electrodes, due to the complexity of most systems with respect to the bare ones. On the other hand, the superior performance of new computers may lead to unprecedented sophisticated simulations. In the case of composites based on nanosized materials, studies of the diffusion to micro- and nano-electrode systems may be exploited [234]. Similarly, calculations regarding the reaction mechanisms based on density functional theory have been exploited to give a rationale to the performance of a number of electrocatalysts [235]. 

Among the computational approaches, study of adsorption abilities (reactant, intermediate, and product) is the most widely employed approach in understanding catalyst activity and the design of electrocatalysts. The interaction between catalyst and reaction species governs the reaction, and adsorption energy is relatively easier to compute than reaction energy and activation energy, especially the latter, which is computationally expensive. 

This section presents a review of atomistic simulations and of a recently introduced meso-scale computational method to evaluate key factors affecting the morphology of CLs. Most of the effort in molecular dynamics simulations for PEFCs has concentrated on dynamic motion of proton and water through the hydrated membrane [96-104], Little attempt has been made to employ MD techniques for elucidating the structure and transport of CLs, particularly in three-phase systems of carbon/Pt, ionomer, and gas phase. In the following subsections, we discuss various MD simulations to study the transport and dynamic behavior of CLs in terms of water and proton diffusivity, Pt-supported electrocatalyst, and microstructure formation. 

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