Chaotic dynamics in the three-variable kinetic model of CO oxidation on platinum group metals

The paper addresses the development of a simple three-variable kinetic model of CO oxidation on metallic catalysts under isothermal conditions and the numerical study of chaotic dynamics of the reaction rate. It is suggested that, at some concentrations of the adsorbed oxygen, a surface modification occurs and the reaction capability of adsorbed oxygen changes, so that the activation energy of the interaction between the adsorbed species increases sharply. Moreover, oxygen atoms can penetrate into the subsurface catalyst layer. At some critical values of the subsurface oxygen concentration, the catalyst surface reconstructs and the probability of oxygen adsorption decreases sharply. Based on these suggestions, a three-variable kinetic model of CO oxidation on the metals of the platinum group is developed, which has the hierarchy of characteristic times and one slow variable. For the purpose of studying the dynamics of the model, the one-parameter family of two-variable subsystems with fast variables is considered, and the steady states and periodic solutions of these subsystems were investigated. The conditions are described under which the dynamics of the model becomes chaotic by means of a cascade of period-doubling bifurcations or owing to complex multipeak oscillations.