Electrochemical Cells

Electrochemical cells were usually called as galvanic or voltaic cells, Alessandro Volta invented voltaic pile which was the first modern electrical battery, it was invented in 1800 and the major stimulus for to produce this constant source of current electricity was provided by Luigi Galvani, however when Galvani concluded that muscles produces electricity when twitched and touched by two metals, it was Volta who opposed by reasoning that the electricity was metallic, which was caused by interaction of metals, the commonly used batteries nowadays consists of electrochemical cells. An electrochemical cell consists of two half cells having a pair of electrodes and electrolyte each.

Electrochemical cells

The main aim of an electrochemical cell is to generate or to utilize the electrical energy produced by a chemical reaction, these reactions are generally oxidation-reduction mainly referred as redox reactions, where the electrons are transferred from one chemical substance that is being oxidized to the other that is being reduced, and these cells are generally called galvanic or voltaic cells, one of the most common example is a normal 1.5v cell, which is regularly used in day to day life appliances such as TV remotes, watches etc. Electrochemical cells convert electrical energy into chemical energy and vice-versa.

Types

Galvanic cell or Voltaic cell

This cell is named after Luigi Galvani and Alessandro Volta, it converts chemical energy into electrical energy, some of the components of the Galvanic cells are Electrodes (a combination of anode and cathode), Electrolytes (a component helping in movement of ions), Salt bridge (a connection between two cells), Voltmeter (a device used to measure the voltage), the working of the galvanic cell is as follows, Once the redox reaction starts, the oxidation occurs at anode and reduction occurs at cathode and the electrons generated in oxidation half-cell travel to the reduction half-cell, and with time the size of cathode rod increases. The electromotive force depends upon movement of electrons thus both electrolytes and electrodes.

Electrolytic cell

This cell other than the galvanic cell is completely opposite; this cell is a type of electrochemical cell that provides electrical energy so that a non spontaneous redox reaction may occur, electrolysis means breaking which indicates generally breaking or decomposition takes place. A rechargeable battery is the most common example of an electrolytic cell. An electrolytic cell is generally made of three components the cathode, the anode and electrolyte, these cells typically consists of two metallic conductors (electrodes) in contact with an electrolyte, the negative ions migrate to the positive electrode (anode) and transfer one or more electrons to it, also becoming new ions or neutral particles. In our day to day lives, oxygen and hydrogen gas are obtained from electrolysis from electrolytic cells, electrolytic cells are also used for electroplating.

Electrochemical cells

Working

Electrochemical cells are divided into two half cells, the oxidation and reduction will take place in two separate beakers, one beaker contains copper plate dipped into 0.1 M copper sulfate solution and the other beaker contains zinc plate dipped into 0.1 M zinc sulfate solution and these are connected with the help of a salt bridge, and this bridge is filled with a solution of electrolyte as KCl (electrolyte doesn’t undergo any chemical change under chemical process), the ends of this bridge are covered with wool or cotton, now the reaction occurs as following :

These two electrodes are connected by a copper wire and we could check the reading in ammeter as it indicates that the current is flowing.

The oxidation half reaction occurs at anode:  Zn(s) → Zn2+ (aq) + 2e–

The reduction half reaction occurs at cathode: Cu2+ (aq) + 2e– → Cu(s)

Anode is negative electrode and cathode is positive electrode, the movement of electron is from anode to cathode, the Zn2+ ions are dissolved in the anode compartment, while the Cu2+ ions are deposited at the cathode and the neutrality of these two solutions is maintained by the salt bridge by providing cations and anions.

Now the complete cell reaction becomes:  Zn(s) + Cu2+(aq) → Zn2+(aq) + Cu(s) and thus energy in the electrical form is generated in such electrochemical cells.

Conclusion

The movement of ions occurs because the electric current in the circuit provides a potential difference between two electrodes; oxidation is loss of electrons at anode.