Development of nafion/ palladium nanofiller as nanocomposite membrane for fuel cell applications
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Authors
Mothibi, Mokone Constance Selina
Issue Date
2024-01
Type
Dissertation
Language
en
Keywords
UCTD
Alternative Title
Abstract
The nanocomposite membranes were fabricated by incorporating palladium
nanoparticles into Nafion® matrix to develop suitable membrane to be used as polymer
electrolyte membrane (PEM) in Direct Methanol Fuel Cell (DMFC). The effect of
palladium loading was studied to explore a suitable membrane for DMFC. The recast
method was used to synthesize the nanocomposites membranes. Commercial
palladium nanoparticles were used as reference for synthesized palladium
nanoparticles and palladium nanocomposite membranes. The synthesized palladium
nanoparticles by sol-gel method were characterized by TEM, UV-vis, FTIR and DLS.
The morphology and crystalline structure of nanocomposite membranes were
characterized by FESEM, XRD, FTIR. The distribution of palladium nanoparticles
within Nafion® membrane was confirmed by EDS. The thermal properties were
analysed by TGA and DSC. The mechanical properties were also investigated.
To evaluate suitability of palladium nanocomposite membranes as polymer electrolyte
membranes (PEMs) in DMFC properties such as water uptake (WU), water contact
angle, methanol permeability, ion exchange capacity (IEC), proton conductivity and
selectivity were determined.
The palladium nanocomposite membranes indicated the lowest water uptake of
0.37% at 25°C and highest water uptake of 14.8% at 100°C. The results of water
uptake indicated hydrophobic behaviour which corresponds to water contact angle.
The highest water contact angle of 100.3° and lowest water contact angle of 84°were
recorded for nanocomposite membrane.
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The mechanical properties of nanocomposite membranes such as tensile strength,
elastic modulus (stiffness) and elongation at break were improved for all
nanocomposite membranes.
The methanol permeability of nanocomposite membranes was improved with reduced
methanol permeability of 3.5 × 10-7 cm-1s-1 for commercial PdNps/Nafion®, 3.6 × 10-7
cm-1s-1 for PdEG22/Nafion®, 3.8 × 10-7 cm-1s-1 for PdEG33/Nafion®, 4.5 × 10-7 cm-1s-1
for PdEG11/Nafion® compared to 9.12 × 10-7 cm-1s-1 of pristine recast Nafion®
membrane at temperature of 80°C. The ion exchange capacity recorded values were
1.28 mm/g for PdEG22/Nafion®, 1.32 mm/g for PdEG33/Nafion®,1.47 mm/g for
PdEG11/Nafion®,2.18 mm/g commercialPdNps/Nafion® compared to 0.81mm/g of
pristine Nafion®. The proton conductivity of 0.6 Scm-1 (PdEG11/Nafion®), 0.41 Scm-1
(PdEG22/Nafion®), 0.28 Scm-1 (PdEG33/Nafion®), 0.26 Scm-1 (commercial
PdNps/Nafion®) was achieved comparable to pristine Nafion® with 0.25 Scm-1.The
membrane selectivity of palladium nanocomposite membranes showed the
membranes are suitable to be used as PEM in DMFC due to their selectivity values
recorded as 1.33 × 106 Sc cm-3 for PdEG11/Nafion®, 1.14 × 106 Sc cm-3 for
PdEG22/Nafion®, 7.4 × 105 Sc cm-3 for both PdEG33/Nafion® and commercial
PdNps/Nafion® compared to pristine Nafion® (2.7 × 105 Sc cm-3) and their ability to
reduce methanol crossover.