Bifurcations of spatiotemporal stripe patterns formed by Ag/Sb co-electrodeposition

Various spatiotemporal patterns, which are similar to those in reaction–diffusion systems, are studied on metal electrodes formed by Ag/Sb co-electrodeposition. To elucidate the characteristics of these spatiotemporal patterns, we investigated the dependence of several kinds of propagating stripe patterns on the current density, using an optical microscope. Based on the experimental results, a phase diagram of several kinds of propagating stripe patterns against current density was completed. In addition, we discovered that the bifurcations to two different stripe patterns occurred on one electrode at the initial stage of the electrodeposition process. The combination of the two bifurcated patterns changes depending on the current density. However, each pattern sustains its inherent value of the stripe wavelength for all current densities at which it could emerge on an electrode surface. The inherent stripe wavelengths of patterns show a difference in wavelength of one or two orders. The inherent values of stripe velocities of uniaxially propagating stripe patterns were also observed to have a one order difference. However, the calculated frequencies fp (i.e., stripe velocity/stripe wavelength) of uniaxially propagating stripe patterns were found to be nearly the same. Finally, two bifurcated patterns at the initial stage are unified into one pattern with a longer wavelength with time, independently of their frequencies. This characteristic is significantly different from that of patterns in Belousov–Zhabotinsky (BZ) reaction exemplifying the reaction–diffusion system. The marked difference from the BZ reaction system clearly indicates that this system is a new system that should be distinguished from the conventional system.