Electrochemical Cells

Voltaic or galvanic cells generate an electric current, whereas electrolytic cells trigger chemical reactions like electrolysis.

An electrolytic cell is an electrochemical cell that uses electrical energy to drive a non-spontaneous redox reaction. Electrolysis—the Greek word lysis meaning “to break up”—is a technique used to degrade chemical molecules.

An electrochemical cell is a device that uses electricity to produce electricity. A simple 1.5-volt electrochemical cell is an example of an electrochemical cell used to power a variety of electrical equipment such as digital cameras, clocks, and AC remote controls.

We’ve assumed that the reactants are in close physical proximity in most of our chemical reaction descriptions. Acid-base reactions, for example, are commonly performed in a single phase, such as a liquid solution, with the acid and base spread throughout.

Voltaic and Galvanic cells are two types of cells that may create electricity through chemical reactions. Electrolytic cells are those that allow chemical reactions to take place when an electric current flows through them.

The chemical energy released during the redox process is converted to electrical energy by the electrochemical cell. For example, when the concentration of Zn2+ and Cu2+ ions is unity (1 mol dm–3), it has an electrical potential of 1.1 V.

Zn(s) + Cu2+(aq) → Zn2+(aq) + Cu(s)

Electrochemical Cell Classification

In an electrochemical cell, reactions take place at the cathode or anode. The following are some of the most essential characteristics of the cathode and anode: 

Cathode

• A positive (+ve) sign is used to indicate it.
• Here, the electrons are absorbed.
• A reduction reaction takes place.
• The electrons are displaced from the anode to the cathode.

Anode

• A negative(-ve) symbol is used to represent it.
• This is where the electrons are released.
• The oxidation reaction takes place.
• The anode’s electrons are displaced out.

Different kinds of electrochemical cells

There are two types of main cells and secondary cells.

• [Voltaic cells] Galvanic cells

• Cells that are electrolytic

There are several distinctions between Voltaic and Electrolytic cells, some of which are listed below:

Galvanic cells

• Chemical reactions can be used to generate electricity in voltaic cells.
• In voltaic cells, chemical reactions can be exploited to generate energy.
• Spontaneous reactions take place in these cells.
• The cathode is positively charged, while the anode is negatively charged in these cells.
• The oxidation process occurs at the anode, whereas the reduction process occurs at the cathode in these cells.
• Chemical reactions are used to generate electrical energy.
• Salt bridges are used to connect half-cells in other containers.
• An oxidation process occurs with the electrons generated from the species.

Electrolytic cells

• Chemical reactions are carried out in electrolytic cells using electric currents.
• Electrical energy is converted into chemical energy by electrolytic cells.
• Non-spontaneous responses take place in these cells.
• The anode in these cells is positively charged, whereas the cathode is negatively charged.
• The oxidation process occurs at the cathode, while the reduction process occurs at the anode in these cells.
• Electrical energy creates a chemical reaction with the help of an external source.
• In an electrolyte solution, electrodes are placed in the same containers.
• The electrons come from a battery or some external source.

Primary Cells

Primary cells are galvanic cells that are “single-use” or “use and discard,” and they cannot be recharged. Therefore, the events that occur in the main cell are unstoppable.

• The reactants are used to generate electrical energy, and the cell stops producing current once the reactants are depleted.
• Primary cells have high internal resistance and are very cost-effective.
• Dry cells and alkaline batteries are two examples.

The following are the cell reactions:

Zn(s) → Zn2+ + 2e– (Anode) 

MnO2 + NH4+ + e–→ MnO(OH) + NH3 (Cathode)

Secondary Cells

“Rechargeable” cells are another name for secondary cells. It signifies that the cell has a reversible response, which may be utilised as both galvanic and electrolytic cells.

• Secondary cells are robust and complex by design.
• Secondary cells are expensive and have low internal resistance.
• Lead storage batteries and nickel-cadmium storage cells are two examples.

The following are the cell reactions:

 Pb(s) + SO42–(aq) → PbSO4(s) + 2e– (Anode)

PbO2(s) + SO42–(aq) + 4H+(aq) + 2e– → PbSO4 (s) + 2H2O (l) (Cathode)

Overall cell reaction: Pb(s) + PbO2(s) + 2H2SO4(aq) → 2PbSO4(s) + 2H2O(l) 

Cell Potential and Half-Cells

A half cell is one of the electrochemical cells with two electrodes.

• Electrochemical cells are made up of two halves, each of which has an electrode immersed in an electrolyte.
• The half-cells are joined by a salt bridge that rises from the platform and seeks to make ionic contact between them without allowing them to mix.
• Take a filter paper dipped in potassium nitrate or sodium chloride solution as an example of a salt bridge.
• The electrode potential describes the tendency of an electrode in contact with an electrolyte to lose or absorb electrons.

Electrochemical Cells in Action

• Torches, digital timepieces, military applications, corrosion prevention, and other applications use electrochemical cells.
• Electrolytic cells are used to manufacture high-purity lead, zinc, aluminium, and copper.
• They use it to look for trace levels of metal ions in a solution.
• Fuel cells are a type of electrochemical cell that produces clean energy and is employed in various distant areas.
• Metallic sodium may be recovered from molten sodium chloride by running an electric current across it in an electrolytic cell.

Conclusion

There are many applications for electrochemical cells. A galvanic cell is used as the battery that we use today. The best example is the batteries that we use in torch lights, TV remotes, etc. Batteries are used in a variety of ways. Unlike many other electrochemical storage systems, lithium-ion (Li-ion) batteries have a wide range of electrode materials to choose from, making this a rich, complicated, and ever-flexible technology with constant performance advancements and a large number of parameters to tune.  Recently electrochemical cells were found to be used as lights. The light-emitting electrochemical cells are discovered. They consume low energy and are luminous with good efficiency.