Chemical diffusion of CO in mixed CO+O adlayers and reaction-front propagation in CO oxidation on Pd(100)

Abstract

Within the framework of a realistic atomistic lattice-gas model, we present the theoretical formulation and simulation procedures for precise analysis of the chemical diffusion flux of highly mobile CO within a nonuniform interacting mixed CO+O adlayer on a Pd(100) surface. The approach applies in both regimes of relatively immobile unequilibrated and fairly mobile near-equilibrated O adlayer distributions. Spatiotemporal behavior in surface reactions is controlled by chemical diffusion in mixed adlayers. Thus, we naturally integrate the above analysis with a previously developed multiscale modeling strategy to describe mesoscale reaction front propagation in CO oxidation on Pd(100). This treatment avoids using a simplified prescription of chemical diffusion and reaction kinetics as in traditional mean-field reaction-diffusion equation approaches. KeywordsAtomistic lattice-gas model, chemical diffusion flux, reaction-diffusion equation, reaction-front propagation, computer simulation, diffusion in gases, oxidation, palladum, reaction kinetics, surface reactions, carbon monoxide Within the framework of a realistic atomistic lattice-gas model, we present the theoretical formulation and simulation procedures for precise analysis of the chemical diffusion flux of highly mobile CO within a nonuniform interacting mixed CO+O adlayer on a Pd͑100͒ surface. The approach applies in both regimes of relatively immobile unequilibrated and fairly mobile near-equilibrated O adlayer distributions. Spatiotemporal behavior in surface reactions is controlled by chemical diffusion in mixed adlayers. Thus, we naturally integrate the above analysis with a previously developed multiscale modeling strategy to describe mesoscale reaction front propagation in CO oxidation on Pd͑100͒. This treatment avoids using a simplified prescription of chemical diffusion and reaction kinetics as in traditional mean-field reaction-diffusion equation approaches.

Swallowtail model for predicting the global bifurcation behavior of CO oxidation reactions

“…Mousa et al [8] investigated the catalytic CO oxidation on PdCu(110) single crystal alloy surfaces, and detected the regions of bistability by mass spectrometric reaction rate measurements. Liu and Evans [9] provided results for the steady-state bifurcation behavior for the catalytic oxidation of CO on single-crystal Pd(100) surfaces under ultrahigh vacuum (UHV) conditions. Pavlenko et al [10] showed that the diffusion of adsorbed CO between two Pt facets in catalytic CO oxidation leads to the appearance of complex multistability.…”

Kinetic Monte Carlo Simulation of Statistical Mechanical Models and Coarse-Grained Mesoscale Descriptions of Catalytic Reaction–Diffusion Processes: 1D Nanoporous and 2D Surface Systems

“…In general, we are interested in finite concentrations, in which case one must consider a many-particle version of the above percolative diffusion problem. 72,228…”

“…The diffusion flux is given precisely by J CO = −Λ CO ∇μ CO , where the conductivity, Λ CO = Λ CO (θ CO ,{O}), also depends nontrivially on θ CO and {O}. 7,72,228 Other components of the conductivity tensor are negligible. Often O mobility is sufficiently high that the adlayer is fully locally equilibrated, and then all these quantities are fully…”

Nonequilibrium chemistry in confined environments: A lattice Brusselator model

“…Such an asymmetric combination is not expected to correctly describe the spatiotemporal behavior of crowded systems, since Fickian diffusion does not respect the conservation laws imposed by the medium constraints. Some recent investigations [8,22], including this work, show that transport can be strongly affected by crowding effects as well. It would thus be interesting to analyze how the conclusions drawn in the limit of ideal diffusion are affected by nonideal contributions.…”

“…Notice the presence of cross-diffusive terms in the righthand side of Eqs. (21) and (22). Because of the balance (7), the effective chemical potential for the X species [μ X − μ * ] depends on the concentration of Y , and vice versa for Y .…”