Self-humidifying Composite Membrane Research Articles

Preparation of new self-humidifying composite membrane by incorporating graphene and phosphotungstic acid into sulfonated poly(ether ether ketone) film

In this work, a combination of constituent materials capable of improving the moisture retention and proton conductivity (PC) was incorporated into sulfonated poly (ether ether ketone) (SPEEK) membranes in order to prepare new, self-humidifying composite membranes (SHMs) for proton exchange membrane fuel cells. The property-improving components were incorporated into the cast SPEEK film in an appropriate microstructural architecture to prepare the SHMs with increased water retention and PC. SHMs were therefore prepared with the inclusion of carboxyl-functionalized graphene (G(c)) and phosphotungstic acid (PWA) with varying proportions into the SPEEK film. The structure of the SPEEK/G(c)/PWA composite membranes was characterized by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, energy dispersive X-ray analysis, thermogravimetric analysis and X-ray photoelectron spectroscopy. The physicochemical properties of the composite membranes, such as ion exchange capacity, water uptake, thermal stability and PC, were investigated. This work provides confirmation that self-humidifying properties are improved at temperature above 60 °C through a combinational inclusion of G(c) and PWA within SPEEK and the new self-humidifying membranes have potential for use in medium temperature direct methanol fuel cells.

Effect of sulfonated carbon nanofiber-supported Pt on performance of Nafion ®-based self-humidifying composite membrane for proton exchange membrane fuel cell

In the present study, the Nafion ®-based self-humidifying composite membrane (N-SHCM) with sulfonated carbon nanofiber-supported Pt ( s-Pt/CNF) catalyst, N- s-Pt/CNF, is successfully prepared using the solution-casting method. The scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS) images of N- s-Pt/CNF indicate that s-Pt/CNF is well dispersed in the Nafion ® matrix due to the good compatibility between Nafion ® and s-Pt/CNF. Compared with those of the non-sulfonated Pt/CNF-containing N-SHCM, N-Pt/CNF, the properties of N- s-Pt/CNF, including electronic resistivity, ion-exchange capacity (IEC), water uptake, dimensional stability, and catalytic activity, significantly increase. The maximum power density of the proton exchange membrane fuel cell (PEMFC) fabricated with N- s-Pt/CNF operated at 50 °C under dry H 2/O 2 condition is about 921 mW cm −2, which is approximately 34% higher than that with N-Pt/CNF.

Reinforced and self-humidifying composite membrane for fuel cell applications

A novel preparation method for a composite proton exchange membrane with reinforced strength and self-humidifying property was developed. Using self-assembly method, highly dispersed poly(diallyldimethylammonium chloride) (PDDA) stabilized Pt nanoparticles were mounted onto the pores of poly(tetrafluoroethylene) (PTFE) porous film to serve the self-humidifying purpose. With Pt nanoparticles fixed on the PTFE pores, the potential problem of any short circuit because of the use of metal nanoparticles can be prevented. Pt-PDDA/PTFE substrate in the composite membrane can enhance the mechanical strength of the membrane and distribute self-humidifying layer adjacent to the anode side. Compared with the cells fabricated with conventional Nafion ® and PTFE/Nafion membranes, the performance of the cells with this composite membrane is dramatically improved under dry conditions. Electrochemical impedance spectroscopy technique revealed that these self-humidifying composite membranes could minimize membrane conductivity loss under dry conditions.

Fabrication and investigation of SiO 2 supported sulfated zirconia/Nafion ® self-humidifying membrane for proton exchange membrane fuel cell applications

A self-humidifying composite membrane based on Nafion ® hybrid with SiO 2 supported sulfated zirconia particles (SiO 2–SZ) was fabricated and investigated for fuel cell applications. The bi-functional SiO 2–SZ particles, possessing hygroscopic property and high proton conductivity, were homemade and as the additive incorporated into our composite membrane. X-ray diffraction (XRD) and Fourier infrared spectrum (FT-IR) techniques were employed to characterize the structure of SiO 2–SZ particles. Scanning electronic microscopy (SEM) and energy dispersive spectroscopy (EDS) measurements were conducted to study the morphology of composite membrane. To verify the advantages of Nafion ®/SiO 2–SZ composite membrane, the IEC value, water uptake, proton conductivity, single cell performance and areal resistance were compared with Nafion ®/SiO 2 membrane and recast Nafion ® membrane. The single cell employing our Nafion ®/SiO 2–SZ membrane exhibited the highest peak power density of 0.98 W cm −2 under dry operation condition in comparison with 0.74 W cm −2 of Nafion ®/SiO 2 membrane and 0.64 W cm −2 of recast Nafion ® membrane, respectively. The improved performance was attributed to the introduction of SiO 2–SZ particles, whose high proton conductivity and good water adsorbing/retaining function under dry operation condition, could facilitate proton transfer and water balance in the membrane.

An inorganic/organic self-humidifying composite membranes for proton exchange membrane fuel cell application

With an aim to operate the proton exchange membrane fuel cells (PEMFCs) with dry reactants, an inorganic/organic self-humidifying membrane based on sulfonated polyether ether ketone (SPEEK) hybrid with Cs 2.5H 0.5PW 12O 40 supported Pt catalyst (Pt-Cs2.5 catalyst) has been investigated. The Pt-Cs2.5 catalysts incorporated in the SPEEK matrix provide the site for catalytic recombination of permeable H 2 and O 2 to form water, and meanwhile avoid short circuit through the whole membrane due to the insulated property of Cs 2.5H 0.5PW 12O 40 support. Furthermore, the Pt-Cs2.5 catalyst can adsorb the water and transfer proton inside the membrane for its hygroscopic and proton-conductive properties. The structure of the SPEEK/Pt-Cs2.5 composite membrane was characterized by XRD, FT-IR, SEM and EDS. Comparison of the physicochemical and electrochemical properties, such as ion exchange capacity (IEC), water uptake and proton conductivity between the plain SPEEK and SPEEK/Pt-Cs2.5 composite membrane were investigated. Additive stability measurements indicated that the Pt-Cs2.5 catalyst showed improved stability in the SPEEK matrix compared to the PTA particle in the SPEEK matrix. Single cell tests employing the SPEEK/Pt-Cs2.5 self-humidifying membrane and the plain SPEEK membrane under wet or dry operation conditions and primary 100 h fuel cell stability measurement were also conducted in the present study.

Progress on the Composite Membranes for PEM Fuel Cells

In this paper, R & D on the reinforced and self-humidifying composite membranes for proton exchange membrane fuel cells (PEMFCs) in our group is presented. It is shown that both the reinforced and self-humidifying membrane have attained an enhanced performance.

Novel-SiO<sub>2</sub>-Doped Proton Exchange Membrane for Self-Humidifying Fuel Cell

To retain the optimum hydration level of the proton exchange membrane fuel cell (PEMFC) without humidification sub-system, a novel self-humidifying composite membrane was fabricated by the technology of Si[OCH2CH3]4 in situ sol-gel reaction in a commercial Nafion 112 membrane. The physico-chemical properties of the membrane were studied by means of AFM, SEM and AC impedance. These results showed that the nano-SiO2 reactant was uniformly distributed in the composite membrane. It was found that the proton conductivity increased observably by dispersing 3 wt % nano-SiO2 in the composite membrane at low water content, and the SiO2/Nafion composite membrane improved the self-humidifying performance of PEMFC.

Cs 2.5H 0.5PWO 40/SiO 2 as addition self-humidifying composite membrane for proton exchange membrane fuel cells

In this paper, we first reported a novel self-humidifying composite membrane for the proton exchange membrane fuel cell (PEMFC). Cs 2.5H 0.5PWO 40/SiO 2 catalyst particles were dispersed uniformly into the Nafion ® resin, and then Cs 2.5H 0.5PWO 40–SiO 2/Nafion composite membrane was prepared using solution-cast method. Compared with the H 3PWO 40 (PTA) , the Cs 2.5H 0.5PWO 40/SiO 2 was steady due to the substitute of H + with Cs + and the interaction between the Cs 2.5H 0.5PWO 40 and SiO 2. And compared with the performance of the fuel cell with commercial Nafion ® NRE-212 membrane, the cell performance with the self-humidifying composite membrane was obviously improved under both humidified and dry conditions at 60 and 80 °C. The best performance under dry condition was obtained at 60 °C. The self-humidifying composite membrane could minimize membrane conductivity loss under dry conditions due to the presence of catalyst and hydrophilic Cs 2.5H 0.5PWO 40/SiO 2 particles.

Pt/CNTs-Nafion reinforced and self-humidifying composite membrane for PEMFC applications

A novel thin three-layer reinforced and self-humidifying composite membrane has been developed for PEMFCs. The membrane has two outer layers of plain Nafion and a middle layer of Pt/carbon nanotubes (Pt/CNTs) dispersed Nafion. The Pt/CNTs present in the membrane provides the sites for the catalytic recombination of H 2 and O 2 permeating through the membrane from the anode and cathode to produce water and improve the mechanical properties of the composite membrane at the same time. The water produced directly humidifies the membrane and allows the operation of PEMFCs with dry reactants. The electrochemical performance and mechanical properties of the composite membranes are compared with those of a commercial Nafion ® membrane. The self-humidifying composite membrane could minimize membrane conductivity loss under dry conditions and improve mechanical strength due to the presence of the Pt/CNTs.

A Self-Humidifying Composite Membrane with Self-Assembled Pt Nanoparticles for Polymer Electrolyte Membrane Fuel Cells

A method for preparing a self-humidifying composite membrane for the polymer electrolyte membrane fuel cells (PEMFCs) is presented. In this method, perfluorosulfonylfluroride resin is impregnated into a PTFE porous support and positively charged poly(diallymethylammonium)-Pt nanoparticles are self-assembled into the composite membrane to form a self-humidifying layer. The self-assembled Pt nanoparticles were dispersed uniformly in the composite membrane and serve as the catalytic center for the combination reaction between the crossover hydrogen and oxygen, effectively self-humidifying the membrane. The self-assembly of Pt nanoparticles has little adverse effect on the proton conductivity of the composite membrane. The composite membrane with self-assembled Pt nanoparticles improves significantly the performance of PEMFCs as compared to that of the composite membrane without self-assembled Pt nanoparticles. The results show that optimum loading of the self-assembled Pt nanoparticle is about under conditions of the present study.

An Ultrathin Self-Humidifying Membrane for PEM Fuel Cell Application: Fabrication, Characterization, and Experimental Analysis

An ultrathin poly(tetrafluoroethylene) (PTFE)-reinforced multilayer self-humidifying composite membrane (20 microm, thick) is developed. The membrane is composed of Nafion-impregnated porous PTFE composite as the central layer, and SiO2 supported nanosized Pt particles (Pt-SiO2) imbedded into the Nafion as the two side layers. The proton exchange membrane (PEM) fuel cell employing the self-humidifying membrane (Pt-SiO2/NP) turns out a peak power density of 1.40 W cm(-2) and an open circuit voltage (OCV) of 1.032 V under dry H2/O2 condition. The excellent performance is attributed to the combined result of both the accelerated water back-diffusion in the thin membrane and the adsorbing/releasing water properties of the Pt-SiO2 catalyst in the side layers. Moreover, the inclusion of the hygroscopic Pt-SiO2 catalyst inside the membrane results in an enhanced anode self-humidification capability and also the decreased cathode polarization (accordingly an improved cell OCV). Several techniques, such as transmission electronic microscopy, scanning electronic microscopy, energy dispersive spectroscopy, thermal analysis and electrochemical impedance spectroscopy etc., are employed to characterize the Pt-SiO2/NP membrane. The results are discussed in comparison with the plain Nafion/PTFE membrane (NP). It is established that the reverse net water drag (from the cathode to the anode) across the Pt-SiO2/NP membrane reaches 0.16 H2O/H+. This implies a good hydration of the Pt-SiO2/NP membrane and thus ensures an excellent PEM fuel cell performance under self-humidification operation.

Pt/SiO 2 catalyst as an addition to Nafion/PTFE self-humidifying composite membrane

A novel self-humidifying reinforced composite membrane for the proton exchange membrane fuel cell (PEMFC) was developed. Pt/SiO 2 catalyst particles were dispersed uniformly into the Nafion resin, and then Pt–SiO 2/Nafion/PTFE reinforced composite membrane was prepared using solution-cast method. Compared with the performance of the fuel cell with commercial Nafion ® NRE-212 membrane, the cell performance with the self-humidifying composite membrane was obviously improved under both humidified and dry conditions at 80–120 °C. The self-humidifying composite membrane could minimize membrane conductivity loss under dry conditions due to the presence of catalyst and hydrophilic Pt/SiO 2 particles.

Self-Humidifying Cs2.5H0.5PW12O40 / Nafion / PTFE Composite Membrane for Proton Exchange Membrane Fuel Cells

A Cs2.5H0.5PW12O40/Nafion/polytetrafluoroethylene (PTFE) self-humidifying composite membrane was developed for proton exchange membrane fuel cells. It was prepared by recasting the Cs2.5H0.5PW12O40/Nafion self-humidifying layer onto the two sides of a Nafion/PTFE composite membrane with a solution-recast method. Due to the strong acidic, hydrophilic, and redox properties of Cs2.5H0.5PW12O40, the Cs2.5H0.5PW12O40/Nafion self-humidifying layer not only contributes to humidify the membrane but also contributes to the improvement of the open-circuit voltage of the fuel cell. When the self-humidifying composite membrane was employed as an electrolyte in H-2/O-2 PEMFC, a higher maximum power density value (1.1 W/cm(2)) was obtained than that of Nafion/PTFE composite membrane (0.6 W/cm(2)), under the operating conditions of 70 degrees C and at the humidified temperature of 20 degrees C. (c) 2005 The Electrochemical Society.

A Novel PTFE-Reinforced Multilayer Self-Humidifying Composite Membrane for PEM Fuel Cells

A novel polytetrafluoroethylene (PTFE)-reinforced multilayer self-humidifying composite membrane is developed. The membrane is composed of Nafion-impregnated porous PTFE composite as the central layer and nanosized SiO2 supported Pt catalyst imbedded into Nafion as the two side layers. The proton exchange membrane (PEM) fuel cells employing the self-humidifying membrane (20 mu m thick) under dry H-2/O-2 gave a peak power density of 0.95 W/cm(2) and an open-circuit voltage of 1.032 V. The good membrane performance is attributed to hygroscopic Pt-SiO2 catalyst at the two side layers, which results in enhanced anode side self-humidification function and decreased cathode polarization. (c) 2005 The Electrochemical Society.

Pt-C/SPEEK/PTFE Self-Humidifying Composite Membrane for Fuel Cells

A Pt-C/sulfonated poly~ether ether ketone!/polytetrafluoroethylene ~Pt-C/SPEEK/PTFE! self-humidifying composite membrane for the H2 /O2 fuel cell was developed. Compared with the performance of the cells prepared with SPEEK/PTFE composite membranes, the performance with the self-humidifying composite membranes was appreciably improved when holding the humidity of cathode gas constant. The Pt-C/SPEEK/PTFE composite membrane can supply water to the anode electrode side

Development of novel self-humidifying composite membranes for fuel cells

A novel preparation method for self-humidifying membranes of proton exchange membrane fuel cells (PEMFCs) was developed. Using solution-cast method, PTFE porous substrates in these composite membranes can increase their strength and distribute self-humidifying layers adjacent to the anode side. Compared with the cells fabricated with ordinary membranes, the performance of the cells with these self-humidifying proton exchange membranes (PEMs) are dramatically improved in both cell voltage and the current density under dry conditions, and the cell using the Pt/C-PEM shows the best and most stable performance. EIS technique revealed that these self-humidifying composite membranes could minimize membrane conductivity loss under dry conditions.