similar to the average result of the same setting. Thus, it is
evident that there are significant challenges remaining in the
development of SOFC in a single step. The increase in TPB
density by controlling the anode morphology (e.g. by
adjusting the length of finger-like voids and enhancing the
porosity) might lead to improved MT-SOFC performance.
Under those circumstances, a comprehensive study on the
fabrication of SOFC is important in order to produce
defect-free hollow fibers with the desired morphologies that
maintain high mechanical strength, decent tightness properties, and sufficient anode porosity to produce highperformance MT-SOFCs.
3.2 Performance of Proton Exchange Membrane
Fuel Cell
Improvement of PEMFC performance is mainly targeted to
be achieved by solving the main issues faced by the development of PEMFC which are (1) lowering cost, (2) water
management system, (3) proton conductivity at high temperature, (4) lower gas crossover, and (5) improved thermal
stability and mechanical and chemical strength (Peighambardoust et al. 2010; Majlan et al. 2018). Effort on lowering
the cost is targeted to be achieved by developing lower cost
material compared to the current traditional fluorinated
membrane and by developing lower cost catalyst other than
Pt and Rh while other developments are targeted at
improvement of the cathode layer. Table 2 summarizes few
literature that address the development of new electrolyte
membrane and the resulted maximum power density
achieved by the studies.
All of the studies highlighted in Table 2 involved doping
or adding functional layer to the existing membrane to
enhance the properties. This in effect highlighted the rise in
the usage of composite membrane in PEMFC as opposed to
single membrane. In addition, analysis of EIS in PEM allows
the identification of (1) layers in fuel cell that occurs due to
the different processes such as mass transport process and
polarization effect, (2) effect of different layer to the total
resistance and impedance of the cell, and (3) microscopic
detail such as change in granule size that affects the impedance and performance of the cell (Pivac and Barbir 2016).
Zhiani et al. (2016) studied the effect of thermal and pressure
stress on PEM and found that PEM running with membrane
electrode assembly (MEA) conditioned under low stress
resulted in higher performance, peaking at 1.6 W cm
−2
compared to MEA conditioned under high stress. From the
EIS equivalent circuit, it was postulated that the higher
performance may be the result of extension of the
triple-phase boundary in MEA that increases the reactive
area for reaction.
For PEM, inductive phenomenon in EIS at high frequency was known to be caused simply by the effect of the
wire and cable setup of the cell (Pivac and Barbir 2016).
However, inductive effect at low frequency might suggest
the possibilities of side reactions occurring in the cell
between intermediate species, carbon monoxide poisoning
of the cell or water movement across the layer. From
equivalent circuit of EIS in PEM, the total resistance, R T of
the cell can be determined together with the contribution
resistance by charge transfer, R CT and ionic resistance R ion
inside the cell (Moghaddam and Easton 2018). Low R CT and
high R ion may significantly impact performance of MEA and
R T value may be used as basic reference to assess the performance of Nafion-based PEMFC.
EIS has also been investigated to function as online
measurement tool to study and monitor the effect of load
current, air humidification rate, and hydrogen flow rate effect
on the online performance of PEM to be used in electric
vehicle (Depernet et al. 2016). In that study, the DC bus
from the vehicle is connected to inverter and to DC/AC/DC
power converter and the EIS spectra was obtained at discrete
and few frequency (as opposed to cycling from low- to
high-frequency AC) and the resulting equivalent circuit was
generated and compared with ex-situ equivalent circuit. The
study found that online EIS is comparable with ex-situ offline EIS and hence can be used as reliable tool to monitor the
performance of PEM online.
3.3 Performance of Direct Methanol Fuel Cell
The focus of DMFC researches is mainly targeted to solve
the issue in Sect. 2.3. Similar to PEMFC, the improvement
of the electrolyte layer is also one of the main focuses of
studies in DMFC. However, since DMFC also faced the
problem with methanol crossover, this issue added another
complexity in DMFC research as compared to PEMFC. Few
research that are presented with maximum power density
obtained in the studies are given in Table 3.
The studies are mainly done to resolve the issues by
focusing on high temperature use of DMFC, methanol
crossover and by managing water and gas flow in the cell and
the catalyst to improve the performance of the DMFC (Kim
et al. 2015; Radenahmad et al. 2016; Zainoodin et al. 2010;
Li et al. 2013; Ong et al. 2017). Overall output of DMFCs
relies on several variables, the most significant of which are:
(i) anode’s electrocatalytic activity, (ii) ionic conductivity
and methanol crossover strength of the proton conductive
membrane, and (iii) water management on the cell’s cathode
side (flow-field and back design function). As mentioned
earlier, optimization of various DMFC parts can lead to a
significant increase in power density and fuel utilization.
118
S. M. Jamil et al.
evident that there are significant challenges remaining in the
development of SOFC in a single step. The increase in TPB
density by controlling the anode morphology (e.g. by
adjusting the length of finger-like voids and enhancing the
porosity) might lead to improved MT-SOFC performance.
Under those circumstances, a comprehensive study on the
fabrication of SOFC is important in order to produce
defect-free hollow fibers with the desired morphologies that
maintain high mechanical strength, decent tightness properties, and sufficient anode porosity to produce highperformance MT-SOFCs.
3.2 Performance of Proton Exchange Membrane
Fuel Cell
Improvement of PEMFC performance is mainly targeted to
be achieved by solving the main issues faced by the development of PEMFC which are (1) lowering cost, (2) water
management system, (3) proton conductivity at high temperature, (4) lower gas crossover, and (5) improved thermal
stability and mechanical and chemical strength (Peighambardoust et al. 2010; Majlan et al. 2018). Effort on lowering
the cost is targeted to be achieved by developing lower cost
material compared to the current traditional fluorinated
membrane and by developing lower cost catalyst other than
Pt and Rh while other developments are targeted at
improvement of the cathode layer. Table 2 summarizes few
literature that address the development of new electrolyte
membrane and the resulted maximum power density
achieved by the studies.
All of the studies highlighted in Table 2 involved doping
or adding functional layer to the existing membrane to
enhance the properties. This in effect highlighted the rise in
the usage of composite membrane in PEMFC as opposed to
single membrane. In addition, analysis of EIS in PEM allows
the identification of (1) layers in fuel cell that occurs due to
the different processes such as mass transport process and
polarization effect, (2) effect of different layer to the total
resistance and impedance of the cell, and (3) microscopic
detail such as change in granule size that affects the impedance and performance of the cell (Pivac and Barbir 2016).
Zhiani et al. (2016) studied the effect of thermal and pressure
stress on PEM and found that PEM running with membrane
electrode assembly (MEA) conditioned under low stress
resulted in higher performance, peaking at 1.6 W cm
−2
compared to MEA conditioned under high stress. From the
EIS equivalent circuit, it was postulated that the higher
performance may be the result of extension of the
triple-phase boundary in MEA that increases the reactive
area for reaction.
For PEM, inductive phenomenon in EIS at high frequency was known to be caused simply by the effect of the
wire and cable setup of the cell (Pivac and Barbir 2016).
However, inductive effect at low frequency might suggest
the possibilities of side reactions occurring in the cell
between intermediate species, carbon monoxide poisoning
of the cell or water movement across the layer. From
equivalent circuit of EIS in PEM, the total resistance, R T of
the cell can be determined together with the contribution
resistance by charge transfer, R CT and ionic resistance R ion
inside the cell (Moghaddam and Easton 2018). Low R CT and
high R ion may significantly impact performance of MEA and
R T value may be used as basic reference to assess the performance of Nafion-based PEMFC.
EIS has also been investigated to function as online
measurement tool to study and monitor the effect of load
current, air humidification rate, and hydrogen flow rate effect
on the online performance of PEM to be used in electric
vehicle (Depernet et al. 2016). In that study, the DC bus
from the vehicle is connected to inverter and to DC/AC/DC
power converter and the EIS spectra was obtained at discrete
and few frequency (as opposed to cycling from low- to
high-frequency AC) and the resulting equivalent circuit was
generated and compared with ex-situ equivalent circuit. The
study found that online EIS is comparable with ex-situ offline EIS and hence can be used as reliable tool to monitor the
performance of PEM online.
3.3 Performance of Direct Methanol Fuel Cell
The focus of DMFC researches is mainly targeted to solve
the issue in Sect. 2.3. Similar to PEMFC, the improvement
of the electrolyte layer is also one of the main focuses of
studies in DMFC. However, since DMFC also faced the
problem with methanol crossover, this issue added another
complexity in DMFC research as compared to PEMFC. Few
research that are presented with maximum power density
obtained in the studies are given in Table 3.
The studies are mainly done to resolve the issues by
focusing on high temperature use of DMFC, methanol
crossover and by managing water and gas flow in the cell and
the catalyst to improve the performance of the DMFC (Kim
et al. 2015; Radenahmad et al. 2016; Zainoodin et al. 2010;
Li et al. 2013; Ong et al. 2017). Overall output of DMFCs
relies on several variables, the most significant of which are:
(i) anode’s electrocatalytic activity, (ii) ionic conductivity
and methanol crossover strength of the proton conductive
membrane, and (iii) water management on the cell’s cathode
side (flow-field and back design function). As mentioned
earlier, optimization of various DMFC parts can lead to a
significant increase in power density and fuel utilization.
118
S. M. Jamil et al.