Electrode

William Whewell coined the term electrode, which was derived from the Greek words Elektron, which means “amber,” and hodos, which means “a way.” The electrophore, which was used to study static electricity, was an early version of an electrode that was used to conduct experiments. Johan Wilcke is credited with inventing the term. In order to make the concept more understandable, an electrode can be defined as a point where current enters and exits the electrolyte. It is worth noting that an electrode does not necessarily have to be made of metals.

Categories of electrodes

Generally speaking, electrodes can be divided into two categories: reactive electrodes and inert electrodes.

Types are either inert or reactive, with the former not participating in any reactions and the latter taking an active role in them.

Platinum, gold, graphite (carbon), and rhodium are just a few of the inert electrodes that are commonly used.

Zinc, copper, lead, and silver are just a few of the reactive electrodes available.

The anode, on the other hand, is the point at which the current enters during the oxidation reaction. The electrodes in electrochemical cells serve a critical function in that they transport produced electrons from one half-cell to another, resulting in the generation of an electrical charge.

Applications of electrodes

The primary function of electrodes is to generate electrical current and conduct it through non-metal objects in order to fundamentally alter them in a variety of ways, a process known as electrolysis. Conductivity can also be measured with the help of electrodes. Among the other applications are:

1. In addition to different battery types, electroplating and electrolysis, welding, cathodic protection, membrane electrode assembly, for chemical analysis, and the Taser electroshock weapon are all applications for electrode technology. 
2. Electrodes are also used in the medical field for ECG, ECT, EEG, and defibrillators, among other things. The electrophysiology techniques used in biomedical research are made possible by the use of electrodes.

Difference between Cathode and Anode 

At the electrodes of an electrochemical cell, reduction and oxidation reactions take place simultaneously. In electrochemistry, the cathode refers to the electrode at which reduction takes place. The anode is where the oxidation takes place.

The direction in which a cell is operating determines whether an electrode acts as a cathode or an anode in that cell.

When a cell is switched from operating galvanically (i.e., producing energy like a battery) to operating electrolytically (i.e., requiring energy to be supplied to the cell), the cathode becomes the anode and vice versa.

Analytical Chemistry Electrode Examples 

Amorphous carbon, gold, and platinum are examples of materials that are commonly used as electrodes in analytical chemistry applications. Glass electrodes are frequently used in pH measurements; in this application, the glass has been chemically doped to be selective to hydrogen ions, making it an excellent choice for this application.

When it comes to batteries, depending on the type of battery, there are a variety of electrodes to choose from.

Lithium-ion batteries are based on the use of lead electrodes.

Zinc-carbon batteries are made up of zinc and amorphous carbon electrodes, which are combined to form a battery.

Lithium polymer batteries have electrodes that are composed of a solid polymer matrix in which lithium ions can move and act as charge carriers. Lithium polymer batteries are used in electric vehicles.

Electrolysis is a technique for converting salts and ores into metals that uses electrical energy.

It is used in the Hall-Heroult process to extract aluminium metal from aluminium oxide, and both the anode and the cathode are made of graphite in order to do so.

Electrolysis is used to produce sodium metal, which is done with a carbon anode and an iron cathode.

Pattern of Electrodes

It has been discovered that the electrode pattern or configurations have an impact on the ER effect, depending on the type of ER fluids present between the electrodes. When used in place of smooth surface electrodes, various patterned electrodes such as a honeycomb-shaped metallic mesh structure, a concentric circle configuration, and a radial shape can typically increase the ER effect by as much as 2.3 times on average. 

At 4 kV/mm, the honeycomb electrode generates an ER effect that is nearly twice as strong as that produced by the electrode with a smooth surface. Further research has revealed that the size of the hole in the honeycomb pattern has an effect on the ER effect. The shear stress and yield stress of a composite particle/silicone oil suspension as a function of the metallic mesh size covered on the electrode surface when subjected to various electric fields. It appears that when the mesh size is approximately 100 m and the electric fields range from 0.66 to 3.33 kV/mm, the maximum shear stress is obtained. The shear stress measured with the metallic net electrode is approximately 1.8 to 2.3 times greater than the shear stress measured with the smooth electrode, depending on the method used. This may be due to the non-uniformity of the electric field generated by the patterned electrode, as well as the reduction in shearing slip caused by the rough surface of the electrode, which may be responsible for the enhanced ER effect.

The polarisation of the electrode

The accumulation of charge on electrode surfaces, as well as the formation of electrical double layers, is responsible for the polarisation of the electrodes themselves. Whenever an alternating current field is applied, the ions in the suspension should be distributed in a double layer as described by Debye and Hückel; whenever an alternating current field is applied, the ions in the suspension should respond to the charge on the electrodes, with their response being delayed by the drag force from the liquid medium. As a result, the frequency of the applied electric field has an effect on the double layer, because the charges on the electrodes oscillate at a faster rate than the movement of the ions. High frequency causes the ions to become incapable of moving quickly enough to form the double layer, and as a result the electrode polarisation is lost. When the frequency is low, the electrode polarisation becomes significant, resulting in a very large dielectric constant. The dielectric constant of water is 78. At low frequencies below 200 Hz, on the other hand, the dielectric constant increases to more than 10000 as the frequency decreases to around 10 Hz, which is caused by the electrode polarisation causing the frequency to decrease.

Conclusion

Therefore, we can finally conclude that electrodes can be divided into two categories: Reactive electrodes and Inert electrodes. The primary function of electrodes is to generate electrical current and conduct it through non-metal objects in order to fundamentally alter them in a variety of ways, a process known as electrolysis. Conductivity can also be measured with the help of electrodes.