This document discusses the application of carbon nanotubes in fuel cells to improve performance and lower costs. It first provides background on fuel cells and their advantages over conventional power generation methods. It then discusses how polymer electrolyte fuel cells (PEFCs) like proton exchange membrane fuel cells (PEMFCs) and direct methanol fuel cells (DMFCs) have attracted attention but are limited by high costs. Carbon nanotubes can be incorporated into fuel cell components to address these limitations. Specifically, carbon nanotubes added to proton exchange membranes can increase strength and durability while maintaining proton conductivity. Carbon nanotubes are also effective catalyst supports and can reinforce bipolar plates, improving electrical conductivity.

1. APPLICATION OF CARBON
NANOTUBES IN FUEL
CELLS
Aditya Bhardwaj

2. Fuel cells are electrochemical devices that convert chemical energy in fuels into
electrical energy directly, promising power generation with high efficiency and low
environmental impact. Because the intermediate steps of producing heat and
mechanical work typical of most conventional power generation methods are
avoided, fuel cells are not limited by thermodynamic limitations of heat engines
such as the Carnot efficiency. In addition, because combustion is avoided, fuel cells
produce power with minimal pollutant. However, unlike batteries the reductant and
oxidant in fuel cells must be continuously replenished to allow continuous operation
Most interesting today are those fuel cells that use common fuels (or their derivatives)
or hydrogen as a reductant, and ambient air as the oxidant.
Fuel cells

3. Basic Structure
A typical fuel cell [1]

4. • Polymer electrolyte fuel cells(PEFCs), operated at 100 ͦ C have attracted
considerable attention.
• These include Proton Exchange membrane fuel cells (PEMFCs), which use
hydrogen as fuel, Direct methanol fuel cells (DMFCs), which use liquid methanol
as fuel.
• High cost (110 $ per kW) due to high loading of the noble metal catalysts on
the electrodes and the use of perfluorosulfonic acid membrane and durability
hamper the use of PEFCs.
• Carbon nanotubes (CNTs) can be incorporated into components of fuel cells to
improve performance and lower their cost.
• Due to high mechanical strength and toughness to weight resistance, CNTs are
used as fillers to improve strength of Proton exchange membrane (PEM).
• High surface area and electrical conductivity make them a suitable material for
electrocatalyst supports.
Polymer electrolyte fuel cells and CNTs

5. Schematic of
membrane electrode
assembly
(Iyuke et.al 2003 )[3]
The Membrane electrode assembly (MEA) consists of a sheet of proton conducting
polymer electrolyte membrane with two Pt/C electrodes, which are the anode and
cathode bonded to the opposite sides of the membrane sheet. The arrangement is then
compressed on both sides by grooved bipolar plates or grooved end plates in the case
of single cell, to transport the H2 and O2/air respectively to the electrodes.
Membrane electrode assembly

6. Proton exchange membrane (PEM)
• An ideal PEM must be:
1. Proton conductive (proton transfer from anode to cathode)
2. Electrically insulating
3. Low permeability to feeding fuels
4. High chemical stability
5. Mechanically strong
Nafion membrane commonly used
due to high proton conductivity
and good thermal and mechanical
stability.

7. CNTs in PEM
• High young modulus (1000 GPa), High tensile strength (63 GPa) and
lightness make CNTs to be used as fillers.
• Nafion membrane fail at sufficiently high temperature, swelling and
contraction of Nafion membrane change dimension of membrane, which
affects fuel cells performance and work life.
• Liu et al. reported that the incorporation of 1wt.% CNTs into Nafion could
decrease the dimensional change of membrane, whilst maintain the
proton conductivity. A sandwich structured electrolyte membrane with a
platinum (Pt)/CNT/Nafion layer interpolated between two plain Nafion
layers was fabricated.
• Thomassion et al. also demonstrated that the incorporation of 2 wt.%
carboxyl acid group decorated multi-walled carbon nanotubes
(MWCNTs) into Nafion could increase Young’s modulus by 160%.
• By blending 3 wt.% H2O2/NaOH oxidized MWCNTs into Nafion
membrane, the tensile strength increased from18.5MPa to 28.6MPa and
the elongation at break increased from112%to 142%.
• MWCNTs were functionalized with polysiloxane, which were then
blended with Nafion to form a proton conducting membrane,these were
stable for 130 ͦ C, proton conductivity improved substantially.

8. Mechanical and electrical reinforcement of bipolar plates with CNTs
Table: Tensile strength, electrical conductivity and resistivity of polymer and
CNT-polymer blends (Wu and Shaw 2004b) for PEM fuel cell bipolar plates. [3]

9. CNT as catalyst support
SWCNT based PEM assembly for H2 /O2
fuel cells [5]
Ultra low loading Pt nanoparticles with
MWCNTs in hydrogen PEMFC[6]
Power density – 28-30 mW/cm2 Power density – 613 mW/cm2

10. Pt- Ru/CNTs film based MEA for DMFC [7]

11. References
1. Hornyak, Gabor L., et al. Fundamentals of nanotechnology. CRC press, 2008.
2. Zhang, Wei, S. Ravi, and P. Silva. "Application of carbon nanotubes in polymer
electrolyte based fuel cells." Reviews on Advanced Materials Science 29.1 (2011):
1-14.
3. Mahalik, Nitaigour Premchand. Micromanufacturing and nanotechnology. Berlin
[etc.]: Springer, 2006.
4. Akbari, Elnaz, and Zolkafle Buntat. "Benefits of using carbon nanotubes in fuel
cells: a review." International Journal of Energy Research 41.1 (2017): 92-102.
5. Girishkumar, G., et al. "Single-wall carbon nanotube-based proton exchange
membrane assembly for hydrogen fuel cells." Langmuir 21.18 (2005): 8487-8494.
6. Tang, Jason M., et al. "High performance hydrogen fuel cells with ultralow Pt
loading carbon nanotube thin film catalysts." The Journal of Physical Chemistry
C 111.48 (2007): 17901-17904.
7. Li, Wenzhen, et al. "Pt− Ru supported on double-walled carbon nanotubes as high-
performance anode catalysts for direct methanol fuel cells." The Journal of Physical
Chemistry B 110.31 (2006): 15353-15358.