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Sonoelektrochemia : wpływ ultradźwięków na przebieg procesów elektrodowych oraz ich praktyczne wykorzystanie w elektrochemii

Winkler K., Wysocka M.

Wiadomości Chemiczne

2002

[Z] 56, 11-12

895-930

Sonoelectrochemistry is the field of the research dealing with the influence of power ultrasound on electrochemical processes. The dominant effect of the ultrasound in electrochemical systems is the enhancement of mass transport by macrostreaming due to the propagation of an acoustic wave and microstreaming related to the acoustic cavitation phenomena and microjetts formation on the electrode surface. These effects are responsible for large enhancement of the current and significant modification of voltammograms recorded at stationary electrodes. In the presence of power ultrasounds voltammograms show steady-state sigmoidal shape with an oscillatory behavior. A simple planar diffusion layer model may be employed to analyze the current data. Ultrasound can also influence physical and chemical properties of electrode surface. Cavitation induced by ultrasound as well as shear forces can cause cleaning of the electrode surface and prevent adsorption and precipitation processes. Sonication can activate the electrode surface, too. High power ultrasound can also change the morphology of the electrode surface. Ultrasounds are succesfuly applied to a wide range of electrochemical technologies. There are frequently used in electrometalurgy for metal coating, electropolishing, electromachining, and electrochemical etching. The use of ultrasound allow eleiminate highly toxic compounds from the electroplating procedures. Ultrasound can significantly improve electrochemical synthesis processes. These improvements include enhancment diffusion and trerefore increase of yields and current efficiency, suppresed electrode fouling and alteration of reaction mechanism, and product selectivity control. Polymer films formed at the electrode surface in sonicated solution show better morrphology and mechanic properties. High rate of mass transfer under sonoelectrochemical conditions allows kinetic study of fast heterogeneous charge transfer processes and chemical steps coupled with rlectron transfer reaction. The application of ultrasound to analytical procedure can provide numerous benefits of which enhanced mass transport and in situ cleaning of the electrode are the most important. Sonoelectrochemistry analytical methods exhibit high sensitivity and good reproducibility. There are also less time consuming procedures comparison to conventional electroanalytical methods prformed under silent conditions. Ultrasound allows the formation of emmulsions in heterogeneous systems of immiscible organic and aqueous solvents without stabilizing agents simply by mechanical forces atributed to cavitation processes which arise at the liquid/liquid phase boundaries. Sonoelectrochemical is also used in nanotechnology for formation of nano-size metalic and non-metalic particles. The electrochemical study of electrode reactions of organic reagents in polar water solution can be carried out in these systems. Emulsions stabilized by ultrasound can be also used in quantitative analysis of water insoluble samples.