Space and time correlations in a dissipative structure emerging in an electrochemical system with a cation-exchange membrane

The mechanism of electromasstransfer in a system containing a cation-exchange membrane at a current density exceeding the limiting diffusion current is studied by analyzing the electric potential fluctuations. An experimental setup is designed for measuring fluctuations simultaneously at 16 points in a galvanostatic mode. The fluctuations are found to form in a near-membrane diffusion layer of electrolyte depleted of carriers. As the current density increases, spectra of resonance fluctuations turn into flicker-noise spectra; this process is studied in great detail. Use of space and time difference moments for processing noise signals allowed us to estimate such parameters as the correlation time, space correlation length, and components of the propagation velocity for perturbations in the dissipative structure forming in the membrane system. The data point to the formation of convective flows thermally induced in a diffusion layer of electrolyte under the action of Joule heating at a current density approaching a limiting value.