ABSTRACT
The catalytic self-poisoning and bond-breaking selectivity at steps in the decomposition of ethylene on the stepped Ni (111) surfaces have been systematically investigated using the kinetic Monte Carlo (KMC) simulations, in which both the high reactivity of the step edge and the relative increase in reactivity of the dissociation (the C-C bond-breaking) reaction pathway at the step edge were incorporated. Our simulations definitely indicated that at the low temperature (T = 300 K), the catalytic self-poisoning at the steps dominates the ethylene decomposition. It was found that a small brim of the decomposed ethylene is formed at the upper step edges. However, the ethylene decomposition at the high temperature (T = 500 K) leads to a continuous growth of the carbidic islands even after the steps were self-poisoned. Importantly, the KMC simulations not only revealed the specific role of the steps in the bond-breaking selectivity in detail, but also provided the quantitative performance how the bond-breaking selectivity can be easily controlled by blocking the steps with Ag atoms at various temperatures. Interestingly, these results are in excellent agreement with the recent experiments. Therefore, our studies have had a clear and detailed insight into the microscopic process of the ethylene decomposition on the stepped Ni (111) surfaces, and the proposed method could be expected a powerful tool to design new and high-effective catalysts at the nanometer scale.
