Self-humidifying nanocomposite membranes based on sulfonated poly(ether ether ketone) and heteropolyacid supported Pt catalyst for fuel cells

In the present study, the self-humidifying nanocomposite membranes based on sPEEK and Cs_2.5H_0.5PW₁₂O₄₀ supported Pt catalyst (Pt-Cs_2.5H_0.5PW₁₂O₄₀ catalyst or Pt-Cs_2.5) and their performance in proton exchange membrane fuel cells with dry reactants has been investigated. The XRD, FTIR, SEM-EDXA and TEM analysis were conducted to characterize the catalyst and membrane structure. The ion exchange capacity (IEC), water uptake and proton conductivity measurements indicated that the sPEEK/Pt-Cs_2.5 self-humidifying nanocomposite membranes have higher water absorption, acid and proton-conductive properties compared to the plain sPEEK membrane and Nafion-117 membrane due to the highly hygroscopic and acidy properties of Pt-Cs_2.5 catalyst. The single cells employing the sPEEK/Pt-Cs_2.5 self-humidifying nanocomposite membranes exhibited higher cell OCV values and cell performances than those of plain sPEEK membrane and Nafion-117 membrane under dry or wet conditions. Furthermore, the sPEEK/Pt-Cs_2.5 self-humidifying nanocomposite membranes showed good water stability in aqueous medium. After investigation of several membranes such as sPEEK and sPEEK/Pt-Cs_2.5 membranes, the self-humidifying nanocomposite membrane with sulfonation degree of 65.12% for its sPEEK and 15 wt.% of catalyst with 1.25 wt.% Pt within catalyst was found to be the best proton exchange membrane for fuel cell applications. This self-humidifying nanocomposite membrane has a higher single cell performance than the Nafion-117 which was frequently used as a proton exchange membrane for fuel cell applications.     

Fabrication and evaluation of Nafion nanocomposite membrane based on ZrO2–TiO2 binary nanoparticles as fuel cell MEA

Synthesis and characterization of nanocomposite membranes for proton exchange membrane fuel cell (PEMFC) operating at different temperatures and humidity were investigated in this study. Recast Nafion composite membrane with ZrO₂ and TiO₂ nanoparticles with 75 nm in mean size diameter, prepared for PEM fuel cells. Nafion/TiO₂ composite membranes have been also fabricated by in-situ sol–gel method. However, fine particles of the ZrO₂ were synthesized and Nafion/ZrO₂ composite membrane were produced by blending a 5% (w/w) Nafion-water dispersion with the inorganic compound. All nanocomposite membranes demonstrated higher water retention in comparison with unmodified membranes. Proton conductivity increased with increasing ZrO₂ content while TiO₂ additive (with mean size of 25 nm) enhanced water retention. Subsequently, structures of the membranes were investigated by Atomic Force Microscopy (AFM), Scanning Electron Microscopy (SEM) as well as X-Ray Diffraction (XRD). In addition, water uptake and proton conductivity of the modified membranes were also measured. The nanocomposite membrane was tested in a 25 cm² commercial single cell at the temperature range of 80–110 °C and in humidified H₂/O₂ under different relative humidity (RH) conditions. The membrane electrode assembly (MEA) prepared from Nafion/TiO₂, ZrO₂ presented highest PEM fuel cell performance in respect of I–V polarization under condition of 110 °C, 0.6 V and 30% RH and 1 atm.     

Adaptive neuro‐fuzzy inference system and artificial neural network modeling of proton exchange membrane fuel cells based on nanocomposite and recast Nafion membranes

In this study, a proton exchange membrane fuel cell (PEMFC) is modeled by multilayer perceptron neural network (MLPNN), RBF neural network (RBFNN), and adaptive neuro‐fuzzy inference system (ANFIS). Experimental data are obtained on the basis of the fabricated membrane‐electrode assembly (MEA) responses using prepared nanocomposite and recast Nafion membranes in the PEMFC. Four parameters including cell temperature, inlet gas temperature, current density, and inorganic additive percent are used as inputs, and the cell voltage is considered as the output. The results show that there is no considerable discrepancy between the RBFNN accuracy (R = 0.99554) and the MLPNN accuracy (R = 0.99609) for the performance prediction. The required time for developing the RBFNN model is significantly lower than the MLPNN model. A variety of ANFIS structure is explored to approximate the behavior of the system. The effect of cell and inlet gas temperatures on the PEMFC performance is investigated by the ANFIS developed model. Predicted polarization and power–current behavior by the ANFIS for the MEA prepared by the recast Nafion and the nanocomposite membranes at the cell temperatures 50 °C to110°C are in high agreement with the experimental data. Predicted data by the ANFIS show that because of the property of Cs_2.5H_0.5PW₁₂O₄₀ additive for retaining water, much higher current density and power density at the same voltage are achieved for the nanocomposite membrane compared with the recast Nafion membrane in the PEMFC. Copyright © 2011 John Wiley & Sons, Ltd.     

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.     

Role of UV irradiated Nafion in power enhancement of hydrogen fuel cells

The influence of optimum UV ray exposure of pristine Nafion polymer membranes on the improvement of proton conductivity and hydrogen fuel cell performance has been examined. Nafion membranes with thickness 183  μm (117), 90  μm (1035), 50  μm (212) and 25  μm (211) were irradiated with ultraviolet rays with doses in the range 0–250 mJ cm^?2 and their proton conductivities have been measured with standard method. The Nafion membranes have also been studied by measuring their water uptake, swelling-ratios and porosity using standard procedures. Hydrogen fuel cells with dual serpentine microchannels with active area 1.9 x 1.6 cm^-2 were assembled with anode gas diffusion layer, Nafion membrane, cathode gas diffusion layer and other components. An external humidifier was used to humidify hydrogen for the fuel cell. The experimental Results have shown an increase in the value of Nafion proton conductivity with an optimum UV irradiation which depends on the thickness of Nafion membrane: the optimum doses for peak proton conductivity were 196mJ/cm^?2 for Nafion 117, 190mJ/cm^?2for Nafion 1035, 180mJ/cm^?2 for Nafion 212 and 160mJ/cm^?2 for Nafion 211. This enhancement of proton conductivity is because of the optimal photo-crosslinking of –SO₃H groups in Nafion. This causes optimum pore-size in Nafion thereby facilitating increased proton-hopping between –SO₃H sites in Nafion. Hydrogen fuel cells were developed with pristine as well as with optimal UV irradiated Nafion with thicknesses of 90 and 50  μm. The polarization plots obtained for these devices showed an increase in power densities approximately by a factor of 1.8–2.0 for devices with optimally UV irradiated Nafion. These results indicate that optimal UV irradiation of Nafion is an excellent technique for enhancing power output of hydrogen fuel cells.     

Cesium substituted 12-tungstophosphoric (CsxH3−xPW12O40) loaded on ceria-degradation mitigation in polymer electrolyte membranes

A novel multifunctional catalyst Cs_xH_3−xPW₁₂O₄₀/CeO₂ was prepared to mitigate the free radical attack to membranes in fuel cell environment. Cs_xH_3−xPW₁₂O₄₀/CeO₂ nanoparticles synthesized by solution-based hydrothermal method and two-step impregnation method were dispersed uniformly into the Nafion^® resin, and then the composite membrane was prepared using solution-cast method. The particles prepared were characterized by X-ray powder diffraction (XRD), TEM and FT-IR to evaluate the crystallite size, distribution of the nanopaticles and the crystal structure. The membrane degradation was investigated via ex situ Fenton test and in situ open circuit voltage (OCV) accelerated test. In the durability tests, the fluoride emission rate (FER) reduced nearly one order of magnitude by adding Cs_xH_3−xPW₁₂O₄₀/CeO₂ nanoparticles into the Nafion membrane, suggesting that Cs_xH_3−xPW₁₂O₄₀/CeO₂ catalyst has a promising application to greatly improve the proton exchange membrane (PEM) durability.     

Improvement of PEMFC performance with Nafion/inorganic nanocomposite membrane electrode assembly prepared by ultrasonic coating technique

Membrane electrode assemblies with Nafion/nanosize titanium silicon dioxide (TiSiO₄) composite membranes were manufactured with a novel ultrasonic-spray technique and tested in proton exchange membrane fuel cell (PEMFC). Nafion/TiO₂ and Nafion/SiO₂ nanocomposite membranes were also fabricated by the same technique and their characteristics and performances in PEMFC were compared with Nafion/TiSiO₄ mixed oxide membrane. The composite membranes have been characterized by thermogravimetric analysis, scanning electron microscopy, X-ray diffraction, water uptake, and proton conductivity. The composite membranes gained good thermal resistance with insertion of inorganic oxides. Uniform and homogeneous distribution of inorganic oxides enhanced crystalline character of these membranes. Gas diffusion electrodes (GDE) were fabricated by Ultrasonic Coating Technique. Catalyst loading was 0.4 mg Pt/cm² for both anode and cathode sides. Fuel cell performances of Nafion/TiSiO₄ composite membrane were better than that of other membranes. The power density obtained at 0.5 V at 75 °C was 0.456 W cm⁻², 0.547 W cm⁻², 0.477 W cm⁻² and 0.803 W cm⁻² for Nafion, Nafion/TiO₂, Nafion/SiO₂, and Nafion/TiSiO₄ composite membranes, respectively.     

An enhanced proton conductivity and reduced methanol permeability composite membrane prepared by sulfonated covalent organic nanosheets/Nafion

Sulfonated covalent organic nanosheets (SCONs) with a functional group (−SO₃H) are effective at reducing ion channels length and facilitating proton diffusion, indicating the potential advantage of SCONs in application for proton exchange membranes (PEMs). In this study, Nafion-SCONs composite membranes were prepared by introducing SCONs into a Nafion membrane. The incorporation of SCONs not only improved proton conductivity, but also suppressed methanol permeability. This was due to the even distribution of ion channels, formed by strong electrostatic interaction between the well dispersed SCONs and Nafion polymer molecules. Notably, Nafion-SCONs-0.6 was the best choice of composite membranes. It exhibited enhanced performance, such as high conductivity and low methanol permeability. The direct methanol fuel cell (DMFC) with Nafion-SCONs-0.6 membrane also showed higher power density (118.2 mW cm⁻²), which was 44% higher than the cell comprised of Nafion membrane (81.9 mW cm⁻²) in 2 M methanol at 60 °C. These results enabled us to work on building composite membranes with enhanced properties, made from nanomaterials and polymer molecules.     

Magnetic field aligned nanocomposite proton exchange membranes based on sulfonated poly (ether sulfone) and Fe2O3 nanoparticles for direct methanol fuel cell application

Sulfonated poly (ether sulfone) (SP-ES) are prepared and optimized considering the transport properties and physicochemical stability. Afterward, nanocomposite membranes composed of SP-ES containing various loading weights of γ-Fe₂O₃ nanoparticles are fabricated. Nanoparticles assembled into an aligned form across the membrane by applying magnetic field during solvent casting. The effect of nanoparticles orientation is studied by consideration of the water uptake, membrane ionic conductivity, and activation energy as well as methanol permeability. Aligned membranes have a higher proton conductivity and also lower activation energy for proton migration as well as lower water uptake and methanol permeability. It is also noted that nanocomposite membranes have sufficient thermal stability and high electrochemical performance. Consequently, the anisotropic nanocomposite membranes with oriented nanoparticles demonstrate the ability to have potential application in fuel cells as well as ionic actuators.     

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.     

Simultaneously enhanced methanol barrier and proton conductive properties of phosphorylated titanate nanotubes embedded nanocomposite membranes

The current study aims at simultaneously enhancing the methanol barrier and proton conductive properties of membranes for direct methanol fuel cell (DMFC) by embedding phosphorylated titanate nanotubes (PTNTs) into chitosan (CS) membrane. The enhancement is most probably due to the intrinsic interfacial interactions between PTNTs and CS chains, which are verified by the increased thermal stability and homogeneous dispersion of the fillers. The influence of PTNTs incorporation conditions including acid concentration and filler content upon the resulting nanocomposite membrane performance is extensively investigated. Compared with plain CS membrane, the presence of PTNTs within chitosan matrix will lead to denser chain packing, thus reduce free volume cavity size and fractional free volume (FFV) according to positron annihilation lifetime spectroscopy analysis. The reduced FFV and more tortuous pathway significantly suppress the methanol crossover through the membranes. Meanwhile, the presence of PTNTs constructs an uninterrupted channel for proton migration via functionalized P–OH groups and adsorbed water, and therefore improving the proton conductivity substantially. As a result, the nanocomposite membranes exhibit desirable comprehensive performance, which is about ten times higher than that of Nafion 117. We envisage that the current observations hint the encouraging application promises of such nanocomposite membranes in DMFC.     

Poly(ethylene glycol) modified activated carbon for high performance proton exchange membrane fuel cells

A high water retention membrane is developed by co-assembling poly(ethylene glycol) (PEG) grafted activated carbon (AC-PEG) with Nafion. The AC-PEG is prepared via a sol–gel process. The use of PEG as a transporting medium in AC-PEG shows a largely improved water retention ability, a higher proton conductivity and a reduced swelling ratio, making it well suited for proton exchange membrane fuel cells (PEMFCs). Further, the composite membranes show improved mechanical properties at high temperature, thus ensuring the structural stability of membranes during the fuel cell operation. Compositional optimized AC-PEG/Nafion composite membrane (15 wt% compared to Nafion) demonstrates a better performance than the commercially available counterpart, Nafion 212, in fuel cell measurements. To identify the key factor of the improved performance, current interrupt technique is used to quantitatively verify the changes of resistance under different relative humidity environment.     

Improving the performance of sulfonated polymer membrane by using sulfonic acid functionalized hetero-metallic metal-organic framework for DMFC applications

Proton transport played a crucial part in the fuel cells, sensors, and batteries. The electrolyte used in fuel cells should possess high proton conductivity and good chemical stability. Herein, taking advantage of the high proton conductivity of metal-organic framework (MOF) and the good chemical stability of branched polymers, a new heterometallic mediated MOF (Zr-Cr-SO₃H) is synthesized and utilized as a filler in the highly branched sulfonated polymer (BSP). In addition, Zr-SO₃H MOF is also prepared for comparison. Transmission electron microscope study shows that the prepared MOF particles are spherical in size and interconnected through nanosheets. The optimized quantity of MOFs inside the polymer matrix improves the water sorption, mechanical property, and proton conductivity. The composite membranes display an improved open-circuit voltage than the pristine BSP membrane. By comparing the Zr-SO₃H MOF incorporated composite membrane, Zr-Cr-SO₃H MOF incorporated composite membranes display higher proton conductivity and peak power density in a single-cell test. In particular, the single-cell fabricated with Zr-Cr-SO₃H MOF incorporated composite membrane is able to reach the peak power density of 64.6 mWcm⁻² at 60°C, which is 26% greater than the Nafion 212 membrane. Furthermore, this work offers a new strategy for the utilization of hetero-metal MOF as a filler for proton exchange membrane applications.     

Chemical modification of Nafion membrane with 3,4-ethylenedioxythiophene for direct methanol fuel cell application

Nafion 117 membranes were modified by in situ chemical polymerization of 3,4-ethylenedioxythiophene using H₂O₂ as oxidant for direct methanol fuel cell application. Methanol permeability and proton conductivity of the poly(3,4-ethylenedioxythiophene)-modified Nafion membranes as a function of temperature were investigated. An Arrhenius-type dependency of methanol permeability and proton conductivity on temperature exists for all the modified membranes. Compared with Nafion 117 membrane at 60 °C, the methanol permeability of these modified membranes is reduced from 30% to 72%, while the proton conductivity is decreased from 4% to 58%, respectively. Because of low methanol permeability and adequate proton conductivity, the DMFC performances of these modified membranes were better than that of Nafion 117 membrane. A maximum power density of 48.4 mW cm⁻² was obtained for the modified membrane, while under same condition Nafion 117 membrane got 37 mW cm⁻².     

Polymer modified sulfonated PEEK ionomers membranes and the use of Ru3Pd6Pt as cathode catalyst for H2/O2 fuel cells

Nanocomposite membranes incorporating electrospun nanofibers of SPEEK, blended with 30 wt% PVB within a water-based matrix of SPEEK with 35 wt% PVA using water as solvent, were prepared and characterized for their application as Polymer Electrolyte Membrane Fuel Cells (PEMFCs) in H₂/O₂ operating at low temperatures. Compared with a dense bulk phase, an improvement of proton conductivity in the SPEEK-30PVB nanofiber framework was observed. The incorporation of the SPEEK-30PVB nanofibers provides mechanical improvement while the matrix phase of SPEEK-35PVA emphasizes the proton conductivity at crosslinking temperatures up to 140 °C. PEMFC performance tests showed promising results for the use of these novel low cost membranes. The nanocomposite membrane reached a power density which is 25% higher than that of Nafion117 membranes with MEAs constructed with Pt loading in anode and in cathode. However, when the Pt of the cathode is substituted by Ru₃Pd₆Pt, the power density is lower in Nafion117 MEAs than in the nanocomposite. When used commercial Pt-carbon cloth (Pt-ETEK) for the electrodes, the power density achieved is 1.4 times higher for the Nafion117 MEAs than SPEEK nanocomposites. The differences observed in performance is attributed to the large polarization losses found in the composite membranes because of the interfacial phenomena associated with the use of commercial Nafion-based electrodes.     

Amelioration of PEMFC performance at high temperature by incorporation of nanofiller (sepiolite/layered double hydroxide) in Nafion membrane

Nanoheterostructured material composed of sepiolite clay mineral in which is assembled a MgAl layered double hydroxide (LDH) was used in the preparation of Nafion composite electrolyte membranes and their behavior compared to those of membranes filled with the LDH alone. Both, the neat MgAl LDH and the MgAl LDH-sepiolite hybrid materials were obtained via the co-precipitation method. Sepiolite fibers provide a large external surface area for bonding MgAl LDH particles while maintaining high microporosity and water molecules. The nanocomposite membranes were prepared incorporating different amount of LDH or LDH-sepiolite hybrid. Composite membranes present better water retention, good thermal properties and high proton conductivities at high temperatures than the pure Nafion membrane. The proton conductivity at 100 °C and 100% RH reaches a value of 0.13 S/cm for the LDH-sepiolite Nafion membrane whereas is only 0.010 S/cm in the case of the Nafion membrane. Fuel cell tests using Nafion membranes containing LDH or LDH-sepiolite hybrid as composite electrolytes show a good result for the operation of the PEMFC at 80 °C, 100 °C and 110 °C, with a clear favoring effect of the LDH-sepiolite filler for operation at the highest temperatures.     

Understanding of temperature-dependent performance of short-side-chain perfluorosulfonic acid electrolyte and reinforced composite membrane

The short-side-chain (SSC) perfluorosulfonic acid (PFSA) membranes are important candidates as membrane electrolytes applied for high temperature or low relative humidity (RH) proton exchange membrane fuel cells. In this paper, the fuel cell performance, proton conductivity, proton mobility, and water vapor absorption of SSC PFSA electrolytes and the reinforced SSC PFSA/PTFE composite membrane are investigated with respect to temperature. The pristine SSC PFSA membrane and reinforced SSC composite membrane show better fuel cell performance and proton conductivity, especially at high temperature and low relative humidity conditions, compared to the long-side-chain (LSC) Nafion membrane. Under the same condition, the proton mobility of SSC PFSA membranes is lower than that of the LSC PFSA membrane. The water vapor uptake values for Nafion 211 membrane, pristine SSC PFSA membrane and SSC PFSA/PTFE composite membrane are 9.62, 11.13, and 11.53 respectively at 40 °C and they increase to 9.89, 12.55 and 13.09 respectively at 120 °C. The high water content of SSC PFSA membrane makes it maintain high performance even at elevated temperatures.     

Polymer electrolyte membranes containing titanate nanotubes for elevated temperature fuel cells under low relative humidity

Nafion-titanate nanotubes composite membranes prepared through casting process have been investigated as electrolytes for polymer electrolyte membrane fuel cell applications under low relative humidity. The glass transition temperature and the decomposition temperature of composite membrane at dry state are higher than those of pristine Nafion membrane. Cracks have been observed in the membrane at the concentration of nanotubes above 5 wt.%. The maximum proton conductivity at 100 °C and 50% relative humidity is observed with the concentration of doped titanate nanotubes of 5 wt.%. Solid nuclear magnetic resonance spectrum is applied to qualitatively characterize the status of water inside the membrane at different temperatures. The power densities at 0.8 V for cell assembled from composite membrane containing 5 wt.% of titanate nanotubes are about 13% and 35% higher than that for plain Nafion cells under 50% relative humidity at 65 °C and 90 °C, respectively.     

Nafion/polyaniline composite membranes specifically designed to allow proton exchange membrane fuel cells operation at low humidity

A Nafion and polyaniline composite membrane (designated Nafion/PANI) was fabricated using an in situ chemical polymerization method. The composite membrane showed a proton conductivity that was superior to that obtained with Nafion^® 112 at low humidity (e.g. RH = 60%). Water uptake measurements revealed similarities between the Nafion^® 112 and Nafion/PANI membranes at different humidities. The high conductivity of the Nafion/PANI membrane at low humidity is hypothesized to be due to the existence of the extended conjugated bonds in the polyaniline; proton transfer is facilitated via the conjugated bonds in lower humidity environments allowing retention of the relatively high conductivity. Correspondingly, the performance of a single cell fuel cell containing the Nafion/PANI composite membrane is improved compared to a Nafion^® 112-containing cell under low humidity conditions. This is important for portable fuel cells, which are required to operate without external humidification.     

Phosphonic acid-grafted mesostructured silica/Nafion hybrid membranes for fuel cell applications

Highly conductive and hydration retentive mesoporous silica/Nafion and organically modified mesoporous silica/Nafion membranes are prepared by a surfactant templated sol-gel process involving Nafion solution and silica precursors. Spectroscopic analyses reveal that the in situ generation of a well-condensed silica network and organic (-PO₃H₂) functionalization of the inorganic segment are effectively achieved in the prepared membranes. The homogeneous dispersion of silica nanoparticles in the polymer matrix is apparent in electron micrographs. Structural analyses using small-angle X-ray scattering confirms the periodic short range structural order associated with these mesostructured hybrid membranes. These hybrid membranes exhibit an increased water uptake and an associated conductivity enhancement at 100% RH, compared to unmodified Nafion. More significantly, the functionalized silica/Nafion membranes show high proton conductivities at 80 °C and 50% RH, which is more than 6 times higher than that of Nafion. Thermogravimetric analysis, low temperature DSC studies and a comparison of activation energies (E_a) obtained from temperature-dependent conductivity plots of the membranes at different humidities, provide evidence for the better retention of water in the hybrid membranes compared to Nafion; thereby demonstrating the promising potential of these membranes to tolerate the variations in humidity at elevated temperatures.