OSCILLATORY INSTABILITIES DURING FORMIC-ACID OXIDATION ON PT(100), PT(110) AND PT(111) UNDER POTENTIOSTATIC CONTROL .2. MODEL-CALCULATIONS

A kinetic model is developed for the electrocatalytic oxidation of for mic acid on Pt under potentiostatic control. The model development pro ceeds stepwise via a simple model of the electrocatalytic CO oxidation . The full model consists of four coupled, nonlinear ordinary differen tial equations. The scanned and stationary current/outer potential (I/ U) behavior, stationary current oscillations, two-parameter bifurcatio n diagrams and stirring effects are simulated using realistic model pa rameters. The numerical findings are found to be consistent with the e xperimental results given by Strasser et al. The model reproduces peri od-1 as well as mixed-mode oscillations. Furthermore, a mechanistic an alysis of the model was performed: two suboscillators are identified w hose characteristics allow a plausible interpretation of the observed dynamics. After a classification of the suboscillators into previously described categories, an attempt is made to identify the minimal mech anistic requirements for electrochemical current oscillations. (C) 199 7 American Institute of Physics.