Modeling of Carbon Monoxide Oxidation on Gold Nanoparticles: Is There Oscillatory Mode?
The stability conditions for mathematical models of carbon monoxide oxidation on the surface of gold nanoparticles are investigated. The cases of reaction mechanisms of one-step and step-by-step transformation of reagents are consecutively considered. Usi
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Abstract. The stability conditions for mathematical models of carbon monoxide oxidation on the surface of gold nanoparticles are investigated. The cases of reaction mechanisms of one-step and step-by-step transformation of reagents are consecutively considered. Using the stability analysis by Lyapunov method, it is shown that models which take into account the possibility of structural changes of the catalyst surface can predict the occurrence of oscillatory mode in the system as a result of Hopf instability.
Keywords: Reaction of catalytic oxidation oxidation · Gold nanoparticles
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· Modeling of CO
Introduction
Studies of catalytic carbon monoxide (CO) oxidation is one of the most important problems in modern science [1]. Technologically, this process is essential for many applications: car exhaust emissions control, air purification, carbon dioxide lasers and sensors etc. Theoretically, it is one of the simplest catalytic reactions and is widely used as a model system for understanding heterogeneous catalysis. Mathematical modeling of CO oxidation reaction on the surfaces of heterogeneous catalysts has evolved much since prediction of the oscillatory mode of this reaction on the surface of platinum (Pt) group catalysts in the works of Ertl [2]. However, Pt catalysts are expensive and temperatures at which CO oxidation reaction takes place are high (∼500 K). These disadvantages led to the study of new structural elements of the catalyst surface, in particular from the group of noble metals. In the late 1980s, Haruta and co-workers first showed that small particles of gold (Au) can be active catalysts for the low-temperature CO oxidation [3]. Initially, the high activity of gold-based catalysts was considered to be caused by the type of composite substrate – the metal oxides (reducible: TiO2, NiO, Fe2O3 or irreducible: Al2O3, MgAl2O4). However, after detailed investigations, c The Author(s), under exclusive license to Springer Nature Switzerland AG 2021 N. Shakhovska and M. O. Medykovskyy (Eds.): CSIT 2020, AISC 1293, pp. 512–521, 2021. https://doi.org/10.1007/978-3-030-63270-0_34
Modeling of Carbon Monoxide Oxidation on Gold Nanoparticles
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it was found that the very active catalysts were small gold nanoparticles of about 2–4 nm in size [4], dispersed on these oxides. The purpose of this work is to investigate the stability conditions for mathematical models of CO catalytic oxidation on the surface of gold nanoparticles. A similar problem was solved for some mathematical models of CO oxidation on the Pt-catalyst surface [5,6], for which the stability regions of reaction and conditions for Hopf [7] and Turing [8] instabilities to arise were investigated. By analogy with Pt, we assume that oxidation reaction occurs according to the Langmuir-Hinshelwood mechanism [9]. That is, interaction between the reactants is possible only in the adsorbed layer, where there are free active sites of two different types. The reaction scheme consists of two elementary steps: the reversible molecular adsorption of CO and ox
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