A Case Study on Electrolysis

Electrolysis is the process of passing a direct electric current through an electrolyte, causing chemical reactions and material degradation at the electrodes.

An electrolyte, electrodes, and an external power source, among other things, are required for electrolysis. To prevent the products from diffusing to the opposite electrode, a partition (such as an ion-exchange membrane or a salt bridge) can be used.

Electrolyte:

The electrolyte is a chemical component that includes free ions that conducts electricity (An ion-conducting polymer, solution, or ionic liquid substance, for example). When the ions are not mobile, as they are in most solid salts, electrolysis is impossible. The following steps are used to make a liquid electrolyte:

Solvation : The reaction of an ionic substance with a solvent (such as water) to produce mobile ions is known as solvation.

By heating an ionic substance, it melts.

The electrodes are immersed and separated by a distance such that current flows between them through the electrolyte. They are then linked to the power source, completing the electrical circuit. The reaction is driven by a direct current from the power source, which attracts ions in the electrolyte to the oppositely charged electrode.

Metal, graphite, and semiconductor material electrodes are commonly utilised. The chemical reactivity of the electrode with the electrolyte, as well as the production cost, influence the electrode selection. Graphite (named plumbago in Faraday’s time) or platinum were traditionally used as non-reactive anodes for electrolysis. They were discovered to be among the least reactive anode materials. Platinum erodes slowly compared to other materials, while graphite crumbles and can form carbon dioxide in aqueous situations but does not participate in the reaction otherwise. Because anode wear is increased owing to oxidation at the anode, cathodes might be manufactured of the same material or a more reactive one.

Electrolysis: 

Electrolysis is a method of producing electricity. Electrolysis is characterised by the exchange of atoms and ions caused by the removal or addition of electrons caused by the applied current. Electrolysis’ intended products are frequently in a different physical state than the electrolyte and can be removed via physical procedures (e.g. by accumulating gas above an electrode or precipitating a substance from the electrolyte). The quantity of products produced is proportional to the current, and the products produced in two or more electrolytic cells linked in series to the same power source are proportional to their equivalent weight. They’re known as Faraday’s laws of electrolysis.

Each electrode attracts ions with the opposing charge. The electron-providing (negative) cathode attracts positively charged ions (cations). The electron-extracting (positive) anode attracts negatively charged ions (anions). In this process, electrons are injected as a reactant at the cathode and removed as a product at the anode. Oxidation is the loss of electrons in chemistry, whereas reduction is the gain of electrons.

When neutral atoms or molecules, such as those on an electrode’s surface, get or lose electrons, they become ions, which can dissolve in the electrolyte and react with other ions.

Compounds form when ions lose or gain electrons and become neutral, separating them from the electrolyte.Cu2+ and other positive metal ions form a coating on the cathode. Electroplating, electrowinning, and electrorefining are all terminologies used to describe this process.

When an ion gains or loses electrons without becoming neutral, its electrical charge changes.

Example :

When brine is electrolyzed, for example, hydrogen and chlorine gases bubble up from the electrolyte and are collected. The immediate reaction is as follows:

2 NaCl + 2 H2O → 2 NaOH + H2 + Cl2

The anode reaction produces chlorine gas from chlorine ions:

2 Cl− → Cl2 + 2 e−

At the cathode, the process produces hydrogen gas and hydroxide ions:

2 H2O + 2 e− → H2 + 2OH−

The OH ions created at the cathode are free to diffuse throughout the electrolyte to the anode since there is no partition between the electrodes. Less Cl2 escapes from the solution as the electrolyte becomes more basic due to the creation of OH, as it begins to react with the hydroxide at the anode, creating hypochlorite:

Cl2 + 2NaOH → NaCl + NaClO + H2O

The more Cl2 has an opportunity to interact with NaOH in the solution, the less Cl2 emerges at the solution’s surface and the faster hypochlorite formation develops. The temperature of the solution, the amount of time the Cl2 molecule is in contact with the solution, and the concentration of NaOH all play a role.

Energy Change : During electrolysis, energy is changed.

The quantity of electrical energy that must be provided equals the reaction’s change in Gibbs free energy plus the system’s losses, which can (in theory) be arbitrarily near to zero, therefore the maximum thermodynamic efficiency equals the enthalpy change divided by the reaction’s free energy change. Some energy is wasted as heat because the electric input is usually greater than the enthalpy change of the process. In some cases, such as when steam is electrolyzed at high temperatures to form hydrogen and oxygen, the opposite is true, and heat energy is absorbed.This heat is absorbed from the environment, and the heating value of the hydrogen created exceeds the electric input.

Conclusion: 

Electrolysis is very significant in today’s world. Electrolysis is crucial in most people’s daily lives, whether it’s for the manufacturing of aluminium, electroplating metals, or the synthesis of specific chemical compounds.