Stochastic fluctuations or noise in complex dynamical systems with strong nonlinearities give rise to unexpected and new ordered phenomena. Chemical reactions on solid surfaces exhibit non-linear behavior, such as bistability, self-sustained kinetic oscillations, chaos and spatiotemporal patterns. For this reason, understanding the influence of noise on the complex behavior of catalytic surface reactions has become a challenge in recent years. In this talk a theoretical study of external noise on two minimalistic models for the catalytic CO oxidation on surface reactions is presented. We show that those deterministic models present kinetic bistability. We also show that in or near the region where bistability is observed a time scale separation between the oxygen coverage and the CO coverage exists. It allows a reduction of the models by the adiabatically elimination of the fast oxygen coverage (quasi-steady state approximation). Then, stochastic models are constructed by superposing noise on the fraction of CO in the constant gas flow directed at the surfaces. Reduced one variable stochastic models can also be found after the adiabatic elimination of oxygen coverage. This reduction allows us to analyze theoretically the interplay between external noise and the kinetic bistability. Firstly, it is reported the phenomena of noise-induced shift of steady states. Secondly, it is shown evidence for a transition to a bistable state induced by noise. The analytical results are compared with simulations of the original two variable stochastic reaction systems.