EFFECT OF ELECTRIC-CURRENT IN THE MINIMAL BROMATE REACTION

Experiments and calculations of two electrically coupled flow reactors are presented in which the minimal bromate (MB) reaction is carried o ut in its bistable region consisting of the thermodynamically controll ed state which is characterized by a high Ce4+ concentration and the k inetically controlled state which shows low Ce4+ concentrations. Appli cation of an electric current causes redox processes on the working el ectrodes. Inside the region of bistability a transition from the therm odynamic branch to the kinetic branch occurs in both the anodic and th e cathodic reactors when the potential of the applied current exceeds certain threshold values. However, in the MB reaction a transition fro m the kinetic to the thermodynamic branch is not possible by the appli cation of an electrical current. On the thermodynamic branch outside t he bistability region, chemical oscillations are generated in both rea ctors when the electric current exceeds a threshold value. When the el ectric current is further increased, the oscillations give way to a st eady state of a low Ce4+ concentration. After turning off the electric current the system returns to its original thermodynamic branch. On t he kinetic branch at high flow rates the effect of the electric curren t on the redox potential is minimal. The experimental results are in g ood agreement with simulations using the NFT model provided that the e ffect of the electric current is specifically applied to the rate term for the bromine dioxide radical.