Alloy composition kinetic model

Here, Wg and Wq2 represent temperature and composition independent constants called Margules parameters. The substitution of Eq. (11) into Eq. (7) yields the equilibrium potential of the less noble component in the alloy. If this expression is subtracted from the equilibrium potential of the elemental phase defined by Eq. (1), the relation between the underpotentially co-deposited alloy composition and corresponding value of underpotential can be obtained. The example of this approach is shown in Fig. 6 where the composition of UPCD CoPt and FePt is measured as a function of deposition underpotential. The solid lines in the plot indicate the fit of the asymmetric regular solution model. It is important to note that Eq. (11) combined with Eqs. (7) and (1) suggest that composition of UPCD AB alloys (CoPt and FePt) is not dependent on A and B (Co and Fe) deposition kinetics (concentrations in the solutions). 

It is an experimental fact that nitrogen present in austenite solid solution in addition to carbon during the precipitation of vanadium results in the formation of vanadium carbonitrides. The ratio of C/N in the precipitates depends on the alloy composition and the thermal cycle. A comprehensive model of vanadium precipitation kinetics must take this feet into account, and therefore solve the following points ... 

Menon and Landau" point out a number of complications associated with modeling alloy deposition. First, the values for the kinetics parameters of the alloy species are likely to be different from those measured for the pure components. Furthermore, these parameters may vary with the composition of the alloy. Determination of such parameters can be done experimentally from measured alloy composition in well-controlled deposition experiments. A second issue has to do with the difficulty in determining the activities of the alloy components in the solid phase. The activity, which affects the electrode kinetics equation (82), is unity for single-component deposition however, in multicomponent alloy deposition it varies with the nature of the deposited alloy." ... 

In a staged multi-scale approach, the energetics and reaction rates obtained from these calculations can be used to develop coarse-grained models for simulating kinetics and thermodynamics of complex multi-step reactions on electrodes (for example see [25, 26, 27, 28, 29, 30]). Varying levels of complexity can be simulated on electrodes to introduce defects on electrode surfaces, composition of alloy electrodes, distribution of alloy electrode surfaces, particulate electrodes, etc. Monte Carlo methods can also be coupled with continuum transport/reaction models to correctly describe surfaces effects and provide accurate boundary conditions (for e.g. see Ref. [31]). In what follows, we briefly describe density functional theory calculations and kinetic Monte Carlo simulations to understand CO electro oxidation on Pt-based electrodes. 

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