Electrode polishing

Mechanical grinding and polishing

The first step treatment of the solid electrode surface is mechanical grinding and polishing to the degree of mirror surface. In particular, when an inerting layer and a strongly adsorbed layer are present on the electrode surface, mechanical treatment is necessary. (However, mechanical polishing will cause certain damage to the electrode, so please operate carefully.

The materials usually used for polishing electrodes are gold and steel grit, CeO2, ZrO2, MgO and alpha-Al2O3 powder and polishing liquid. During polishing, the polishing is always carried out in the order of decreasing particle size of the polishing agent. For example, the new electrode surface is roughly ground by sandpaper (2000# or 3000# sandpaper is recommended) and finely ground (5000# sandpaper is recommended), and then the alpha-Al2O3 foundation 1.5 is used. The particle size of 0.5 and 0.05 μm is polished in the shape of "8" on the polishing cloth, and the effect is very good. 2-3 minutes each time, repeat three times, until clean. After thorough washing with ethanol, dilute acid and water, a smooth, clean, fresh electrode surface was obtained.

Chemical and electrochemical treatment

After the solid electrode is polished, it is followed by chemical, especially electrochemical treatment, which is more commonly used to clean and activate the electrode surface [1]. Electrochemical methods commonly use strong mineral acids or neutral electrolyte solutions, and sometimes weak compatible buffer solutions (such as acetic acid and phosphoric acid) to polarize under constant potential, constant current, or cyclic potential scanning (such as 1.8 ~-0.4V VS. Ag/AgCl in 0.5mol/LK2SO4), depending on the potential of the scanning potential termination, oxidized, reduced or clean electrode surfaces can be obtained [2-4]. Electrochemical method can also be directly in the test solution for electrode treatment, the method is simple and easy. When the carbon electrode is oxidized at a high positive potential or a high anodic current, many oxygen-containing groups will be produced on the surface [4-6], and the electrochemical treatment of the carbon electrode by anodization can lead to the improvement of the sensitivity and selectivity of the measurement. As the charge increases, the concentration of phenol groups on the surface increases and the basis decreases [4]. If the charge is too large, it is easy to cause a carbon oxide layer and lose the redox activity. However, the carbon electrode in alkaline solution at positive potential polarization [7](pH13,+1.2V vs. SCE) treatment for 5 minutes, can inhibit the formation of thick carbon oxide film, reduce the double layer capacitance, and eliminate the adsorption effect of solvent.

For the treatment of platinum electrodes, if the chemical and electrochemical methods are combined, better results can often be obtained [8]. That is, anodic polarization is performed first, then the oxide layer is removed by immersion in a newly prepared solvent (the solvent can be organic solvent or inorganic solvent, dilute nitric acid, cold aqua regia, etc., please treat it as appropriate according to the actual situation), washed with water and then cathodic polarization is performed, and the later potential is kept at zero volt to remove adsorbed hydrogen.

[1] I.M.Kolthoff,N.Tanaka,Anal.Chem.,26,632(1954).

[2] R.N.Adams, "Electrochemistry at Solid Electrodes", Marcel Dekker,New York(1969).

[3] J.-X.Feng ,M.Brazell,k.Renner,R.kasser,R.N.Adams,Anal.Chem.,59,1863(1987).

[4] J.Mattusch,K.H.Hallmeier,K.Stulik,V.Pacakova,Electroanlysis,1,405(1989).

[5] J.Wang,M.S.Lin,Anal.Chem.,60,499(1988).

[6] L,J.Kepley,A.Bard,Anal.Chem.,60,1459(1988).

[7] D.M.Anjo,M.Kahr,M.M.Khodabakhsh,S.Nowinski,M.Wanger,Anal.Chem.,61,2603(1989).

[8] J.W.Bixler,S.Bruckenstein,Anal.Chem.,37,791(1965).