Journal of Physical Chemistry, Vol.100, No.8, 3221-3226, 1996
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 out in its bistable region consisting of the thermodynamically controlled state which is characterized by a high Ce4+ concentration and the kinetically controlled state which shows low Ce4+ concentrations. Application of an electric current causes redox processes on the working electrodes. Inside the region of bistability a transition from the thermodynamic branch to the kinetic branch occurs in both the anodic and the cathodic reactors when the potential of the applied current exceeds certain threshold values. However, in the MB reaction a transition from the kinetic to the thermodynamic branch is not possible by the application of an electrical current. On the thermodynamic branch outside the bistability region, chemical oscillations are generated in both reactors when the electric current exceeds a threshold value. When the electric current is further increased, the oscillations give way to a steady state of a low Ce4+ concentration. After turning off the electric current the system returns to its original thermodynamic branch. On the kinetic branch at high flow rates the effect of the electric current on the redox potential is minimal. The experimental results are in good agreement with simulations using the NFT model provided that the effect of the electric current is specifically applied to the rate term for the bromine dioxide radical.