Bistability in catalytic reactions on the nm scale

We present Monte Carlo simulations of the bistable kinetics of CO oxidation occurring on nm-sized catalyst particles. The analysis is focused on the simplest case when reaction runs primarily on the (1 1 1) facets. Specifically, the catalyst particle is represented by a truncated triangular lattice. The lattice size, L, is varied from 100 down to 3. The model takes into account specifics of oxygen adsorption on the (1 1 1) face of fcc metals (in particular, oxygen adsorption on nearest-neighbour sites is prohibited). The results, obtained with a qualitatively realistic ratio of the rates of elementary reaction steps, indicate that the hysteresis in the reaction kinetics is nearly independent of L for L⩾10. For small lattices with L⩽5, the hysteresis disappears. The implications of these findings for interpretation of experimental data are briefly discussed.