A novel membrane for DMFC - Na2Ti3O7 nanotubes/Nafion composite membrane

In this study, novel sodium titanate (Na₂Ti₃O₇) nanotube/Nafion^® composite membranes were prepared by a solution casting method. The properties of these composite membranes were studied using Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). Additionally, the water uptake, methanol permeability, proton conductivity, and selectivity of the composite membranes were measured to evaluate the applicability of these membranes in DMFCs. It was found that the addition of Na₂Ti₃O₇ nanotubes enhanced the water uptake and reduced the methanol permeability of the composite membranes. The proton conductivity and methanol permeability depend on the Na₂Ti₃O₇ nanotube content. Using the selectivity, the optimal nanotube contents was found to be 5 wt%. The new composite membrane was found to have significantly higher selectivity than a pure Nafion^® membrane and thus has good potential to outperform Nafion^® in DMFCs.     

Enhanced properties of SPEEK with incorporating of PFSA and barium strontium titanate nanoparticles for application in DMFCs

Novel blend nanocomposite proton‐exchange membranes were prepared using sulfonated poly (ether ether ketone) (SPEEK), perfluorosulfonic acid (PFSA), and Ba_0.9Sr_0.1TiO₃ (BST) doped‐perovskite nanoparticles. The membranes were evaluated by attenuated total reflection, X‐ray diffraction spectroscopy, water uptake, proton conductivity, methanol permeability, and direct methanol fuel cell test. The effect of two additives, PFSA and BST, were investigated. Results indicated that both proton conductivity and methanol barrier of the blend nanocomposite membranes improved compared with pristine SPEEK and the as‐prepared blend membranes. The methanol permeability and the proton conductivity of the blend membrane containing 6 wt% BST obtained 3.56 × 10^?7 cm² s^?1 (at 25 °C) and 0.110 S cm^?1 (at 80 °C), respectively. The power density value for the optimum blend nanocomposite membrane (15 wt% PFSA and 6 wt% BST) (54.89 mW cm^‐2) was higher than that of pristine SPEEK (31.34 mW cm^‐2) and SPF15 blend membrane (36.12 mW cm^‐2).     

Potential of sodium alginate/titanium oxide biomembrane nanocomposite in DMFC application

A proton exchange membrane was synthesized consuming a sodium alginate biopolymer as the matrix and titanium oxide as the nanofiller. The titanium oxide content varied from 5 to 25 wt%. The biomembrane nanocomposite performs better than the pristine sodium alginate membrane based on liquid uptake, methanol permeability, proton conductivity, ion exchange capacity, and oxidative stability outcomes. The unique properties of sodium alginate and titanium oxide lead to outstanding interconnections, thus producing new materials with great characteristics and enhanced performance. The highest proton conductivity achieved in this study is 17.3 × 10^‐3 S cm^‐1, which performed by SAT5 (25 wt%) membranes at 70°C. An optimal content of titanium oxide enhances the conductivity and methanol permeability of the membrane. Additionally, the hydrophilicity of pure sodium alginate is greatly reduced and achieves a good liquid uptake capacity and swelling ratio. The characteristics of the SA/TiO₂ biomembrane nanocomposite were determined with field emission scanning electron microscope, Fourier transform infrared, X‐ray diffraction, thermal gravimetric analysis/differential scanning calorimetry, and mechanical strength analysis.     

Improving the proton conductivity and water uptake of polybenzimidazole-based proton exchange nanocomposite membranes with TiO2 and SiO2 nanoparticles chemically modified surfaces

Poly [2,2′-(m-pyrazolidene)-5,5′-bibenzimidazole] (PPBI) was synthesized from pyrazole-3,5-dicarboxylic acid and 3,3′,4,4′-tetraaminobiphenyle (TAB) through polycondensation reaction in polyphosphoric acid (PPA) as reaction solvent. And polymer-grafted SiO₂ and TiO₂ nanoparticles were prepared through radical polymerization of 1-vinylimidazole and sulfonated vinylbenzene on the surface-vinylated nanoparticles. The polymer-grafted SiO₂ and TiO₂ nanoparticles were utilized as a functional additive to prepare PPBI/polymer-grafted SiO₂ and TiO₂ nanocomposite membranes. Imidazole and sulfonated vinylbenzene groups on the surface of modified nanoparticles forming linkages with PPBI chains, improved the compatibility between PPBI and nanoparticles, and enhanced the mechanical strength of the prepared nanocomposite membranes. The prepared nanocomposite membranes showed higher water uptake and acid doping levels comparing to PPBI. Also, after acid doping with phosphoric acid, nanocomposite membranes exhibited enhanced proton conductivity in comparison to the pristine PPBI and PPBI/un-modified SiO₂ and TiO₂ nanocomposite membranes. The enhancement in proton conductivity of nanocomposite membranes resulted from modified SiO₂ nanoparticles showed higher conductivity than modified TiO₂ nanoparticles. The above results indicated that the PPBI/modified SiO₂ and TiO₂ nanocomposite membranes could be utilized as proton exchange membranes for medium temperature fuel cells.     

Barrier properties of sulfonated polysulfone/layered double hydroxides nanocomposite membrane for direct methanol fuel cell operating at high methanol concentrations

High performing and cost effective nanocomposite membranes for DMFC application are synthesized by incorporating hygroscopic layered double hydroxides (LDH) particles into sulfonated polysulfone (sPSU). A significant improvement in the dimensional stability as well as in the water and methanol molecular dynamics of the sPSU_LDH composite membrane is observed in comparison with both pristine sPSU and Nafion 212. The strong electrostatic interaction occurring between positively charged LDH platelets and negatively charged polymer chains of sPSU alters the microstructure of the ionic domains, allowing an effective reduction of the methanol permeability whilst improving the proton conductivity. The methanol crossover measurements confirmed that sPSU_LDH membranes are able to withstand high methanol concentration without significant aftermath on the chemical stability of the electrolyte. The features enable the single DMFC assembled with the sPSU_LDH nanocomposite to achieve the remarkable power density of 150 mW cm⁻² at 80 °C in 5 M methanol solution.     

Sulfonated poly(ether ether ketone)/clay-SO3H hybrid proton exchange membranes for direct methanol fuel cells

A new type of sulfonated clay (clay-SO₃H) was prepared by the ion exchange method with the sulfanilic acid as the surfactant agent. The grafted amount of sulfanilic acid in clay-SO₃H was 51.8 mequiv. (100 g)⁻¹, which was measured by thermogravimetric analysis (TGA). Sulfonated poly(ether ether ketone) (SPEEK)/clay-SO₃H hybrid membranes which composed of SPEEK and different weight contents of clay-SO₃H, were prepared by a solution casting and evaporation method. For comparison, the SPEEK/clay hybrid membranes were produced with the same method. The performances of hybrid membranes for direct methanol fuel cells (DMFCs) in terms of mechanical and thermal properties, water uptake, water retention, methanol permeability and proton conductivity were investigated. The mechanical and thermal properties of the SPEEK membranes had been improved by introduction of clay and clay-SO₃H, obviously. The water desorption coefficients of the SPEEK and hybrid membranes were studied at 80 °C. The results showed that the addition of the inorganic part into SPEEK membrane enhanced the water retention of the membrane. Both methanol permeability and proton conductivity of the hybrid membranes decreased in comparison to the pristine SPEEK membrane. However, it was worth noting that higher selectivity defined as ratio of proton conductivity to methanol permeability of the SPEEK/clay-SO₃H-1 hybrid membrane with 1 wt.% clay-SO₃H was obtained than that of the pristine SPEEK membrane. These results showed that the SPEEK/clay-SO₃H hybrid membrane with 1 wt.% clay-SO₃H had potential usage of a proton exchange membrane (PEM) for DMFCs.     

Water-stable crosslinked sulfonated polyimide–silica nanocomposite containing interpenetrating polymer network

Sulfonated polyimide (SPI) interpenetrating polymer network (IPN) (IXSPI)–silica (SiO₂) nanocomposite membranes were fabricated as proton conducting solid electrolytes for fuel cells. Urethane acrylate non-ionomers (UANs) were used as dispersants to homogeneously distribute nanosized SiO₂ and, simultaneously, as crosslinkers to induce IPN structure formation. IXSPI–SiO₂ nanocomposite membranes showed high proton conductivity and hydrolytic stability, and low methanol permeability as compared with those of pristine SPI. Interestingly, the casting solvent for membrane fabrication influenced membrane performances, especially proton conductivity. In particular, dimethyl sulfoxide exhibited a strong interaction with sulfonic acid groups in the polymer matrix, which hindered them from spontaneously releasing protons and reduced the proton conductivity and electrochemical performances of the resulting membranes. Crosslinkers with long polyethylene oxide chains also contributed to improved proton conductivity and increased single cell performances.     

Nanocomposite membranes of surface-sulfonated titanate and Nafion® for direct methanol fuel cells

Various thiol and sultone groups were grafted onto the surface of titanate nanosheets to render organic sulfonic acid (HSO₃–) functionality. The nanocomposite membranes were cast together with Nafion^® using these materials as inorganic fillers. Nanocomposite membranes containing surface-sulfonated titanates showed higher proton conductivity than composite membranes containing untreated TiO₂ P25 particles. They showed better mechanical and thermal stability than Nafion alone. The methanol permeability of nanocomposite membranes decreased with increasing the content of the sulfonated titanate in the nanocomposite membranes. The relative permeability of methanol through these composite membranes with 2 and 5 M methanol solutions was reduced by up to 38 and 26%, respectively, relative to pristine Nafion 115 membranes. The membrane electrode assembly using Nafion/sulfonated titanate nanocomposite membranes exhibited up to 57% higher power density than the assembly containing a pristine Nafion membrane under typical operating conditions of direct methanol fuel cells.     

Nafion/histidine functionalized carbon nanotube: High-performance fuel cell membranes

Here we show preparation and characterization of a new type of composite membrane based on Nafion^®/histidine modified carbon nanotube by imidazole groups (Im-CNT), for direct methanol fuel cell (DMFC) applications. Due to the presence of this imidazole-based amino acid on the surface of CNT, new electrostatic interactions can be formed in the interface of Nafion^® and Im-CNT. Physical characteristics of these nanocomposite membranes are investigated by water uptake, methanol permeability, ion exchange capacity, proton conductivity, as well as fuel cell performance results.     

Poly(vinyl alcohol)/sulfated β-cyclodextrin for direct methanol fuel cell applications

We report a composite membrane based on poly(vinyl alcohol) and sulfated β-cyclodextrin in this paper. TGA and SEM tests provide direct evidence of the thermal stability and the uniform structure of the composite membranes. The performances of the composite membranes are investigated in terms of swelling behavior, methanol permeability and proton conductivity as function of sulfated β-cyclodextrin content. We find that the introduction of sulfated β-cyclodextrin can reduce water uptake. The temperature dependence of proton conductivity reveals that the proton conducting activation energy of the composite membranes is similar to that of Nafion 115, in other words, both the vehicle and Grotthus mechanisms are assumed to be responsible for the composite membranes’ proton transfer. Methanol permeability decreases as the methanol feed concentration increases from 2 M to 20 M. Both proton conductivity and methanol permeability increases with increasing sulfated β-cyclodextrin. The selectivity of the composite membranes defined as the ratio of proton conductivity to methanol permeability obtains the maximum of 1.710 × 10⁴ S s cm⁻³ at the composition of 17 wt.% sulfated β-cyclodextrin. The MEAs fabricate with these membranes are tested, no distinct change occurred to the composite membranes after the MEAs operating for 288 h. These data indicates the chemical and electrochemical stability of the membranes and their potential application in direct methanol fuel cells.     

Preparation of polysiloxane/perfluorosulfonic acid nanocomposite membranes in supercritical carbon dioxide system for direct methanol fuel cell

In this work, polysiloxane-modified perfluorosulfonic acid (PFSA) membranes were prepared by a directed sol–gel synthesis method with (3-mercaptopropyl) methyldimethoxysilane (MPMDMS) as the precursor of silicon alkoxide in the supercritical carbon dioxide (Sc-CO₂) system. Contents of polysiloxane in the modified PFSA membranes were varied according to the added amount of precursor MPMDMS. The chemical and physical properties of these modified PFSA membranes were characterized by using attenuated total reflection-infrared spectra, X-ray diffraction, thermogravimetric analysis, universal testing machine, scanning electron microscopy and transmission electron microscope. The measurement results indicated that the polysiloxane particles were not restricted in the ion clusters and well dispersed in the PFSA membrane with ordered size of about 80–100 nm. In the meanwhile, the polysiloxanes have been incorporated into the hydrophobic fluorocarbon backbone regions and interacted with C–F backbones of PFSA polymers. Dimensional stability of the modified PFSA membrane was improved after the impregnation by using Sc-CO₂. The modified membranes almost can remain the same high tensile strength as the pristine membrane. Performance of these modified membranes was evaluated in terms of proton conductivity and methanol permeability. The highest selectivity value (ratio of proton conductivity to methanol permeability) of the modified membrane was about 75.6% higher than that of pristine PFSA membrane because of its higher proton conductivity and lower methanol permeability. All the results indicated that this novel synthesis method in Sc-CO₂ system is a promising method to improve the properties of PFSA membrane for direct methanol fuel cell application.     

Preparation and properties of epoxy-based cross-linked sulfonated poly(arylene ether ketone) proton exchange membrane for direct methanol fuel cell applications

Sulfonated poly(arylene ether ketone) bearing pendant carboxylic acid group (C-SPAEK) had been prepared for direct methanol fuel cell applications, and subsequently cross-linked by a thermal curing reaction using hexafluoro-bisphenol-A novolac epoxy resin (HFANER) as a cross-linker. The cross-linked network structure caused significant enhancement in the mechanical properties and oxidative stability. Meanwhile, water uptake, swelling ratio and methanol permeability substantially decreased with increasing the content of cross-linker. Notably, the water uptake of C-SPAEK was 506.9% at 80 °C, but after cross-linking, Cr-SPAEK-17 exhibited a water uptake of 32.3%. Meanwhile, a 12.1% of swelling ratio was obtained which was lower than that of Nafion 117 (17.2%). Although the proton conductivities of the cross-linked membranes were lower than that of the pristine membrane, the higher selectivity defined as the proton conductivity to methanol permeability was obtained for the cross-linked membranes.     

Composite membranes based on sulfonated poly(aryl ether ketone)s containing the hexafluoroisopropylidene diphenyl moiety and poly(amic acid) for proton exchange membrane fuel cell application

Composite membranes based on sulfonated poly(aryl ether ketone)s containing the hexafluoroisopropylidene diphenyl moiety and poly(amic acid) with oligoaniline in the main chain have been prepared and immersed in H₃PO₄ to obtain acid-doped composite films. As expected, the water uptake values and methanol permeability of the composite membranes decrease with the increase of the weight fraction of PAA in the membrane matrix. Notably, the SPEEK-6F/PAA-15 shows a water uptake of 13.2% and a methanol permeability of 0.9 × 10⁻⁷ cm² s⁻¹, which are much lower than those of the Nafion (28.6% and 15.5 × 10⁻⁷ cm² s⁻¹, respectively). Although the proton conductivities decrease after the addition of PAA, higher selectivity values are obtained with the composite membranes. Therefore, the SPEEK-6F/PAA blend membranes, with the improved proton conductivity, methanol resistance and good thermal stability, can be used as a good alternative for proton conductive membranes with potential application in proton exchange membrane fuel cells (PEMFCs).     

The relationship between proton conductivity and water permeability in composite carboxylate/sulfonate perfluorinated ionomer membranes

Composite carboxylate/sulfonate Nafion^® films were prepared with different ratios of anion equivalents as a test of the relationship between proton conductivity and water permeability in perfluorinated ionomers. Substitution of carboxylate groups for sulfonate groups dramatically reduced water permeability and modestly reduced proton conductivity in the films. Small angle X-ray scattering (SAXS) was used to probe the polymer microstructure and showed that with up to 20% carboxylate equivalents, the size of hydrated ionic domains within the ionomer remains constant. Water sorption measurements showed little decrease in water uptake with increased carboxylate functionality, supporting the SAXS data. Methanol/water permeability experiments showed that the carboxylate moieties slow the diffusion of both water and methanol, with no permselectivity of water. Results indicate that the proton transport mechanism is altered by addition of carboxylic acid. As such, the composites may show interesting behavior in H₂/O₂ and direct methanol fuel cells. It is proposed that permeability and conductivity measurements may provide an inexpensive and simple screening tool for early evaluation of new experimental proton exchange membranes.     

Fabrication of novel proton exchange membranes for DMFC via UV curing

The radiation hardening of various UV curable resins provides a simple but powerful method to fabricate thin films or membranes with desirable physical and chemical properties. In this study, we proposed to use this method to fabricate a novel proton exchange membrane (PEM) for direct methanol fuel cells (DMFC) with good mechanical, transport and stability properties. The PEM was prepared by crosslinking a mixture of a photoinitiator, a bifunctional aliphatic urethane acrylate resin (UAR), a trifunctional triallyl isocyanate (TAIC) crosslinker and tertrabutylammonium styrenesulfonate (SSTBA) to form a uniform network structure for proton transport. Key PEM parameters such as ion exchange capacity (IEC), water uptake, proton conductivity, and methanol permeability were controlled by adjusting the chemical composition of the membranes. The IEC value of the membrane was found to be an important parameter in affecting water uptake, conductivity as well as the permeability of the resulting membrane. Plots of the water uptake, conductivity, and methanol permeability vs. IEC of the membranes show a distinct change in the slope of their curves at roughly the same IEC value which suggests a transition of structural changes in the network. It is demonstrated that below the critical IEC value, the membrane exhibits a closed structure where hydrophilic segments form isolated domains while above the critical IEC value, it shows an open structure where hydrophilic segments are interconnected and form channels in the membrane. The transition from a closed to an open proton conduction network was verified by the measurement of the activation energy of membrane conductivity. The activation energy in the closed structure regime was found to be around 16.5 kJ mol⁻¹ which is higher than that of the open structure region of 9.6 kJ mol⁻¹. The membranes also display an excellent oxidative stability, which suggests a good lifetime usage of the membranes. The proton conductivities and the methanol permeabilities of all membranes are in the range of 10⁻⁴ to 10⁻² S cm⁻¹ and 10⁻⁸ to 10⁻⁷ cm² s⁻¹, respectively, depending on their crosslinking density. The membranes show great selectivity compared with those of Nafion^®. The possibility of using this PEM for DMFC devices is suggested.     

Intermolecular ionic cross-linked proton conducting electrolyte membranes derived from branched sulfonated poly(ether ether ketone)s with benzoxazole pendants

A series of novel branched sulfonated poly(ether ether ketone)s containing intermolecular ionic cross-linkable groups, benzoxazole groups, have been prepared for direct methanol fuel cells. The benzoxazole groups are grafted onto the polymer chain via a thiol-ene click chemistry reaction. The expected structures of the copolymers are confirmed by ¹H NMR and Fourier transform infrared spectroscopy. Compared with the unmodified polymer membrane, the ionic cross-linked membranes show enhanced thermal and mechanical properties. We also investigate the changes in water uptake, proton conductivity and chemical stability. The dense membrane structures formed by branching and the interactions between sulfonic acid and benzoxazole groups make a great contribution to the improvements of dimensional stability and methanol resistance property. Although the proton conductivities of the ionic cross-linked membranes are lower than the pristine membrane, the selectivities are much higher. The results show that the novel copolymers in this study are possible potential candidate materials for proton electrolyte membrane.     

Cross-linked membranes based on sulfonated poly (ether ether ketone) (SPEEK)/Nafion for direct methanol fuel cells (DMFCs)

A series of cross-linked membranes based on SPEEK/Nafion have been prepared to improve methanol resistance and dimension stability of SPEEK membrane for the usage in the direct methanol fuel cells (DMFCs). Sulfonated diamine monomer is synthesized and used as cross-linker to improve the dispersion of Nafion in the composite membranes and decrease the negative effect of cross-linking on proton conductivity of membranes. FT-IR analysis shows that the cross-linking reaction is performed successfully. The effects of different contents of Nafion on the properties of cross-linked membranes are investigated in detail. All the cross-linked membranes show lower methanol permeability and better dimensional stability compared with the pristine SPEEK membrane. SPEEK-N30 with the 30 wt % Nafion shows a methanol permeability of 0.73 × 10⁻⁶ cm² s⁻¹ and a water uptake of 24.4% at 25 °C, which are lower than those of the pristine membrane. Meanwhile, the proton conductivity of SPEEK-N30 still remains at 0.041 S cm⁻¹ at 25 °C, which is comparable to that of the pristine SPEEK membrane. All the results indicate that these cross-linked membranes based on SPEEK/Nafion show good prospect for the use as proton exchange membranes.     

Evaluation of Quaternized polyvinyl alcohol/graphene oxide-based membrane towards improving the performance of air-breathing passive direct methanol fuel cells

Graphene oxide (GO) nanosheets are introduced to a Quaternized polyvinyl alcohol (QPVA) polymer matrix to obtain an anion exchange membranes (AEMs) for application of fuel cells. QPVA/GO nanocomposite membranes provide desirable properties such as low fuel uptake and permeability, excellent ionic conductivity, and cell performance, all of which are favorable for AEMs based on our previous works. Passive direct methanol fuel cells (DMFCs) are recognized as suitable technologies for use in portable devices. Nevertheless, the commercialization of DMFCs remains restricted due to a number of issues related to the conventional membrane; one of these issues is high fuel crossover problems due to high fuel uptake and permeability of Nafion membrane. This study aimed to expand the potential applications of QPVA/GO nanocomposite membranes in air-breathing passive DMFCs. The ionic conductivity, methanol uptakes (MUs), and permeabilities of self-synthesis QPVA/GO nanocomposites are examined to evaluate the ability to operate in methanol atmosphere. At 30°C, the ionic conductivity of the membranes reached 1.74 × 10⁻² S cm⁻¹. The MUs and permeabilities were as low as 35% and 7.6 × 10⁻⁷ cm² s⁻¹, respectively. The performance of air-breathing passive DMFCs bearing QPVA/GO nanocomposite membrane is much higher compared to conventional membranes. The maximum power density of air-breathing passive DMFCs was achieved 27.2 mW cm⁻² under the optimum condition of 2 M methanol + 4 M KOH at 70°C. Single-cells could be sustained for 1000 hours. This article is the first to optimize and highlight the performance air-breathing passive DMFCs by using a QPVA-based membrane.     

SO2 permeability and proton conductivity of sPEEK membranes for SO2-depolarized electrolyzer

The SO₂ transport properties of Nafion^® and sPEEK membranes were measured using an electrochemical reaction cell to investigate their application in the electrochemical hybrid sulfur process. The permeability of SO₂ in the membranes was determined from a combined theory based on Faraday's law and Fick's law where the electrochemical reaction rate of SO₂ in the downstream membrane is the same as its diffusion flux through the membrane. Both Nafion^® and sPEEK membranes show higher SO₂ diffusion coefficients at higher temperatures. For sPEEK membranes, increasing the degree of sulfonation resulted in increasing permeability, as more water was imbibed in the membranes with higher degrees of sulfonation. Activation energy was extracted from the temperature-dependence of the diffusion coefficients for both membranes. The sPEEK membranes exhibited similar diffusion coefficients to those of Nafion^®, even at high sulfonation degrees of 70%. Besides SO₂ permeability, proton conductivity and mechanical properties were measured for comparison between the 2 polymer membranes. Although the proton conductivity of the sPEEK was slightly lower than the Nafion^® membrane, it was very competitive considering its higher mechanical strength and much lower cost.     

Investigation of physical properties and cell performance of Nafion/TiO2 nanocomposite membranes for high temperature PEM fuel cells

Synthesis and characterization of Nafion/TiO₂ membranes for proton exchange membrane fuel cell (PEMFC) operating at high temperatures were investigated in this study. Nafion/TiO₂ nanocomposite membranes have been prepared by in-situ sol–gel and casting methods. In the sol–gel method, preformed Nafion membranes were soaked in tetrabutylortotitanate (TBT) and methanol solution. In order to compare synthesis methods, a Nafion/TiO₂ composite membrane was fabricated with 3 wt.% of TiO₂ particles by the solution casting method. The structures of membranes were investigated by Differential Scanning Calorimetry (DSC), Scanning Electron Microscopy (SEM), and Energy Dispersive X-Ray Analysis (EDXA). Also, water uptake and proton conductivity of modified membranes were measured. Furthermore, the membranes were tested in a real PEMFC. X-Ray spectra of the composite membranes indicate the presence of TiO₂ in the modified membranes. In case of the same doping level, sol–gel method produces more uniform distribution of Ti particles in Nafion/TiO₂ composite membrane than the ones produced by casting method. Water uptake of Nafion/TiO₂ membrane with 3 wt.% of doping level was found to be 51% higher than that of the pure Nafion membrane. EIS measurements showed that the conductivity of modified membranes decreases with increasing the amount of doped TiO₂. Finally, the membrane electrode assembly (MEA) prepared from Nafion/Titania nanocomposite membrane shows the highest PEMFC performance in terms of voltage vs. current density (V–I) at high temperature (110 °C) which is the main goal of this study.