Electrodes and Electrode Preparation

In studies which focus on the redox properties of immobilized microparticles, electrode preparation and electrolyte composition are to be carefully considered. Almost any kind of solid electrode may be applied in order to investigate the redox properties of immobilized solid microparticles. However, attention must be drawn to possible catalytic properties of the electrode with respect to the reactions to be studied, and reactions of the electrolyte, which may or may not accompany the reactions of the solids. Also, the surface hardness of the particular electrode should be kept in mind. For example, a hard electrode will allow soft or flake-like solids to be attached while a smooth and soft electrode will preferably be applied in studies of hard materials to obtain a good embedding of the microparticles in the soft surface. 

The method involves attaching an ensemble of solid microcrystalline particles to the surface of a suitable electrode. The electrode with the so immobilized solid is then transferred to an electrolyte solution and investigated either purely electrochemically or by additional methods. 

Carbon electrodes probably exhibit the most convenient properties in that they combine a large potential window in either aqueous or non-aqueous solutions with almost any desirable size and hardness, not to mention availability and price. 

Hardness of an electrode can often be related to the ability of a solid compound to adhere to an electrode surface. For example, fairly soft, flake-like materials, such as many organic compounds, will preferably adhere to a hard surface, e. g., that of a glassy carbon (GC) electrode, while hard solids such as oxides or ores will adhere to a soft surface such as that of a paraffin-impregnated graphite electrode (PIGE). 

Glassy carbon electrodes come in different hardnesses, but are generally the hardest non-diamondlike carbon electrodes one can get. Care should be taken when roughening a glassy carbon electrode because additional complications may arise. For example, it has been observed that an electrolyte film can separate the glassy carbon surface from the immobilized particles. This can give rise to special phenomena associated with the electron transfer from the carbon to the sample particles [2]. 

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