Surface reactions buffer-step models

Oscillatory surface reaction models were first proposed in the second half of the 1970s and developed in two parallel strains. The buffer-step models originated with the work of Eigenberger (274) and models with coverage-dependent activation energies were first proposed by Belyaev et al. (154). 

Additionally, some of the oxidation/reduction models developed so far can be considered buffer-step models. The most extensive theoretical treatment of such a model was performed by Aluko and Chang (273,280,281), who investigated under nonisothermal conditions the model first proposed by Sales et al. (272). The original isothermal model proposed nominally for the CO/O2 system is able to predict oscillations and can be considered a surface reaction model. The model, described in the general terms of Chang and Aluko, consists of... 

There are some oscillatory surface reaction models that contain neither buffer steps nor coverage-dependent activation energies. The first model able to predict oscillatory behavior without these mechanisms was introduced by Takoudis et al. (275,279) and later was analyzed in great detail by McKarnin et al. (286). The model consists of the following three steps, the third of which is strongly autocatalytic ... 

Although this model is able to predict oscillatory behavior, it has one major flaw, because a crucial step in the model is the adsorption of N2 on Pt to yield adsorbed N atoms on the Pt surface. This reaction step is not supported by an existent experimental evidence. This crucial step can also be interpreted as a buffer step as discussed in the general schemes in Section IV,A, and thus omission of this step would probably destroy the oscillatory behavior of the model predictions. 

Numerical Modeling of Transient Isotope Responses On the first step, the authors analyzed in detail five possible heterogeneous methanation models based on two gas phase (CO, CH4) and three surface components (COads, Ca,ads, and Cp,ads) that follow from qualitative analysis of CO labeling data [19,21]. These models contained either a buffer step or parallel routes of methane formation. The homogeneous model having one type of methane intermediate was also considered. A methanation reaction was modeled separately from the entire set of reactions included in the Fischer-Tropsch ... 

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