KINETIC OSCILLATIONS AND HYSTERESIS PHENOMENA IN THE NO-2 REACTION ONRH(111) AND RH(533) - EXPERIMENTS AND MATHEMATICAL-MODELING(H)

Interesting kinetic phenomena, such as multiple steady states and kine tic oscillations recently found in the NO+H-2 reaction over Rh(533) an d Rh(111) single crystal surfaces in the 10(-6) mbar pressure range ha ve been studied by means of experiments and computer modeling. A mathe matical model, consisting of five ordinary differential equations and taking into account the lateral interactions in the adlayer, has been developed for simulating the NO+H-2/Rh(533) and NO+H-2/Rh(lll) reactio ns. The simulation results make it possible to explain in detail the u nderlying reasons for the experimentally observed complex dynamic beha vior, In particular, the kinetic oscillations and their properties hav e been reproduced. It was found that accumulation of NHads species, wh ich serves as an intermediate in the pathway of NH3 production, is an important step in the oscillatory mechanism, In addition, the same mat hematical model is able to successfully reproduce the experimental dat a concerning temperature programmed desorption (TPD) spectra, hysteres is phenomena, and the dependence of selectivity upon temperature and r eactant partial pressures. Lateral interactions in the adlayer are sho wn to play a crucial role in the adequate simulation of the experiment al observations. (C) 1996 American Institute of Physics.