The document discusses different types of fuel cells including hydrogen fuel cells, microbial fuel cells (MFCs), and polymer electrolyte membrane (PEM) fuel cells. It provides details on their working principles, components, and reactions. Hydrogen fuel cells combine hydrogen and oxygen to produce electricity, heat, and water. MFCs use microorganisms and organic substrates to generate electricity. PEM fuel cells are currently leading technology for vehicles and applications, using a proton-conducting polymer membrane and platinum catalysts.

1. AYESHA 19-EE-02
SADAKAT 19-EE-03
HALEEMULLAH 19-EE-04
SUFFIYAN 19-EE-05
BABAR X-EE-21
GROUP MEMBERS

2. FUEL CELL
A fuel cell is an electrochemical cell that converts the chemical
energy of a fuel and an oxidizing agent into electricity through a
pair of redox reactions.

3. WORKING OF FUEL
CELL:-
A fuel cell is a device that generates electricity by
a chemical reaction. Every fuel cell has two
electrodes called, respectively, the anode and
cathode. The reactions that produce electricity
take place at the electrod

4. HYDROGEN FUEL CELL:-
Hydrogen Fuel Cells. A fuel cell combines hydrogen and
oxygen to produce electricity, heat, and water. Fuel cells are
often compared to batteries. Both convert the energy
produced by a chemical reaction into usable electric power.

5. WORKING OF
HYDROGEN FUEL CELL
A fuel cell needs three main components to create
the chemical reaction: an anode, cathode and an
electrolyte. First, a hydrogen fuel is channeled to
the anode via flow fields. Hydrogen atoms become
ionized (stripped of electrons), and now carry only
a positive charge. Then, oxygen enters the fuel cell
at the cathode, where it combines with electrons
returning from the electrical circuit and the ionized
hydrogen atoms. Next, after the oxygen atom picks
up the electrons, it then travels through the
electrolyte to combine with the hydrogen ion. The
combination of oxygen and ionized hydrogen serve
as the basis for the chemical reaction.

6.  What are Microbial Fuel Cells.
 Working principle of MFCs And schematic diagram.
 Types of Microbial Fuel Cells.
 Applications of Microbial Fuel Cells.

7. MFCs are used in water treatment to harvest energy utilizing anaerobic digestion. The process can also red
uce pathogens. However, it requires temperatures upwards of 30 degrees C and requires an extra step in o
rder to convert biogas to electricity. Spiral spacers may be used to increase electricity generation by creati
ng a helical flow in the MFC. Scaling MFCs is a challenge because of the power output challenges of a larg
er surface area.
“MFCs are electrochemical devices in which electr
oactive becteria are used to produce electricity thr
ough the process of substrate oxidation in a cell.”
Basic Deffinati
on :-

8. Construction of the cell;
 A typical MFC consists of anode and cathode compartments,
 That are separated by a cationic membrane.
 The Microbes to be used reside in the anode compartment , Whi
ch facilitates Anaerobic conditions.
 External circuit to connect the two compartments
 Mediator to be added if desired.
 catalyst for faster oxygen reduction.
 The micro Organisms commonly used are “Shewanella Putrefacien
s” and “Aeromonas Hydrophila” etc.

9. Working of the Cell;
 The reaction starts at the Anode where these Microbes reside , they metabolize organic compo
unds such as glucose which act as electron donor. The metabolism of these organic compounds
generates electrons and protons.
when oxygen is not present, these microbes produce carbon dioxide, hydrons (hydrogen ions),
and electrons,
 These Electrons are then transferred to the anode surface. From anode, the electrons move to
cathode through the the external electrical circuit,
 while the protons migrate through the electrolyte and then through the cationic membrane.
 Electrons and protons are consumed in the cathode compartment by reduction of soluble elec
tron acceptor, such as oxygen or hexacynoferrate.
 Electrical power is harnessed by placing a load between the two electrode compartments
 To accelerate the oxygen reduction on the surface of the cathode, platinum is commonly used
because of its excellent catalytic ability. However, the high cost of platinum is a major limitation t
o MFC application and economic viability.
C12H22O11 + 13H2O → 12CO2 + 48H+
+ 48e−

10. Flow Chart,

11. Scematic Diagram of Standard MFCs

12. There are several types of Microbial fuel cells based on different factors that may effect them
1. Mediated
Most microbial cells are electrochemically inactive. Electron transfer from microbial cells to the ele
ctrode is facilitated by mediators such as methyl blue, humic acid, and neutral red. However Mo
st available mediators are expensive and toxic.
2. Mediator-free
Mediator-free microbial fuel cells use electrochemically active bacteria to transfer electrons to the
electrode (electrons are carried directly from the bacterial respiratory enzyme to the electrode). A
mong the electrochemically active bacteria are Shewanella putrefaciens Aeromonas hydrophila a
nd others.
3. Soil-based
Soil-based microbial fuel cells adhere to the basic MFC principles, whereby soil acts as the nutrien
t-rich anodic media, the inoculum and the proton exchange membrane (PEM). The anode is plac
ed at a particular depth within the soil, while the cathode rests on top the soil and is exposed to a
ir.

13. 4.Phototrophic biofilm
Phototrophic biofilm MFCs use a phototrophic biofilm anode containing photosynthetic microo
rganism such as chlorophyta and candyanophyta. They carry out photosynthesis and thus
produce organic metabolites and donate electrons.
5. Ceramic membrane
PEM membranes can be replaced with ceramic materials. Ceramic membrane costs can be s
uper low. The macro porous structure of ceramic membranes allows good transport of ions.

14.  Power generation
MFCs are attractive for power generation applications that require only low power, but wh
ere replacing batteries may be impractical,
 Education
Soil-based microbial fuel cells serve as educational tools, as they encompass multiple scient
ific disciplines (microbiology, geochemistry, electrical engineering, etc.) and can be made us
ing commonly available materials
 Biosensor
An MFC-type BOD sensor can provide real-time BOD values in waste water .
 Wastewater treatment
MFCs are used in water treatment to harvest energy utilizing anaerobic digestion. The proc
ess can also reduce pathogens.

15.  What are Polymer electrolyte membrane fuel cell
 Their Working Principle and Scematic Diagram.
 types of Polymer electrolyte membrane fuel cells

16. “Polymer electrolyte membrane (PEM) fuel cells, ar
e fuel cells that convert the chemical energy stored
in hydrogen fuel directly and efficiently to electrical
energy with water as the only byproduct”
These have the potential to reduce our energy use,
pollutant emissions, and dependence on fossil fuel
s significantly .
PEMFC cells are currently the leading technology f
or light duty vehicles and materials handling vehicl
es, and to a lesser extent for stationary and other a
pplications.

17. Polymer electrolyte membrane;
A proton-exchange membrane, or polymer-electrolyte membrane (PEM), is a semiper
meable membrane generally made from ionomers and designed to conduct protons
while acting as an electronic insulator and reactant barrier, e.g. to oxygen and hydroge
n gas.
PEM fuel cells use a solid polymer membrane (a thin plastic film) as the electrolyte. This polymer is permeable to pro
tons when it is saturated with water, but it does not conduct electrons.
An ionomer is a polymer composed of repeat units of both electrically neutral repeating units and ionized uni
ts covalently bonded to the polymer backbone as pendant group moieties.

18. BASIC PRINCIPLE OF PEMFCS
 The working principle of PEFCs is based on the anode-oxidation of hydrogen (fuel) to protons:
 and the reduction of oxygen to water at the cathode terminal :
 Based on the thermodynamic data of the reactions,
the theoretical cell voltage is calculated via:  With the Gibbs free energy of the
electrochemical
reactions “ΔG”
=> the number of the electrons “n”
and
=>the Faraday constant “F”

19.  At 25°C, the theoretical hydrogen/oxygen fuel cell voltage is 1.23V.
 In order to accurately predict the voltage, the performance, and the efficiency of the PEFC, numerous physi
cal and chemical phenomena should be taken into account. For this purpose, it is necessary to investigate t
he processes that contribute to the voltage losses and determine their contribution [1]. The cell voltage of t
he PEFC is expressed by:
“Ucell” — cell voltage
; “Uoc”—open-circuit voltage;
“ηc, ηa” —voltage losses at the cathode and anode
“ηmem” —membrane overvoltage,
“ηGDL and ηBP” —ohmic voltage drops at the gas diffusion layer (GDL) and bipolar plate (BP).
Where;

21. WORKING PRINCIPLE OF PEMFC
 Polymer electrolyte membrane (PEM) fuel cells employ a polymer membrane with acid side grou
ps to conduct protons from the anode to cathode.
 Water management in the fuel cell is critical for PEM fuel cell operation.
Sufficient water must be absorbed into the membrane to ionize the acid groups;
excess water can flood the cathode of the fuel cell diminishing fuel cell performance limiting the
power output.
 Hydrogen-oxygen PEM fuel cell. Hydrogen molecules dissociatively adsorb at the anode and are
oxidized to protons.
 Electrons travel through an external load resistance.
 Protons diffuse through the PEM under an electrochemical gradient to the cathode.
 Oxygen molecules adsorb at the cathode, are reduced and react with the protons to produce wa
ter.

22.  The product water is absorbed into the PEM, or evaporates into the gas streams at the anode and c
athode.
 Proton conductivity in Nafion, and most other polymer electrolytes, increases with water activity, an
d is maximized when equilibrated with liquid water (water activity aw=1).
 Operation at aw=1 minimizes the membrane resistance for proton conduction, but results in water
condensation which inhibits mass transfer to the electrodes

23.  A proton exchange membrane fuel cell transforms the chemical energy liberated during the electrochemica
l reaction of hydrogen and oxygen to electrical energy, as opposed to the direct combustion of hydrogen a
nd oxygen gases to produce thermal energy.
 A stream of hydrogen is delivered to the anode side of the MEA. At the anode side it is catalytically split int
o protons and electrons. This oxidation half-cell reaction or hydrogen oxidation reaction (HOR) is represent
ed by:
 At the anode:

24.  The newly formed protons permeate through the polymer electrolyte membrane to the cathode
side. The electrons travel along an external load circuit to the cathode side of the MEA, thus cre
ating the current output of the fuel cell. Meanwhile, a stream of oxygen is delivered to the catho
de side of the MEA. At the cathode side oxygen molecules react with the protons permeating th
rough the polymer electrolyte membrane and the electrons arriving through the external circuit
to form water molecules. This reduction half-cell reaction or oxygen reduction reaction (ORR) is
represented by:
 At the cathode:

25.  Overall reaction:
 The reversible reaction is expressed in the equation and shows the reincorporation of the hydrogen p
rotons and electrons together with the oxygen molecule and the formation of one water molecule. T
he potentials in each case are given with respect to the standard hydrogen electrode.