EXISTENCE OF A "HOT" ATOM MECHANISM FOR THE DISSOCIATION OF O2 ON Pt (111) AND THE PHASE DIAGRAM OF CATALYTIC OXIDATION OF CO

Khan, K M; Iqbal, Kefi

doi:10.1142/s0218625x04005846

Cited by 6 publications

(4 citation statements)

References 19 publications

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“…Inspired by experiments based on scanning tunneling microscopy that point toward a "hot atom" mechanism according to which the two oxygen atoms are propelled apart upon dissociation [15], we show that the nonphysical transition at y 1 can be eliminated by making simple changes to the entrance mechanism of the oxygen atoms in the ZGB model. Similar mechanisms have been suggested by other authors [16][17][18]. In the ZGB model upon adsorption the oxygen atoms are located one lattice unit apart.…”

Section: Introductionsupporting

confidence: 77%

Comparison between different oxygen adsorption mechanisms for the catalytic oxidation of CO on a surface

Ojeda

Buendı́a

2012

JCM

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PACS numbers:We study by kinetic Monte Carlo simulations the dynamic behavior of a Ziff-Gulari-Barshad (ZGB) model for the catalytic oxidation of CO on a surface. It is well known that the ZGB model presents a continuous transition between an oxygen poisoned state and a reactive state that it is not observed in nature. Based on some experimental results that indicate that the oxygen atoms move away from each other upon dissociation at the surface, we modify the standard ZGB model by changing the entrance mechanism of the oxygen molecule. We study three different ways in which the oxygen atoms can be adsorbed at the surface such that the nonphysical continuous phase transition disappears. We calculate the phase diagram for the three cases and study the effects of including a CO desorption mechanism. * Electronic address: buendia@usb.ve

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Section: Introductionsupporting

confidence: 77%

Comparison between different oxygen adsorption mechanisms for the catalytic oxidation of CO on a surface

Ojeda

Buendı́a

2012

JCM

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“…Some modeled the catalyst surface as a hexagonal lattice instead of a square lattice [15,16]. Some studied the effects of oxygen atoms adsorbing at two non-neighboring sites ('hot' dimer adsorption) [17][18][19][20][21] or as a result of nearestneighbor repulsive interactions [22][23][24][25]. Others considered diffusion of the adsorbed species [3,[22][23][24][25][26][27][28], co-adsorption of the gas molecules (meaning that the gas molecules can react directly with adsorbed species) [29], and the effect of using a periodic CO pressure [30][31][32][33].…”

Section: Introductionmentioning

confidence: 99%

Monte Carlo simulations of the critical properties of a Ziff-Gulari-Barshad model of catalytic CO oxidation with long-range reactivity

Chan

Rikvold

2015

Phys. Rev. E

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The Ziff-Gulari-Barshad (ZGB) model, a simplified description of the oxidation of carbon monoxide (CO) on a catalyst surface, is widely used to study properties of nonequilibrium phase transitions. In particular, it exhibits a nonequilibrium, discontinuous transition between a reactive and a CO poisoned phase. If one allows a nonzero rate of CO desorption (k), the line of phase transitions terminates at a critical point (k(c)). In this work, instead of restricting the CO and atomic oxygen (O) to react to form carbon dioxide (CO(2)) only when they are adsorbed in close proximity, we consider a modified model that includes an adjustable probability for adsorbed CO and O atoms located far apart on the lattice to react. We employ large-scale Monte Carlo simulations for system sizes up to 240×240 lattice sites, using the crossing of fourth-order cumulants to study the critical properties of this system. We find that the nonequilibrium critical point changes from the two-dimensional Ising universality class to the mean-field universality class upon introducing even a weak long-range reactivity mechanism. This conclusion is supported by measurements of cumulant fixed-point values, cluster percolation probabilities, correlation-length finite-size scaling properties, and the critical exponent ratio β/ν. The observed behavior is consistent with that of the equilibrium Ising ferromagnet with additional weak long-range interactions [T. Nakada, P. A. Rikvold, T. Mori, M. Nishino, and S. Miyashita, Phys. Rev. B 84, 054433 (2011)]. The large system sizes and the use of fourth-order cumulants also enable determination with improved accuracy of the critical point of the original ZGB model with CO desorption.

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“…Here, we therefore remove this phase by modifying the adsorption mechanism of the oxygen molecule, such that the two adsorbed atoms enter two next-nearest-neighbor sites instead of two nearest-neighbor sites [12,32]. Physically, such an effect could be due to exclusion or repulsion between nearest-neighbor adsorbed O atoms [33][34][35], or a tendency of the O atoms to move apart once they reach the surface due to their thermal energy, known as hot-atom adsorption [36][37][38]. This modification was already introduced in our previous study, Ref.…”

Section: Introductionmentioning

confidence: 99%

Model for the catalytic oxidation of CO, including gas-phase impurities and CO desorption

Rikvold

2013

Phys. Rev. E

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We present results of kinetic Monte Carlo simulations of a modified Ziff-Gulari-Barshad model for the reaction CO+O → CO2 on a catalytic surface. Our model includes impurities in the gas phase, CO desorption, and a modification known to eliminate the unphysical O poisoned phase. The impurities can adsorb and desorb on the surface, but otherwise remain inert. In a previous work that did not include CO desorption [G. M. Buendía and P. A. Rikvold, Phys. Rev. E, 85 031143 (2012)], we found that the impurities have very distinctive effects on the phase diagram and greatly diminish the reactivity of the system. If the impurities do not desorb, once the system reaches a stationary state, the CO2 production disappears. When the impurities are allowed to desorb, there are regions where the CO2 reaction window reappears, although greatly reduced. Following experimental evidence that indicates that temperature effects are crucial in many catalytic processes, here we further analyze these effects by including a CO desorption rate. We find that the CO desorption has the effect to smooth the transition between the reactive and the CO rich phase, and most importantly it can counteract the negative effects of the presence of impurities by widening the reactive window such that now the system remains catalytically active in the whole range of CO pressures.

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EXISTENCE OF A "HOT" ATOM MECHANISM FOR THE DISSOCIATION OF O₂ ON Pt (111) AND THE PHASE DIAGRAM OF CATALYTIC OXIDATION OF CO

Cited by 6 publications

References 19 publications

Comparison between different oxygen adsorption mechanisms for the catalytic oxidation of CO on a surface

Comparison between different oxygen adsorption mechanisms for the catalytic oxidation of CO on a surface

Monte Carlo simulations of the critical properties of a Ziff-Gulari-Barshad model of catalytic CO oxidation with long-range reactivity

Model for the catalytic oxidation of CO, including gas-phase impurities and CO desorption

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