Types of Electrochemical Cells

This lecture briefly describes fundamentals of electrochemical cell and illustrate the various types of cells and possible corrosion cites.

1. Types of Electrochemical Cell Presented By : Engr. Mukesh Kumar Lecturer, Dept . Metallurgy and Materials Engineering MUET Jamshoro

2. CONTENTS Reflection of last class Electrochemistry What is electrochemical cell Types of electrochemical cells Activity 2

3. Reflection of Last class Ask a friend sitting next to you: What electrode potential? How can I know that whether the reaction is spontaneous and non-spontaneous. Can you give me few examples of spontaneous and non spontaneous reactions Which metal will corrode if we have Zn/Cu cell. whether Oxidation of metals is corrosion or something else? Dear… for corrosion of metals we must have cell (electrolyte, anode, cathode, metallic path) then why corrosion occurs in single steel bars? 3

4. Electrochemistry It is the study of chemical processes that cause electrons to move . Movements of electrons from one element to another in a reaction known as an oxidation-reduction ("redox") reaction 4 Given the redox reaction  which species is oxidized? Which is reduced? Identify the reducing agent and the oxidizing agent.

5. ELECTROCHEMICAL CELL Electrochemical cell is a device which converts chemical energy into electrical energy or vice versa. Pair of electrodes dipped in electrolyte (solution) constitutes an electrochemical cell, occasionally called a Galvanic cell after L. Galvani (electrochemist, 1737–1798) Such cells capable of generating an electric current from the chemical reactions occurring in them care called Galvanic cells or Voltaic cells. The cells which cause chemical reactions to occur in them when an electric current is passed through them are called electrolytic cells. 5 https://www.sciencedirect.com/topics/chemistry/electrochemical-cell

6. Concentration Cell Temperature Cell Galvanic cell/bimetallic cell/corrosion cell/electrochemical cell Oxygen Differential Cell (Concentration Cell) Electrolytic Cell Single Electrode Cell in Alkaline Solution Single Electrode Cell in Acidic Solution Single Electrode Cell in Aerated Alkaline Solution Types of Electrochemical Cells 6

7. Concentration Cell An electrolytic cell that is comprised of two half-cells with the same electrodes, but differing in concentrations . Working A concentration cell acts to dilute the more concentrated solution and concentrate the more dilute solution, creating a voltage as the cell reaches an equilibrium. This is achieved by transferring the electrons from the cell with the lower concentration to the cell with the higher concentration. 7

8. TEMPERATURE CELL https :// corrosion-doctors.org/Corrosion-Factors-Cells/corrosion-cells-temperature.htm https:// www.tec-eurolab.com/eu-en/differential-temperature-cells.aspx 8 Type of cell which has same metal electrodes immersed in same electrolyte but having different temperature at different points. Both pictures are contradicting. Read following links and give your reason on group.

9. Electrochemical Cell/Bimetallic cell 9 https://www.researchgate.net/publication/270894483_Marine_sediment_microbes_capable_of_electrode _ oxidation_as_a_surrogate_for_lithotrophic_insoluble_substrate_metabolism/ figures?lo =1 What is Bimetallic Cell? Give example and show the direction of electrons

10. Oxygen Differential Cell Similar to concentration cells but amount of dissolved oxygen is different at both electrodes. What will be mechanism for electron transfer from low oxygen level to high level of dissolved oxygen. 10

11. Electrolytic Cell Electrolytic cells convert electrical energy into chemical potential energy. The process is known as electrolysis. The purpose of this is usually to convert reactants into more useful products . Electrolytic cells are one of two major categories of electrochemical cell. 11

12. Oxygen Differential Cell Electrolysis is used to recharge rechargeable batteries: rechargeable batteries operate as voltaic cells when they are powering devices and as electrolytic cells during recharge . For example, the Edison battery is a simple, rechargeable cell invented by Thomas Edison. It consists of two metal electrodes, one made of iron, the other of nickel. During initial charging, a coating of nickel oxide forms on the nickel electrode . The  electrolyte  (the ionic liquid between the electrodes) is aqueous potassium hydroxide. When it is discharging, the Edison cell operates as a voltaic cell. When it is being charged, the cell operates as an electrolytic cell . 12 Discharge , when the cell is delivering electrical energy, the reactions above proceed from left to right . Charging , when the cell is operating electrolytically , converting electrical energy to chemical potential energy, the reactions above proceed from right to left. Ni 2 O 3  + H 2 O + 2 e -  ⇌ 2 NiO + 2 OH - Fe + 2 OH -  ⇌ Fe(OH) 2  + 2 e - https://www.chemicool.com/definition/electrolytic-cell.html

13. Let’s try to understand Single Electrode Cell in Alkaline Solution Single Electrode Cell in Acidic Solution Single Electrode Cell in Aerated Alkaline Solution 13

14. Challenge Game Find a new partner Draw any electrochemical cell Ask your partner about its corrosion mechanism. Note and post all the responses. 14

15. 15 You are welcome to ask any question? ? ?