Non-linear behaviour of nitric oxide reduction reactions over metal surfaces

Abstract

Chemical reactions carried out under strongly non-equilibrium conditions can result in a variety of interesting effects such as oscillations, chemical waves, kinetic phase transitions, bistability, instabilities and chaos - all of these effects being mathematically due to the strong non-linearities in the kinetic rate equations describing these chemical processes. The present article reviews the various types of non-linear behaviour observed in several NO reduction reactions over Pt-group metals. A large part of this review deals with oscillations and spatiotemporal pattern formation in the reaction over Rh surfaces: the reaction dynamics of this system has been realized on the microscopic, mesoscopic and macroscopic scales using field emission microscopy, photoemission electron microscopy and macroscopic rate measurements respectively. The various mechanisms of this and the other reactions reviewed in this article are also considered.

Parametrization of modified embedded-atom-method potentials for Rh, Pd, Ir, and Pt based on density functional theory calculations, with applications to surface properties

“…In the case of Pt, the value for ␤ (2) even tends to unphysical values ͑i.e., negative values͒, and it is therefore fixed to unity, considering that this hardly affects the energy. This implies that most of the elastic properties are contained in ␤ (0) and that ␤ (2) is the least important parameter in our fits. It should be noted that the weighting parameters influence the energy most, whereas the exponential decay parameters rather determine relaxation effects.…”

“…Due to symmetry, the effective coordination number n of this system depends only on kϭ0,2. Using the previously determined value for w (2) , the parameters ␤ (0) and ␤ (2) can then be determined by fitting the analytical MEAM expression for the energy of this system to the DFT calculations. It turns out, as already indicated by Baskes, that the kϭ2 contribution to the energy of a system close the bulk fcc is rather unimportant.…”

“…arbitrariness due to lack of data. For instance, ␤ (k) ,kϭ0,2, and w (2) were all determined from the shear elastic constants, considered as two constants instead of a function as in the present derivation. Moreover, as already indicated, w (2) is not very sensitive to these shear elastic constants and consequently one cannot obtain a unique value in this way.…”

“…For instance, ␤ (k) ,kϭ0,2, and w (2) were all determined from the shear elastic constants, considered as two constants instead of a function as in the present derivation. Moreover, as already indicated, w (2) is not very sensitive to these shear elastic constants and consequently one cannot obtain a unique value in this way. Although rather unimportant for several bulk properties, w (2) appears to be rather important for surface properties ͑see Sec.…”

“…Examples include the oscillatory behavior of, e.g., NO reactions on surfaces [1][2][3] and the CO-induced lifting of the quasihexagonal, clean surface reconstruction of Pt͑100͒ during catalytic oxidation. 4 Much research on these metals has been performed both experimentally and theoretically.…”