Chemical Wave Propagation in the Belousov–Zhabotinsky Reaction Controlled by Electrical Potential

The Belousov–Zhabotinsky (BZ) reaction is an important experimental model for the study of chemical oscillations and waves far from the thermodynamic equilibrium. Earlier studies had observed that individual BZ microbeads can show both global oscillations and traveling waves, but failed to select these different dynamic states. Here, we report experiments, in which this control was achieved by an externally applied electrical potential. The spherical microbeads were first loaded with the catalyst, then immersed into a catalyst-free BZ solution, and finally placed onto a planar platinum electrode. For positive electrical potentials, we observed global oscillations, whereas negative potentials resulted in traveling waves. The spatio-temporal characteristics of these phenomena are discussed in relation to the activator, HBrO2, which is produced by an electrochemical reaction.