Proton Exchange Membrane Fuel Cells (PEMFC) are promising contender as the next generation energy source because of their striking features including high energy density, low operating temperature, easy scale up and zero environmental pollution.

1. Report on
PROTON EXCHANGE
MEMBRANE FUEL CELL
Submitted To: Professor Yang So-Young
Submitted By: Subir Paul
Student ID: 2018227073
Semester: 20182
Submission Date: 4th December, 2018

2. Fuel Cells
2
A fuel cell can be defined as a galvanic cell that converts the chemical energy straight into electrical
energy. This energy conversion device generates DC (Direct current) electricity from electro-chemical
reaction of various chemical fuels. This electrochemical device does not burn fuels, but fuses them
with oxygen to produce water. This one step electro-chemical reaction is obstructed by an electrolyte,
which puts apart the two reactants. Consequently, two half reactions take place at the electrode
Anode Reaction: 2H2 + 2O2
−
→ 2H2O + 4e−
Cathode Reaction: O2 + 4e−
→ 2O2
−
Overall Cell Reaction: 2H2 + O2 → 2H2O
The ions only transfer through the electrolyte to the other electrolyte. The fuel cell is a sample robust
system that contains only four active elements: cathode, anode, electrolyte and interconnect. Fuel
cells show following eight significant advantage over combustion-based heat engines or conventional
electricity generations:
1.Single step (form chemical to electrical energy)process.
2.No to negligible (if fossil fuels are used) air pollution and useful byproduct e.g. water.
3.Higher efficiency than diesel or gas engines (Theoretically 100% efficiency but practically 80%
efficiency can be achieved in high temperature turbine hybrid systems that can exploit the generated
heat).
4.Consistent efficiency at small load.
5.Reduced weight, particularly in mobile applications.
6.Low maintenance cost owing to no moving parts.
7.No sound pollution compared to internal combustion engines .
8.Quit compatible with contemporary energy carriers such as hydrogen and sources of renewable
energy.

3. 3
Though the very first crude fuel cell was developed by William Grove exactly 179 years ago from now,
because of the technical difficulties and lack of appropriate materials there are still not deemed as
commercially feasible product.
Classification of Fuel Cells

4. 4
Proton Exchange Membrane Fuel Cells
Proton Exchange Membrane Fuel Cells (PEMFC) are promising contender as the next generation
energy source because of their striking features including high energy density, low operating
temperature, easy scale up and zero environmental pollution. The key component of PEMFCs is the
polymeric proton exchange membrane (PEM) which serves as a solid electrolyte. In presence of
water, the PEM swells and its acidic functional groups dissociate to form protons free to move
throughout the membrane; thus the conductivity of PEM comes about. PEMFCs also use platinum-
based materials as catalyst. In early 1960s, the initial version of a PEMFC was build for the Gemini
spacecraft. Owing to short lifetime of the membrane and high cost, in that time its uses excluded in
fields other than space flight. Following a dormant phase lasting nearly three decades, some
remarkable progress in PEMFC properties were acquired due to an amalgamation of two major
aspects:
I.Innovation of Nafion as PEM and
II.Introduction of a new catalyst-ink techniques for electrode fabrication, which simultaneously
increased the efficiency and reduced the amount of platinum catalyst.
Working Principal of PEMFC

5. Efficiency of PEMFC
The PEMFC efficiency can be defined as the ratio between cell output voltage and theoretical cell
potential. The electrical work, Wel , generated in a fuel cell is limited by Gives free energy, ΔG, i.e,.
Wel = -ΔG
Theoretical potential of fuel cell, E = ΔG/nF
Where, n = electrons involved in cathode reaction, F = Faraday’s constant.
At 25 C , E =⁰ ΔG/nF = 237,340 J mol-1 / (2 X 96,485 As mol -1) = 1.23 Volt.
So, efficiency of PEMFC = actual cell potentials/1.23 Volts X 100%
Real time potential are thus always smaller compared to the theoretical cell potentials because of the
irreversible voltage losses. These losses are mainly attributable to three factors such as
I.Activation losses (losses owing to sluggish electrode kinetics)
II.Ohmic losses (losses caused by resistance to ion and electron flow through membrane electrode
assembly (MEA) and stack's electrically conductive components, respectively)
III.Concentration losses (losses because of mass transport i.e., when a reactant (i.e., hydrogen or
oxygen) is more quickly used up than supplied).
Components of PEMFC and Their Functions
In a single cell of PEMFC, major hardware components are Membrane Electrode Assembly (MEA),
gaskets and bipolar plates. As single MEA, power house of PEMFC, generates only <1 volt under
ordinary operating conditions, hence multiple MEAs are stacked in series to generate a practical
voltage output. Each Cell in a stack is sandwiched amid two bipolar plates to isolate it from adjacent
cells. Bipolar plates are typically built with metal, carbon (graphite) or composites.

6. It possesses grooved channels, called ''flow field'', in their structure, which allow gases to flow over the
MEA. Inside all bipolar plates, additional channels are present for liquid coolant circulation. Around the
edges of the MBA, gaskets made of a rubbery polymer are added to prevent gas leakage. Table 2
discusses about the functions of components of PEMFC.
Components Functions
PEM (Electrolyte)
Allows protons transfer from anode to cathode. Separates two half reactions
i.e., oxidation and reduction.
Electrocatalyst (Electrode)
Lowers the activation energy and thus facilitates the reaction of oxygen and hydrogen
i.e., increases the reaction rate or lowers the operating temperature.
Gas Diffusion Layer
(GDL)
Permits uniform diffusion of reactants toward catalyst layer. Allows electron
conduction from anode to cathode.
Let out the water and heat produced by electrochemical reaction at the cathode.
Supports MEA structure.
Bipolar plate
Guides reactant gases through flow channels toward respective electrodes. Leads the
way 0ut for generated heat and water. Partitions reactant gases in adjacent cells.
Acts as inner structural support for PEMFC stack.
Current collector Passes collected current in/out of external circuit.
End plates
Gives enough contact pressure in PEMFC stack with the intention of preventing
reactants from leaking and reducing contact resistance between layers.
Gaskets
Seal the fluid escapes to keep them in their respective zones in PEMFC.
Heating/Cooling Plates Controls the optimum temperature for operation of PEMFC
Reactant gases manifold Delivers reactants to each cell.

7. Proton Exchange Membrane
A PEM isolates the anode and cathode to avoid direct contact between oxidation and fuel. But its main
purpose is to conduct protons only and block the electrons. It incorporates numerous proton conductive
functional groups that allow protons to move from one group to another. A good PEM should at least
have following seven criteria:
a.High proton conductivity,
b.Sufficient mechanical strength,
c.Chemical, electrochemical and thermal stability under operating conditions
d.Very little hydrogen and oxygen by-pass
e.Low cost
f.Thin-film formability, and
g.Overall compatibility with other cell components.
Nafion® Membrane
Nafion®, in fact, is the most operated and designated PEM for PEMFCs and DMFCs. Between 1960
and 1980, the U.S. chemical company Du Pont de Numerous began delivery of ion-exchange
membranes of a new type trade-named Nafion®. Nafion® not only exhibited a twofold increment in
specific conductivity of the membrane but also extended the life time by four orders of magnitude (104 to
105 h). Nafion® is a synthetic polymer incorporating perflurovinyl ether groups terminated with sulfonate
group. In contact of water, Nafion® segregates into hydrophilic domains and hydrophobic fluorocarbon
domains.
Based on the thickness of the commercial Nafion® membrane, DuPont have launched several types of
Nafion® membranes such as Nafion® 105, 112, 1135, 115, 117 and 1110. Among these, Nafion® 117
is mainly used for its easy modification.

8. Proton Conducting Mechanism
Proton conduction mechanism in Nafion® membrane can be divided into two sections: Proton
conduction in surface and bulk.
Surface transport mechanism can be explained by two mechanism: Grotthuss and Vehicle
mechanism. The variation of relative humidity (RH) in membrane decides the proportion of proton
conductivity on the basis of the Grotthuss and vehicle mechanisms. In vehicle mechanism, proton
propagates together with H20 molecules by complex formation (for example H3O+ form) and for this
required number of water molecules are small. On the contrary, in Grotthuss mechanism, proton
transfers by proton hopping from one proton carrier site to an adjacent one through hydrogen bonds.

9. Water Content of Nation® Membrane
The pores of Nation® can hold water in considerable amount. The water content λ of Nation® is a very
significant value and can be determined by experimental data using following equation:
λ = (water molecules) absorbed / (Sulfonic acid groups) total
MOF Crystals as Filler Materials of PEMs
Metal-organic frameworks (M0Fs) are one of the most attractive and a fairly new group of porous, highly
crystalline, coordination polymers which contain metal centers joined with organic linker by coordination
bonds. Among their lots of diverse applications, MOFs act as promising candidates for electrolyte
materials of fuel cells because of their controllable structure, large surface area and desirable
electrochemical properties. Usually, the inorganic nodes in the structure contain ions of metal such as
Al3+
, Co2+
, Cr3+
, Cu+
, Cu2+
, Fe3+
, Mn2+
, Zn2+
and Zr4+
or secondary building units (SBUs) consist of nearly
all transition metals, Group-I and Group-IIA metals, lanthanides and actinides. The general organic
linkers include negative functional groups like carboxylate, pyridyl, phosphonate, imidazolate or other
azolate in their bi-, tri- or tetratopic forms.

10. Electrocatalysts
An electrocatalyst is a chemical substance that increase the rate of an electrochemical reaction
without being consumed in the process; after the reaction, it can potentially be recovered from
the reaction mixture and is chemically unchanged. The electrocatalyst lowers the activation
energy required, allowing the reaction to proceed more quickly or at a lower temperature. In a
fuel cell, the electrocatalyst facilitates the reaction of oxygen and hydrogen. It is usually made of
platinum powder very thinly coated onto carbon paper or cloth. Instead of Pt, Pt-alloys can be
used as electrocatalyst. An electrocatalyst is rough and porous so the maximum surface area of
the platinum can be exposed to the hydrogen or oxygen. The platinum-coated side of the catalyst
faces the membrane in the fuel cell.
Chemical and Physical Characterization
Structural Study
XRD Analysis
Surface Morphology
BET Analysis
Thermal Stability
Mechanical Stability
Oxidative Stability
Water Uptake
Ion Exchange Capacity
Proton Conductivity
Performance Test in Single Cell