MODELING TEMPORAL KINETIC OSCILLATIONS FOR CO OXIDATION ON PT(100) - THE (1X1)-CO ISLAND GROWTH-RATE POWER-LAW MODEL

An improved model which accurately reproduces the observed kinetic oscillations for CO oxidation on Pt{100} is presented. It incorporates a strongly non-linear power law for the (1 x 1)-CO island growth rate from the stable hex phase with an apparent reaction order of about four in the local CO coverage on the hex phase. This experimentally determined power law replaces the formerly assumed first-order process. Calculations for the CO + O2 system reveal that the oscillatory behaviour is very sensitive to the assumed value for the reaction order; values less than three do not produce the characteristic oscillatory behaviour. Hysteresis between two rate branches is demonstrated in calculations of the steady states as a function of (1 x 1) surface area; these calculations provide a ready means of interpreting the kinetic oscillations.