Conductors and Non-Conductors Substances can be classified as conductors and non-conductors based on their ability to conduct electricity. Conductors: Substances that allow electric current to flow through them are called conductors. For example, Plastic, Wood, etc. Non-Conductors: Non-conductors are insulators that do not allow electricity to pass through them. For example, Copper, Iron, etc. Types of Conductors Conductors are divided into two groups: Metallic conductors and Electrolytes. Metallic Conductors: These conductors conduct electricity by the movement of electrons without any chemical change during the process. This type of conduction happens in solids and in the molten state. Electrolytes: They conduct electricity by the movement of the ions in the solutions. It is present in the aqueous solution. Distinguish between Metallic and Electrolytic Conduction Metallic Conduction Electrolytic Conduction The movement of electrons causes the electric current The movement of ions causes the electric current There is no chemical reaction Ions get ionised or reduced at the electrodes There is no transfer of matter It involves the transfer of matter in the form of ions Follows Ohm’s law Follows Ohm’s law Resistance increases with an increase in temperature Resistance decreases with an increase in temperature Faraday’s law is not followed Follows Faraday’s law Electrolytes (a) Substances whose aqueous solutions allow the conductance of electric current and are chemically decomposed are called electrolytes. (b) The positively charged ions furnished by the electrolyte are called cations, while the negatively charged ions furnished by the electrolyte are called anions. Types of Electrolytes (a) Weak electrolytes: Electrolytes that are decomposable to a very small extent in their dilute solutions are called weak electrolytes. For example, organic acids, inorganic acids and bases etc. (b) Strong electrolytes: Electrolytes that are highly decomposable in aqueous solution and conduct electricity frequently are called electrolytes. For example, mineral acid and salts of strong acid. Electrode For the electric current to pass through an electrolytic conductor, the two rods or plates called electrodes are always needed. These plates are connected to the terminals of the battery to form a cell. The electrode through which the electric current flows into the electrolytic solution is called the anode, also called the positive electrode, and anions are oxidised here. An electrode through which the electric current flows out of the electrolytic solution is called the cathode, also called the negative electrode, and cations are reduced there. Electrolysis Electrolysis is the process of chemical deposition of the electrolyte by passing an electric current. Electrolysis takes place in an electrolytic cell. This cell will convert the electrical energy to chemical energy.

1. ELECTOCHEMISTRY

2. What is
electrochemistry?
 Electrochemistry is the study of
chemical reactions which take placeat
the interface of an electrode usually a
solid, metal or semiconductor and an
ionic conductor , theelectrolyte.
 Electrochemistry deals with the
interaction between electricalenergy
and chemical change.

3. History of electrochemistry
t
 English chemist john Daniel and physicist
Michael faraday both credited as founders
of electrochemistrytoday.
 The first germen physicist Otto von
Guericke created the electric
generater,which produced staticelectricity
by applying friction in themachine.
 The English scientist William Gilbertspen
17 years experimenting with magnetism
and toa lesserextentelectricity.
john
Daniel
Michael
faraday

4.  The french chemistcharles francoisde cisternrydu fay
had discovered two types of staticelectricity.
 William Nicholson and Johann Wilhelm Ritter
succeeded in decomposing water into hydrogenand
oxygen byelectrolysis.
 Ritter discovered the process ofelectroplating.
 William Hyde Wollaston made improvements tothe
galvaniccells.
 Orsted’sdiscoveryof the magneticeffectof electrical
currents and further work on electromagnetism to
others.

5.  Michael Faraday'sexperiments led him tostate his two
laws of electrochemistry and john Daniel invented
primary cells.
 Paul Heroult and Charles M.Hall developedan
efficient method to obtain aluminum using
electrolysis of moltenalumina.
 Nernstdeveloped the theoryof theelectromotive force
and his equation known as Nernst equation, which
related thevoltagesof a cell to its properties.
 Quantumelectrochemistrywasdeveloped by Revaz
dogonadeze and hispupils.

6. Oxidation-Reduction
 The term redox stands forreduction-oxidation
 It refers to electrochemical processesinvolving
electron transfer to or from a molecule or iron
changing its states.
 Theatom or moleculewhich loseselectrons is known
as the reducingagent.
 The substancewhich accepts theelectrons iscalled the
oxidizing agent.

7. Balancing redox reactions
 Acidic medium
 Example of manganese reacts withsodium bismuthate
 Unbalanced reaction:
Mn2+ 3+ –
(aq) + NaBiO3(s) → Bi (aq) + MnO4 (aq)
 Oxidation:
4 H2O(l) + Mn2+ → MnO – + 8 H+ + 5 e–
(aq) 4 (aq) (aq)
 Reduction:
2 e– +6 H+ + BiO – → Bi3+ + 3 H O
(aq) 3 (s) (aq) 2 (l)
8 H2O(l) + 2 Mn2+ → 2 MnO – + 16 H+ + 10 e–
(aq) 4 (aq) (aq)
10 e– +30 H+ + 5 BiO – → 5 Bi3+ + 15 H O
(aq) 3 (s) (aq) 2 (l)
 Reaction balanced:
14 H+ + 2 Mn2+
(aq) (aq) + 5 NaBiO3(s) → 7 H2O(l) + 2 MnO4
–
(aq) + 5 Bi3+
(aq) +
5 Na+

8.  Basic medium
 Exampleof reaction between potassium permanganateand
sodium sulfite.
 Unbalanced reaction:
KMnO4 + Na2SO3 + H2O → MnO2 + Na2SO4 + KOH
 Reduction:
3 e– + 2 H2O + MnO4
– → MnO2 + 4OH–
 Oxidation:
2 OH– + SO3
2– → SO4
2– + H2O + 2 e–
 6 e– + 4 H2O + 2 MnO4
– → 2 MnO2 + 8OH–
 6 OH– + 3 SO3
2– → 3 SO4
2– + 3 H2O + 6e–
 Equation balanced:
2 KMnO4 + 3 Na2SO3 + H2O → 2 MnO2 + 3 Na2SO4 + 2 KOH

9.  Neutral medium
 Method to complete combustionof propane.
 Unbalanced reaction:
C3H8 + O2 → CO2 + H2O
 Reduction:
4 H+ + O2 + 4 e– → 2 H2O
 Oxidation:
6 H2O + C3H8 → 3 CO2 + 20 e– + 20H+
 20 H+ + 5 O2 + 20 e– → 10H2O
 6 H2O + C3H8 → 3 CO2 + 20 e– + 20H+
 Equation balanced:
 C3H8 + 5 O2 → 3 CO2 + 4 H2O

10. Standard electrode potential
Toallow prediction of the cellpotential,
tabulationsof standard electrode potential are available.
Tabulations are referenced to the standardhydrogen
electrode.
The standard hydrogen electrode undergoes thereaction
 2 H+
+ 2 e–
→H
(aq) 2

11. Standard electrode potentialsare usually tabulated
as reduction potentials.
The reactionsare reversibleand the roleof particular
electrode in a cell depends on the relative oxi./red.
Potential of both electrodes.
The cell potential is then calculated as the sum of
reduction potential for cathode and the oxidation
potential foranode.
For example, the standard electrode potential for a
copper electrodeis:
Cell diagram
Pt(s) | H2 (1 atm) | H+
(1 M ) || Cu2 +
(1 M ) |
Cu(s)
E°cell = E°red (cathode) – E°red (anode)

12. Gibbs free energy and cell
potential
Though cell potential Cell and get electricity nfaraday
in thecell:
Forstandard cell, thisequationcan wewritten
= -nFEcell
0
= -RTlnK=-nFE0
G cell
Though produce of electric energyconverted into
electricwork,
Wmax=Welectrical= -nFEcell

13. N e r n s t e q u a t i o n
n +
| = E 0 n +
| -
E ( M M ) ( M M ) l n
B u t s o l i d M c o n c e n t r a t e c o n s t a n t
n +
| = E 0 n +
| -
E ( M M ) ( M M ) l n
E x a m p l e o f D a n i e l c e l l
2 +
| = E 0 2 +
| -
E ( C u C u ) ( C u C u ) l n
F o r c a t h o d e :
F o r a n o d e :
2 +
| = E 0 2 +
| -
E ( Z n Z n ) ( Z n Z n ) l n
2 +
| - E 2 +
|
E ( C u C u ) ( Z n Z n )
- E 0 2 +
| - l n
( Z n Z n )
C e l l P o t e n t i a l : E c e l l = :
= E 0 2 +
| - l n
( C u C u )
= E c e l l = E 0
- l n
c e l l

14.  Electrical resistivity
It is an intrinsic property thatquantities how stronglya
given material opposes the flow of electrical current.
Many resistors and conductors have a uniform cross
section with a uniform flowof electriccurrentand made
of one material
The electrical resistivitydefined

15.  Electrical conductivity
The reciprocal of electrical resistivity, and measuresa
material’sability toconductan electriccurrent.
It is commonly represented byσ
Conductivity is definedas
Conductivity SI units of Siemens permeter.

16. Molar conductivity
Molarconductivity is defined as theconductivityof an
electrolyte solution divided by the molar
concentration of the electrolyte, and so measures the
efficiency with which a given electrolyte conducts
electricity insolution.
From definition, the molarconductivity

17. • Twocases should bedistinguished:
Strong eletrolyte and weakelectrolyte
 For strongelectrolyte
Salts, strong acids and strong bases, the molar
conductivitydependsonlyweaklyon concentration.

18.  For weakelectrolyte
The molarconductivitystronglydependson
concentration.
The more dilute a solution, the greater its molar
conductivity, due to increased ionicdissociation.
Forweak electrolyteobeys Oswald'sdilulation law.

19. Kohlrausch’s law of independent
migration of ions
High accuracy in dilutesolutions, molarconductivity
is composed of individual contributions ofions.
Limiting conductivity of anions and cations are
additive, theconductivityof a solutionof a salt is equal
to the sum of conductivity contributions from the
cation and anion
Λ0
m
=v+Λ0
+
+v-Λ0
-

20. Battery
Many types of battery have been commercializedand
represent an important practical application of
electrochemistry.
Early wet cells powered the first telegraph and
telephonesystems, and were the sourceof current for
electroplating.
The zinc-manganese dioxidedry cell was the first
portable, non-spill able battery type thatmade
flashlights and otherportabledevices practical.

21. The mercury battery using zinc and mercuric oxude
provided higher levelsof powerand capacity than the
original dry cell forearlyelectronicdevices.
Lead-acid battery was secondarybattery.
The electrochemical reaction that produced current
was reversible, allowing electrical energy and chemical
energy to be interchanged asneeded.
Lead-acid cellscontinue to be widelyused in
automobiles.

22. The lithium battery, which does not use water in the
electrolyte, provides improved performance overother
types.
Rechargeable lithium ion battery is an essential partof
many mobiledevices.

23. Corrosion
Corrosion is the term applied tosteel rustcaused byan
electrochemical process.
Corrosion of iron in the form of reddish rust, black
tarnish on silver, red orgreen may beappearon copper
and its alloys, such asbrass.

24. Prevention of corrosion
 Coating
Metalscan becoated with paintorother less
conductive metals.
This prevents the metal surface from being exposed to
electrolytes.
Scratchesexposing the metal substratewill result in
corrosion.

25. • Sacrificial anodes
The method commonly used to protect a structural
metal is toattach a metal which is moreanodic than
the metal to beprotected.
This forces the structural metal to be catholic thus
spared corrosion. it is calledsacrificial.
Zinc bars areattached tovarious locationson steel
ship hulls torender the ship hull catholic.
Other metal used magnesium.

26. Electrolysis
The spontaneous redox
reactions of a conventional
battery produce electricity
through the differentchemical
potentials of the cathode and
anode in theelectrolyte.
Electrolysis requires an
external source of electrical
energy to include a chemical
reaction , and this process
takes place in acompartment
called an electrolyticcell.

27. Electrolysis of molten sodium
chlorine
This process can yield large amounts of metallic
sodium and gaseous chlorine, and widelyused on
mineral dressing and metallurgy industries.
When molten, the salt sodium chloride can be
electrolyzed to yield metallic sodium andgaseous
chlorine.
This process takes place in a special cell named
DowR
nea
’sct
cio
en
ls
lt
.hattake place at Down's cell are the following
Anode (oxidation): 2 Cl–
→ Cl2(g) + 2 e–
Cathode (reduction): 2 Na+
+ 2 e–
→ 2 Na
(l) (l)
Overall reaction: 2 Na+
+ 2 Cl–
→ 2 Na + Cl
(l) (l) 2(g)

28. Quantitative electrolysis and
Faraday’s law
Quantitativeaspectsof electrolysiswereoriginally
developed by Michel faraday.
Faraday is alsocredited to havecoined the terms
electrolyte.
Electrolysisamong manyothers whilestudying
analysis of electrochemicalreactions.
Faraday advocateof the lawof conservationof energy.

29. First law
 The mass of products yielded on the electrodes was
proportional to the the value of current supplied to the cell,
the length of time the current existed, and the molar mass
of the substance analyzed.
 The amount of substance deposited on each electrode of an
electrolytic cell is directly proportional to the quantity of
electricity passed through thecell.
m=

30. Second law
Theamountsof bodieswhich areequivalent toeach
other in the ordinary chemical action have equal
quantities of of electricity naturally associated with
them.
Thequantitiesof different elementsdeposited bya
given amount of electricity are in the ratio of the
chemical equivalentweights

31. Applied aspects of
electrochemistry
Industrial electrolyticprocesses
Electrochemical Reactors
Batteries
Fuel cells
Some Electrochemical Devices
Electrochemical Methods of Analysis

32. Branch of electrochemistry
 Photoelectrochemistry
It is subfield of studywithin physical chemistry.
The interest in thisdomain is high in thecontextof
development of renewable energy conversion and
storage technology.
Theeffects of luminousradiation on the propertiesof
electrodes and on electrochemical reactions are the
subject of photoelectrochemistry

33.  Semiconductor’selectrochemistry
Semiconductor material has a band gap and generates a
pair of electron and hole per absorbed photon if the
energy of the photon is higher than the band gap of the
semiconductor.
This property of semiconductor materials has been
successfullyused toconverted solarenergy intoelectrical
energy by photovoltaicdevices.
 Semiconductor-electrolyte interface
When a semiconductorcomes intocontactwith a liquid,
to maintain electrostaticequillibrium
There will be a charge transfer between the
semiconductor and liquid phase,if formal redoxpotential
of redox species lies inside semiconductorband gap.

34. At thermodynamic eqilibrium, the fermi level of
semiconductorand the formal redox potential of redox
species and between interfacesemiconductor.
This introduce n-type semiconductor andp-type
semiconductor.
This semiconductorused as photovoltaicdevicesimilar to
solid state p-n junctiondevices.
Both n and p typesemiconductorcan used as photovoltaic
devices to convert solar energy into electrical energy and
are called photoelectricalcells

35.  Boielectrochemistry
It is branch of electrochemistry and biophysical
chemistryconcerned with topics likecell electron-
proton transport, cell membrane potentials and
electrode reactions of redoenzymes.
Bioelectrochemistry isa science at the many junctions
of sciences.

36. Nanoelectrochemistry
Nanoelectrochemistry is a branch ofelectrochemistry
that investigates the electrical and electrochemical
propertiesof materialsat the nanometersize regime.
Nanoelectrochemistry plays significant role in the
fabricationof varioussensors, and devices fordetecting
molecules atvery law concentrations.

37. The term electrochemical nanostructuring can be used
to mean differentthings.
This term is employed to refer to generation at will of
nanostructure on electrode surface, involving a given
positioning with a certainprecision
The term nanostructure is used to describe the
generation of nanometric patternswith moveor less
narrow size distribution and a periodic or random
ordering on thesurface.
Butwithoutcontrol on the spatial locationof the
nanostructure.

38. Application of electrochemistry
There arevariousextremely importantelectrochemical
processes in both nature andindustry.
The coating of objects with metals or metal oxides
through electrodeposition and thedetectionof alcohol in
drunken drivers through the redox reactionof ethanol.
Diabetes blood sugar meters measure theamountof
glucose in the blood through its redox potential.

39. The generation of chemical energy through
photosynthesis in inherently an electrochemicalprocess.
Productionof metals likealuminiumand titanium from
theirores.
 For Photoelectrochemistry
Artificial photosynthesis
Regenerative cell or Dye-sensitizedcell
Photo electrochemical splitting ofwater

40.  For Boielectrochemistry
Someof different experimental techniques thatcan be
used to study bioelectrochemicalproblems.
Ampermetic of biosensors
Biofuel cells
Bioelectrosynthesis