Nonlinear Self‐Organizing Kinetics in the Electrochemical Growth of Alumina Nanotube Arrays

Abstract

The nonlinear self‐organizing kinetics that occur during the electrosynthesis of porous anodic alumina (PAA) are investigated. It is first found that the ordered PAA nanoarray forms through the self‐organization of aluminum hydroxide colloids, rather than the traditional pitting‐corrosion mechanism. There is more than one parallel reaction path in the system, and a nonlinear feedback mechanism exists in one of them. Both the spatial periodicity of the nanoarray and the time periodicity of the current are dominated by a nonlinear reaction path during the self‐organization of the diffusion–reaction coupled system. The electrochemical growth mechanism is analyzed and dynamic Equations are established. The self‐catalysis effect of the condensed cationic intermediates on the hydrolysis and condensation of Al hydroxide is explained. This widely exists in the electro‐dissolution of various metals and plays a key role in electrochemical oscillation or self‐organization when the system is driven far from its equilibrium state by the electric field. The slow diffusion of the condensed cations in the gel is key for the formation of the nanoarrays, which provides new ideas for structure control during the synthesis of ordered nano‐oxides.

Continuous wet-process growth of ZnO nanoarrays for wire-shaped photoanode of dye-sensitized solar cell

“…When the diffusion coefficient of the activator is less than that of the repressor, periodic spatial structures could form through selforganization. Similar mechanism has been reported in metal electrooxidation processes [32]. During which, micelle-like condensation cations in the hydroxide gel system can act as the activator.…”

Electrochemical Oscillation during Electro-Synthesis of KMnO4under Highly-Alkaline Condition

“…H 2 O 2 + 2Fe(OH) 2 → 2Fe(OH) 3 [17] As is indicated by above experimental results, the periodic EO signal is then enhanced, 40 in a similar way as the Al electro-oxidation process. 41 Thus, the EO on the anode reveals a complicated but interesting electrochemical mechanism in the electro-synthesis of KMnO 4 under highly-alkaline and high-current condition. As is discussed above, the percentage of the power consumption due to the current-oscillation part in the total power consumption (power oscillation%) could be calculated via ( V a × I(t) × dt) / ( V a × I(t) × dt).…”

Influence of the Ligands in Cu(II) Complexes on the Oscillatory Electrodeposition of Cu/Cu2O

“…3−7 Differently from a standard step-by-step synthesis procedure, self-organized electrochemical structures arise without any external control or template-based support. 8 Nanostructured metallic multilayers, 9 magnetic nanopatterning, 10 switchable roughness surfaces, 11 and porous nanoarrays 12 are a few examples found through the use of this nonequilibrium synthetic method. Followed by the spontaneous assembly of the material constituents, temporal instabilities, such as excitability, multistability, and oscillations, are observed on the main variables that describe the system.…”

“…The synthesis of materials with novel physicochemical properties employing the controlled manipulation of their microstructure at the atomic level became a field based on solid-state chemistry. , As recently proposed, nevertheless, self-organization under far from equilibrium conditions can also be utilized as a promising and alternative synthetic method to create more complex materials in terms of structure and composition. − Differently from a standard step-by-step synthesis procedure, self-organized electrochemical structures arise without any external control or template-based support . Nanostructured metallic multilayers, magnetic nanopatterning, switchable roughness surfaces, and porous nanoarrays are a few examples found through the use of this nonequilibrium synthetic method. Followed by the spontaneous assembly of the material constituents, temporal instabilities, such as excitability, multistability, and oscillations, are observed on the main variables that describe the system .…”