Porous zirconium oxide nanotube modified Nafion composite membrane for polymer electrolyte membrane fuel cells operated under dry conditions (original) (raw)
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ACS Applied Materials & Interfaces, 2014
We describe a facile route to fabricate mesoporous metal oxide (TiO 2 , CeO 2 and ZrO 1.95) nanotubes for efficient water retention and migration in a Nafion membrane operated in polymer electrolyte fuel cell under low relative humidity (RH). Porous TiO 2 nanotubes (TNT), CeO 2 nanotubes (CeNT), and ZrO 1.95 (ZrNT) were synthesized by calcining electrospun polyacrylonitrile nanofibers embedded with metal precursors. The nanofibers were prepared using a conventional single spinneret electrospinning technique under an ambient atmosphere. Their porous tubular morphology was observed by SEM and TEM analyses. HR-TEM results revealed a porous metal oxide wall composed of small particles joined together. The mesoporous structure of the samples was analyzed using BET. The tubular morphology and outstanding water absorption ability of the TNT, CeNT, and ZrNT fillers resulted in the effective enhancement of proton conductivity of Nafion composite membranes under both fully humid and dry conditions. Compared to a commercial membrane (Nafion, NRE-212) operated under 100% RH at 80°C, the Nafion−TNT composite membrane delivered approximately 1.29 times higher current density at 0.6 V. Compared to the Nafion-TiO 2 nanoparticles membrane, the Nafion−TNT membrane also generated higher current density at 0.6 V. Additionally, compared to a NRE-212 membrane operated under 50% RH at 80°C, the Nafion−TNT composite membrane exhibited 3.48 times higher current density at 0.6 V. Under dry conditions (18% RH at 80°C), the Nafion−TNT, Nafion-CeNT, and Nafion-ZrNT composite membranes exhibited 3.4, 2.4, and 2.9 times higher maximum power density, respectively, than the NRE-212 membrane. The remarkably high performance of the Nafion composite membrane was mainly attributed to the reduction of ohmic resistance by the mesoporous hygroscopic metal oxide nanotubes, which can retain water and effectively enhance water diffusion through the membrane.
Properties and fuel cell performance of a Nafion-based, sulfated zirconia-added, composite membrane
Journal of Power Sources, 2008
The effect of an acidic inorganic additive, i.e. sulfated zirconia, on Nafion-based polymer electrolytes is evaluated by comparing the properties in terms of conductivity and fuel cell performance of a composite sulfated zirconia-added Nafion membrane with those of an additive-free Nafion membrane. The peculiar surface properties of the selected filler promote a higher hydration level and a higher conductivity for the composite membrane under unsaturated conditions, i.e. at 20% RH. Tests on H 2-air fully humidified cells, monitored at 70 • C and at atmospheric pressure, reveal small differences when passing from a plain Nafion to a composite Nafion/sulfated zirconia membrane as electrolyte. However, remarkably great improvements are observed for the composite membrane-based cell when the comparison tests are run at low relative humidity and high temperature, this outlining the beneficial role of the sulfated zirconia additive.
Zirconia Based / Nafion Nanocomposite Membranes for Fuel Cell Applications
2014
The nanoparticles of zirconium oxide, sulfated zirconia and phosphated zirconia were used to modify Nafion membrane in order to improve the water retention, thermal stability, proton conductivity and methanol permeability. The modified Nafion nanocomposite membranes were used for high temperature fuel cell between 120-140°C. The inorganic nanoparticles were incorporated within Nafion by recast, swelling-impregnation and ion exchange methods. The inorganic nanoparticles were characterized by XRD, BET, FTIR, TGA, DSC, SEM and TEM, while nanocomposite membranes were characterized for water uptake, ion exchange capacity, methanol permeability, and proton conductivity. Pristine ZrO2, sulfated and phosphated ZrO2 were successfully synthesized. The particle sizes ranged from 10 nm to 30 nm, with good dispersity in the membrane. The conductivity of the Nafion / 5% sulfated zirconia membrane exceeded 0.103 S/cm at room temperature and has the highest water uptake of 35%. On the other hand, N...
Journal of Power Sources, 2006
Recast Nafion composite membranes containing three different percentages (5%, 10% and 20%, w/w) of commercial Zirconium(IV) oxide as an inorganic filler were developed by the Doctor-Blade casting technique in order to work in direct hydrogen polymer electrolyte fuel cells (DH-PEFCs) in critical operative conditions for the fuel cell at a temperature of about 120-130 • C. By mixing a 10% (w/w) Nafion-dimethylacetammide (DMAc) dispersion with the inorganic compound, composite membranes were prepared. The developed membranes were characterised by water retention capacity (Wup%), ion exchange capacity (IEC, meq g −1), thermo-gravimetric analysis and by X-ray measurements. From XRD measurements, the ZrO 2 powder insertion was confirmed; the introduced amount was verified by TG analysis that highlighted the major thermal resistance of the developed membranes. Moreover, the chemical-physical results showed an increase of the water uptake and a decrease of the IEC with the increase of inorganic compound percentage. The introduction of the inorganic powder improved the mechanical characteristics of the developed composite membranes. Moreover, the membranes were tested in a 5 cm 2 commercial single cell from 80 • C to 130 • C in humidified H 2 /air with pressures of 3.0 abs. bar and the obtained results compared to a bare Nafion recast membrane (N16) developed through the same method and used as a reference. Power density values of 604 mW cm −2 and of 387 mW cm −2 were obtained at 0.6 V and at T = 110 • C (100% of relative humidity) and T = 130 • C (85% RH), respectively, for the composite ZrO 2-Nafion membrane containing 10% (w/w) of inorganic filler.
Materials Science for Energy Technologies, 2018
In this work, Nafion ionomer was prepared by a dissolution method in high pressuretemperature autoclave reactor using Nafion membrane sources. Zirconia nanoparticles were synthesized by the microwave assisted gel combustion method. The synthesized nanoparticles were characterized by XRD and FESEM, and then added to the Nafion solution to prepare recast Nafion nanocomposite membranes (R-Nafion/ZrO 2) with different loading of ZrO 2 nanoparticles. Membranes were prepared by recasting method and characterized in terms of water uptake, dimensional stability, ionic conductivity, chemical stability (Fenton test), tensile strength, and scanning electron microscope (SEM) techniques. The obtained results for nanocomposite membranes were compared to the filler-free recast Nafion and commercial Nafion membranes. The nanocomposite membranes showed higher water uptake, mechanical and oxidative stabilities and the hygroscopic zirconia nanoparticles resulted higher proton conductivity of nanocomposite membranes at different temperatures in comparison with pure recast Nafion membrane. The prepared membranes showed defect free, dense microstructure, and good dispersion of nanoparticles in the membranes' matrix. The results illustrated the prepared nanocomposite membranes have good physicochemical and electrochemical properties for PEMFC applications.
Journal of Membrane Science, 2015
High performance and durable electrolyte membrane operated in polymer electrolyte membrane fuel cells (PEMFCs) under low relative humidity (RH) has been achieved by incorporating various diameter sizes of mesoporous hygroscopic TiO 2 nanotubes (TNT) in a perfluorosulfonic acid (Nafion s) membrane. Porous TNTs with different tube diameters are synthesized by thermal annealing the electrospun polymer containing titanium precursor mat at 600°C under an air atmosphere. The diameter of the TNT is significantly controlled by changing the concentration of the precursor solution. Compared to a commercial membrane (Nafion, NRE-212), the Nafion-TNT-10 composite membrane operated under 100% RH at 80°C generates about 1.3 times higher current density at 0.6 V, and 3.4 times higher maximum power density operated under dry conditions (18% RH at 80°C). In addition, the Nafion-TNT-10 composite membrane also exhibits stable and durable operation under dry conditions. The remarkably high performance of the Nafion-TNT-10 composite membrane is mainly attributed to the significant reduction of the ohmic resistance as well as the improvement of cathode catalyst utilization by incorporating TNTs, which greatly enhances the water retention and the water management capability through the membrane. Furthermore, Nafion-TNT membranes exhibit superior mechanical property.
Journal of Power Sources, 2002
Composite polymer electrolyte membranes were prepared by impregnating Nafion solution into the porous expanded PTFE (ePTFE) films as a substrate and their single cell performance, gas permeability, water flux, and water uptake were investigated. Although the nitrogen permeability of the composite membrane was higher than that of Nafion 112, there was not the serious cross-over of gases to diminish cell performance and it was seen that the cell performance could be improved by reduced thickness of the composite membrane. It was also seen that water uptake and water flux of the composite membrane were dependent on the Nafion loading amount on the substrate and, therefore, the thickness of the membrane. The water uptake as well as the water flux of the composite membrane increased as the Nafion loading amount increased and the increase rate of water uptake with temperature for the composite membranes was found to be larger than Nafion 112. #
Journal of Power Sources, 2007
A novel Pt/zeolite-Nafion (PZN) polymer electrolyte composite membrane is fabricated for self-humidifying polymer electrolyte membrane fuel cells (PEMFCs). A uniform dispersion of Pt nanoparticles with an average size of 3 nm is achieved by ion-exchange of the zeolite HY. The Pt nanoparticles embedded in the membrane provide the catalytic sites for water generation, whereas the zeolite HY-supported Pt particles absorbs water and make it available for humidification during cell operation at elevated temperature. Compared with the performance of ordinary membranes, the performance of cells with PZN membranes is improved significantly under dry conditions. With dry H 2 and O 2 at 50 • C, the PZN membrane with 0.65 wt.% of Pt/zeolite (0.03 mg Pt cm −2) gives 75% of the performance obtained at 0.6 V with the humidified reactants at 75 • C. Impedance analysis reveales that an increase in charge-transfer resistance is mainly responsible for the cell performance loss operated with dry gases.
Journal of Membrane Science, 2004
The physio-chemical properties of Nafion 115 and a composite Nafion 115/Zirconium Phosphate (25wt%) membranes are compared. The composite membrane takes up more water than Nafion at the same water activity. However, the proton conductivity of the composite membrane is slightly less than that for Nafion 115. Small angle X-ray scattering shows the hydrophilic phase domains in the composite membrane are spaced further apart than in Nafion 115, and the composite membrane shows less restructuring with water uptake. Despite the lower proton conductivity of the composite membranes they display better fuel cell performance than Nafion 115 when the fuel cell is operated under-humidified. It is suggested that the composite membrane has a greater rigidity that accounts for its improved fuel cell performance.