Gloria Buendia
Department of Physics, Universidad Simon Bolivar, Caracas, Venezuela
Consortium of the Americas for Interdisciplinary Science
University of New Mexico, Albuquerque (USA)

Response of a Catalytic Reaction to Periodic Variation of the CO Pressure:
Increased CO₂ Production and Dynamic Phase Transition

We present a computational study of the dynamic behavior of a Ziff-Gulari-Barshad model of CO oxidation with CO desorption on a catalytic surface (CO + O₂ → CO₂) .  Below a critical desorption rate the model exhibits a non-equilibrium, first-order phase transition between low and high CO coverage phases.  We measure the lifetimes of the metastable phases on each side of the transition line and find that they are strongly dependent on the direction of the transformation. Inspired by this asymmetry, we subject the system to a square-wave periodic external pressure variation, with parameters that  can be tuned to enhance the catalytic activity.  This far-from-equilibrium driven system undergoes a dynamic phase transition between a CO2 productive phase and a nonproductive one. Near this transition the system experiments a significant enhancement of its catalytic activity, well beyond its maximum value under constant pressure conditions-a result that we believe could be exploited to develop novel ways to increase the efficiency of catalytic reactions.