The Formation and Spatiotemporal Progress of the pH Wave Induced by the Temperature Gradient in the Thin-Layer H₂O₂–Na₂S₂O₃–H₂SO₄–CuSO₄ Dynamical System

Abstract

The H2O2-S2O3(2-)-H(+)-Cu(2+) dynamical system exhibits sustained oscillations under flow conditions but reveals only a single initial peak of the indicator electrode potential and pH variation under batch isothermal conditions. Thus, in the latter case, there is no possibility of the coupling of the oscillations and diffusion which could lead to formation of sustained spatiotemporal patterns in this process. However, in the inhomogeneous temperature field, due to dependence of the local reaction kinetics on temperature, spatial inhomogeneities of pH distribution can develop which, in the presence of an appropriate indicator, thymol blue, manifest themselves as the color front traveling along the quasi-one-dimensional reactor. In this work, we describe the experimental conditions under which the above-mentioned phenomena can be observed and present their numerical model based on thermokinetic coupling and spatial coordinate introduced to earlier isothermal homogeneous kinetic mechanism.

On the Phase Shifts in the Dynamics of the H2O2–Na2S2O3–H2SO4–CuSO4 Oscillator Revealed by Comparison of Potentiometric Responses of Different Indicator Electrodes

“…One should also note that, as observed by us, the amplitudes of the oscillations of the readings of the pH and Pt electrodes were somewhat smaller than those reported by Orbán et al , but this discrepancy can be due to different concentrations of CuSO 4 in the feeding stream. Another reason can be a relatively high sensitivity of this reaction kinetics to temperature—recently we reported that the higher temperature, the smaller the observed amplitudes. Furthermore, concerning the bifurcation limits, in the model the onset of the sustained oscillations occurs at k 0 approximately twice greater than in the experiment.…”

Photoinduced Oscillations and Pulse Waves in the Hydrogen Peroxide–Sulfite–Ferrocyanide Reaction

“…30,31 Phase waves were also obtained by coupling a temperature gradient to the H 2 O 2 −Na 2 S 2 O 3 −H 2 SO 4 −CuSO 4 reaction in a reaction− diffusion medium. 32 Various dynamical behaviors are well understood in pH oscillators. 33,34 However, few studies have been performed on the light effect on spatiotemporal patterns based on pH oscillatory systems.…”

“…With the discovery of pH oscillations in homogeneous media, self-organizing pH patterns have been obtained using a systematic design method . Traveling wave and stable patterns have been observed supported by the HPSF reaction. , Phase waves were also obtained by coupling a temperature gradient to the H 2 O 2 –Na 2 S 2 O 3 –H 2 SO 4 –CuSO 4 reaction in a reaction–diffusion medium . Various dynamical behaviors are well understood in pH oscillators. , However, few studies have been performed on the light effect on spatiotemporal patterns based on pH oscillatory systems.…”