A Novel Polymer Electrolyte Membrane PES/SPEEK-TiO
2
Potential
for Direct Methanol Fuel Cell
Nyoman Puspa Asri
1a
and Eka Cahya Muliawati
2b
1
Food Technology Progam, Universitas Ciputra, Indonesia
2
Department of Chemical Engineering, Institute of Technology Adhi Tama Surabaya, Indonesia
Keywords: Polymer Electrolyte Membrane (PEM), Direct Methanol Fuel Cell (DMFC), Polyeugenol Sulfonate (PES),
Sulfonated Polyether Ether Ketone (SPEEK), Titanium Dioxide (TiO
2
).
Abstract: A novel polymer electrolyte membrane (PEM) has been developed by combining polyeugenol sulfonate
(PES), which is derived from clove oil, SPEEK, and TiO
2
for direct methanol fuel cell (DMFC), its was
characterized using various analytical techniques, including FTIR and SEM. Additionally, the membrane's
ion proton conductivity (σ) , water(W
upt
) and methanol uptake (M
upt
), Ion exchange capacity(IEC) , and water
contact angle(W
CA
) were tested. The study demonstrated that the PES/SPEEK- TiO
2
membrane, containing 3
wt.% PES, 20 wt.% SPEEK, and 5 wt.% TiO
2
, Showed better results in terms of performance when compared
to the Nafion 117 membrane, particularly in terms of IEC, water uptake, proton conductivity, and methanol
barrier properties. Overall, the study shows the promising potential of the PES/SPEEK- TiO
2
membrane as
an efficient PEM for DMFC applications.
1 INTRODUCTION
Indonesia, as a developing country, is facing a critical
energy crisis due to several factors, including a
persistent increase in household demand, a substantial
population growth rate, and an uneven distribution of
energy sources. Indonesia has long relied on fossil
fuels to generate electrical energy, which has resulted
in an over-reliance on these non-renewable resources.
In recent years, the country has experienced frequent
power outages due to the insufficient energy supply,
particularly in remote areas where the infrastructure
is lacking. As of 2016, the country had an estimated
7.25 billion barrels of fossil fuel reserves,
representing a decline of 0.74% from the previous
year, with natural gas reserves also dropping by
5.04%. Despite the fact that the government has been
transforming 92.1% of the country's complete energy
reserves into petroleum, relying solely on fossil fuels
is not a viable option due to their adverse
environmental impact and limited
availability.(Sihombing, Susilawati, Rahayu, &
Situmeang, 2023). Given the challenges faced by
a
https://orcid.org/0000-0003-2779-6195
b
https://orcid.org/0000-0002-8309-2443
Indonesia in the energy sector, it is imperative to
explore alternative technologies for energy
production. Fuel cells (FCs) offer a promising
solution as they are environmentally friendly and can
contribute towards mitigating global warming and
other climate-related issues.(Braz, Moreira, Oliveira,
& Pinto, 2022; Godula-Jopek & Westenberger,
2022). The Direct Methanol Fuel Cell (DMFC)
is one
type of FC example of an alternative green
technology that can promote environmental
sustainability. DMFC using a liquid methanol
solution as fuel can convert chemical energy into
electrical energy to power various applications, all
while minimizing any negative environmental
impact(Biswas & Wiberforce, 2023).
The DMFC system consists of several essential
components that work together to generate electrical
energy. The fundamental structure of a DMFC system
typically includes a fuel cell stack, which is composed
of individual cells that contain the anode and cathode
electrodes, a PEM positioned between the electrodes.
Bipolar plates are used to separate individual cells
and create electrical connections between them.
Asri, N. and Muliawati, E.
A Novel Polymer Electrolyte Membrane PES/SPEEK-TIO2 Potential for Direct Methanol Fuel Cell.
DOI: 10.5220/0012106100003680
In Proceedings of the 4th International Conference on Advanced Engineering and Technology (ICATECH 2023), pages 173-179
ISBN: 978-989-758-663-7; ISSN: 2975-948X
Copyright
c
 2023 by SCITEPRESS – Science and Technology Publications, Lda. Under CC license (CC BY-NC-ND 4.0)
173

Gaskets, current collectors, and end plates are also
included to complete the assembly and ensure proper
functioning of the system. Overall, the DMFC system
is a complex, yet highly efficient technology that
offers several advantages over traditional energy
sources.(Das, Dutta, Nessim, & Kader, 2020). The
fundamental composition of the DMFC system is
illustrated in Figure 1, where the primary function of
the PEM is to enable the efficient transportation of H
+
ions through the membrane from anode to cathode,
while preventing the passage of electrons, essentially
acting as an insulator (Junoh et al., 2020).
Figure 1: The fundamental composition of DMFC (Junoh,
2020).
The electrons, in order to achieve a stable state,
attempt to recombine on the opposite side of the
membrane and are consequently compelled to travel
through an external electrical circuit to reach the
cathode. Simultaneously, the protons are conveyed
through the electrolyte to the cathode. This process of
exchanging protons and electrons generates electrical
energy. (Walkowiak-Kulikowska, Wolska, &
Koroniak, 2017).
DuPont Company in the mid-1960s developed a
cation-exchange membrane, which is now known as
Nafion®. It comprises a polytetrafluoroethylene
backbone and ionic sulfonate groups that replace the
perfluorinated vinyl ether suspended side chains.
Nafion® possesses exceptional thermal and chemical
durability, along with a high proton-conducting
capability, making it an ideal material for commercial
use (Sazali, Wan Salleh, Jamaludin, & Mhd Razali,
2020). Despite its excellent properties, Nafion® has a
drawback in that its performance diminishes at
temperatures above 80°C. There are several factors
that can be attributed to the decrease in membrane
performance, such as membrane dehydration,
decreased ionic conductivity, weakened air affinity,
diminished mechanical properties, swelling issues,
reduced fuel permeation, and evaporation. Therefore,
several research studies have been conducted to
enhance the membrane's performance for FC
applications.. Moreover, Nafion®'s high cost, which
ranges from US$800 to US$2,000 per square meter,
has impeded the commercialization of PEMs and
DMFC. (Aburabie, Lalia, & Hashaikeh, 2021;
Nicotera, Simari, & Enotiadis, 2020; Shaari et al.,
2018).
Abundant natural resources present a significant
opportunity for the development of alternative and
renewable energy sources, including fuel cells. Clove
oil, which primarily comprises eugenol, is one such
resource that is readily available. Eugenol makes up
70-96% of the oil, highlighting its potential as an
energy source (E. C. Muliawati, Budianto, & Hamid,
2021; E. C. Muliawati et al., 2017). Various polymers
have been synthesized in previous studies using
eugenol as a raw material, and one such example is
Polyeugenol sulfonate (PES) (E. C. Muliawati et al.,
2021, 2017; Ngadiwiyana, Gunawan, Prasetya,
Kusworo, & Susanto, 2022). TiO
2
is an affordable
inorganic material non-flammability and corrosion
resistance with adaptable characteristics that can be
blended into a polymeric matrix to boost thermal
stability and mechanical strength. TiO
2
can be
employed as a co-catalyst in energy applications such
as FC and batteries, or as a doping agent in
PEM.(Abdullah & Kamarudin, 2015; Haragirimana,
Li, Ingabire, Hu, & Chen, 2020; Jiang, 2014; Eka
Cahya Muliawati et al., 2019).
This study involved the incorporation of PES
material into SPEEK to produce several composite
PEM. SPEEK was chosen because it offers various
benefits, such as affordability, excellent chemical
stability, and low methanol permeability.(Fu,
Manthiram, & Guiver, 2007)(Gutru, Peera, Bhat, &
Sahu, 2016; Liu et al., 2014; Salarizadeh et al., 2019;
Yin et al., 2021). The objective of this project is to
develop a polymer electrolyte membrane (PEM)
matrix suitable for DMFC by incorporating TiO
2
as a
filler. TiO
2
is a promising option for a hydrophilic
filler in PES/SPEEK as it can ensure appropriate
hydration of the membrane during fuel cell operation.
The outcomes of the PES/SPEEK-TiO
2
composite
membranes indicate that the filler's morphological
features significantly impact the performance of the
membranes at elevated operating temperatures.
2 MATERIALS
The basics materials or polymers employed in this
study are eugenol and Poly ether ether ketone
obtained from Sigma Aldrich is subjected to a
sulfonation process involving the usage of sulfuric
ICATECH 2023 - International Conference on Advanced Engineering and Technology
174

acid, deionized water, and ice cubes. N-Methyl-2-
pyrrolidone (NMP) solvent from Merck is used. TiO
2
from Sigma Aldrich is utilized as an additive filler.
2.1 Polyeugenol Sulfonated (PES)
Preparation
PES was synthesized by applying the techniques
outlined by MuliawatI (20170, utilizing Sulfuric acid
(H
2
SO
4
).
2.2 Sulfonated Poly Ether Ether
Ketone (SPEEK)
The SPEEK polymer will be obtained through the
process of sulfonation reaction of PEEK and
following methods described by Jaafar (Jaafar,
Ismail, Matsuura, & Nagai, 2011).
2.3 Fabrication Membranes
The process of producing PES/SPEEK-TiO
2
involves
dissolving its constituents in a solvent via stirring
until complete dissolution. The resulting solution is
then heated at 90°C for 12 hours with continuous
magnetic stirring, Following this, the direct casting
method is utilized to transform it into a thin
membrane, then its dried at 800°C for 30 hours to
ensure its complete curing. To improve the
membrane's proton conductivity, it is soaked in 10M
H
2
SO
4
for 100 hours. Finally, the thickness of the
resulting membranes ranges between 0.2-0.3mm.
2.4 Characterization of the Membrane
Several techniques were utilized to analyze the ionic
properties of the membrane, such as:
2.4.1 Proton Conductivity
Electrochemical Impedance Spectroscopy was used
to measure the Proton conductivity membrane, its
was hydrated by soaking in 10 M Sulfuric acid for 36
hours, and then placed into a membrane clamping
chip and heated to temperatures ranging between 80
0
-
90
0
C. The analysis was performed by using the two-
probe method at frequencies ranging from 1-10
6
Heartz.
σ =L/(R x A) (1)
Equation (1) calculates, where σ represents the proton
conductivity in S/cm of the membrane. The
membrane's thickness is represented by the symbol L
and measured in centimeters (cm), while A represents
its surface area in cm
2
. The resistance value of the
membrane is represented by R in Ω.
2.4.2 Water and Methanol Uptake
To determine the membrane's water and methanol
uptake, it was observed under both dry and wet
conditions. The measurements were taken for both
water uptake (W
Upt
) and methanol uptake (M
Upt
). The
first step was to dry the membrane at 60°C for 18
hours and record its baseline weight. Afterward, the
membrane was soaked in either water or methanol for
a period of 36 hours until complete hydration was
achieved. Before being weighed again, any remaining
liquid present on the surface of the membrane was
wiped off using a tissue.
W
Upt
and M
Upt
(%) = 






 X 100% (2)
W
Upt
and M
Upt
were calculated using Equation (2),
W
dry
and W
wet
denotes the mass of the membrane
before soaking and after has been soaked in grams
represents the mass of the membrane.
2.4.3 Ion Exchange Capacity (IEC)
The titration method was used to determine the ion
exchange capacity (IEC) of the membrane. The
membrane was first dried at 60°C for 18 hours and
weighed. Then, it was immersed in a 100 mL solution
containing 1M NaCl to facilitate the exchange of H
+
ions with Na
+
ions. Phenolphthalein indicator was
added to the solution, which was then titrated with
0.01M NaOH until the equivalence point was
reached. Subsequently, the IEC was determined using
Equation (3).
Uptake (%) = 






 X 100% (3)
In Equation (3), In the titration process, M
NaOH
represents the molar concentration of NaOH used,
measured in mol/L. V
NaOH
represents the Volume and
W
dry
represents the dry mass of the membrane in
grams.
2.4.4 Water Contact Angle (WCA)
In order to assess the hydrophilicity and water uptake
of the membrane, the Water Contact Angle test
(WCA) using the OCA15 Pro by Data Physics,
membrane samples measuring (4 X 30) mm were
prepared in a dry and flat state and clamped securely
in a straight position. The sessile drop method was
employed during the test, and the angle between the
A Novel Polymer Electrolyte Membrane PES/SPEEK-TIO2 Potential for Direct Methanol Fuel Cell
175

water droplet and the membrane surface was
measured to determine the membrane's hydrophilic
characteristics.
2.4.5 Methanol Permeability
To determine the membrane's methanol permeability,
a two-compartment diffusion cell was employed. The
initial section (A) contained a methanol solution with
a concentration of 1 mole per liter, whereas the
second section (B) was occupied by water that had
been deionized. The flat and unmoistened membrane
was placed between the two sections. Within a time
frame of 2 hours, samples were taken from section B
every 20 minutes, using a pipette.
The extracted solutions were then examined using
High Performance Liquid Chromatography (HPLC).
P =

∆

∆






(4)
Equation (4) is utilized to determine the methanol
permeability of the membrane. P is expressed in units
of cm2.s-1 and is calculated by dividing the rate of
change of methanol concentration in compartment B
per unit time (mol.L-1.s-1), denoted by C_B/∆t, by L
multiplied by VB and divided by A multiplied by CA.
Here, L represents the thickness of the membrane in
cm, VB indicates the volume of water in compartment
B in cm3, A is the surface area of the membrane in
cm2, and CA denotes the concentration of methanol
in compartment A in mol/L.
2.4.6 Swelling Ratio (SR)
In order to evaluate the extent of swelling in the
membrane, its length is measured in both dry and wet
states. Initially, the membrane is subjected to drying
in an oven set at 60°C for a duration of 12 hours, and
its length is measured and recorded. Subsequently,
the membrane is soaked in deionized water for 36
hours until it attains complete hydration. After
removing the membrane from the water, any residual
droplets on its surface are wiped away with a tissue
before measuring its length.
SR = 






X 100% (5)
The SR (%) using Equation (5), which calculates the
percentage increase in length between the wet L
wet
and dry L
dry
states.
3 RESULTS
Table 1: Value of membrane properties.
Blend Membrane
Uptake of water
(%wt)
Uptake of methanol
(%wt)
Ratio of Swelling
(%)
Ion-exchange capacity
(mmol/g)
Contact Angle
(°)
20% PEE
K
5.1 6 5 0.7 88
20% SPEE
K
25.5 19 14.9 1.27 79
20% SPEEK – 3% TiO
2
49.7 31 13 1.8 68.91
20% SPEEK – 5% TiO
2
48.2 28.5 11 2.2 67.36
20% SPEEK – 7% TiO
2
38 28 8 2.1 67.23
20% SPEEK- 3% PES – optimum (5%) TiO
2
51.6 32 14 2.6 59.31
20% PEEK- 3% PES – optimum (5%) TiO
2
26.5 18 7 2.2 72.15
Nafion 117 19.3 41 16.4 0.98 80
Table 2: Membrane performance.
Membrane
Proton Conductivity
(S.cm
-1
)
Methanol Permeability
(×10
-7
cm
2
.s
-1
)
SPEEK 20% 0.0071 11
20% SPEEK – 3% TiO
2
0.00160 12
20% SPEEK – 5% TiO
2
0.00180 18
20% SPEEK – 7% TiO
2
0.00181 19
20% SPEEK- 3% PES – optimum (5%) TiO
2
0.00203 6
20% PEEK- 3% PES – optimum (5%) TiO
2
0.00043 8
Nafion
®
117
0.090 25
ICATECH 2023 - International Conference on Advanced Engineering and Technology
176

Tables 1: Value properties membrane and Table 2:
Membrane performance reveal that the
PES/SPEEK-TiO
2
membrane loading with 3%wt
PES, SPEEK 20%wt, and 5%wt TiO
2
is the most
suitable composition for PEM in DMFC. In order to
ensure that PEMs function effectively in DMFCs, it
is important to assess key properties such as Water
and methanol uptake demonstrate the exchange of
ions and methanol within the membrane,
respectively, while the swelling ratio assesses the
membrane's stability in aqueous solutions. IEC,
measured in milli equivalents per gram of polymer,
indicates the number of proton transfer sites. The
contact angle indicates whether the material is
hydrophilic or hydrophobic. Proton conductivity is
essential for proton-conducting membranes used in
fuel cells, and the proton transport mechanism can
be explained through various mechanisms such as
"proton hopping," "Grotthus mechanism,"
"diffusion mechanism," or "vehicular mechanism."
High water uptake, low methanol uptake, high IEC,
low swelling ratio, and a more hydrophilic contact
angle are essential factors for achieving optimal
performance of a membrane in a fuel cell. Creating
hydrophilic domains by increasing water uptake
promotes proton transport.
Excessive water uptake can result in swelling
and an increase in methanol permeability, which
can weaken the membrane's mechanical stability.
The water uptake and proton conductivity of the
membrane are affected by its IEC value, which is
determined by the number of sulfonic acid groups
in its chemical structure. Agglomerate formation
leads to a decrease in the IEC value as the filler
content increases.
Figure 2: FT-IR spectra of (1) PEEK, (2) PES, (3) SPEEK
and (4) PES/ SPEEK-TiO
2
membranes.
The FT-IR spectra of PEEK, PES, SPEEK, and
SPEEK/PES- TiO
2
membranes are presented in
Figure 2. The bands at 701 cm
-1
, 1075 cm
-1
, and
1270 cm
-1
signifies the existence of sulfonic acid
groups within the polymer, which play a critical role
in facilitating proton transfer across the
PES/SPEEK membrane structure. The wide
absorption band observed at 3600 cm
-1
provides
further proof of the connection between water
molecules and sulfonic acid groups, indicating their
interaction with each other. Additionally, the
stretching vibration of the sulfonate ester groups in
SPEEK is observed at 1365 cm
-1
, and the stretching
vibration at 1165 cm
-1
.of the C=O groups in
SPEEK and PES is observed at 1659 cm
-1
. The band
at 701 cm
-1
confirms the presence of TiO
2
in the
membrane. The FT-IR analysis demonstrates the
successful incorporation of sulfonic acid groups
into the polymer.
Figure 3: Thermo-Gravimetric Analysis (TGA).
The Thermogravimetric Analysis (TGA) results
depicted in Figure 3 shed light on the thermal
stability of the SPEEK/PES-TiO
2
membrane. The
TGA curve indicates that the membrane undergoes
three degradation stages, whereas PEEK
membranes experience only one. The first stage is
observed at about 100°C, resulting from the
evaporation of water molecules from the polymer.
The second stage occurs around 200°C, where the
NMP solvent evaporates, and the sulfonate groups
bound to the polymer are lost, as reported by
Abbasi, Antunes, and Velasco in 2015. The final
stage occurs before 500°C, suggesting that the
SPEEK/PES- TiO
2
membrane is ideal for high-
temperature applications, as its degradation
temperature is approximately 500°C. In summary,
the TGA results validate the membrane's
remarkable thermal stability and its potential for use
in high-temperature applications.
A Novel Polymer Electrolyte Membrane PES/SPEEK-TIO2 Potential for Direct Methanol Fuel Cell
177

Figure 4: SEM image of (A) 20% SPEEK– 3% TiO
2
, (B)
20% SPEEK – 5% TiO
2
, (C) 20% SPEEK – 7% TiO
2
, (D)
20% SPEEK/3% PES – 5% TiO
2
The roughness of the PES membrane is likely a
result of its inherent properties and its interaction
with the SPEEK and TiO2 filler. The Figure 4 SEM
images also reveal that the TiO2 filler is uniformly
dispersed throughout the SPEEK/PES- TiO
2
membrane, which suggests good compatibility
among the components. The smooth surface of the
SPEEK/PES- TiO
2
membrane may help reduce
contact resistance and improve proton conductivity,
making it well-suited for use in fuel cell applications.
.
Figure 5: Proton transport mechanism between PES,
SPEEK and TiO
2
.
Furthermore, the SPEEK/PES- TiO
2
membrane
exhibited superior methanol resistance compared to
the SPEEK/PES membrane without TiO
2
, which
can be attributed to the interaction between TiO
2
and PES, forming a barrier against methanol
permeation. This is a crucial feature for DMFCs as
it reduces the crossover of methanol from the anode
to the cathode, which can lead to a decrease in cell
performance. Therefore, the addition of TiO
2
not
only enhances proton conductivity but also
improves the membrane's resistance to methanol,
making it a highly promising material for DMFC
applications.
4 CONCLUSIONS
The solution casting method was used to prepare the
SPEEK/PES- TiO
2
membrane, and it was found to
be successful through SEM imaging, which
revealed its homogeneity.
Incorporating TiO
2
into
the SPEEK/PES membrane is expected to enhance
the number of proton transfer sites that are
available, The membrane's ability to absorb water
greatly aids in the creation of hydrophilic areas,
thereby promoting the transfer of protons. The
findings indicate that the PES/SPEEK- TiO
2
membrane has considerable potential as a PEM for
DMFC applications, offering higher proton
conductivity and lower methanol permeability than
the Nafion® 117 membranes. These results provide
a strong foundation for further research into
developing PEMs with superior properties and
performance for DMFCs. Additionally, Figure 5
illustrates the likely proton transport mechanism
involving PES, SPEEK, and TiO
2
in the membrane.
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