Anchoring Water Soluble Phosphotungstic Acid by Hybrid Fillers to Construct Three-Dimensional Proton Transport Networks

Phosphotungstic acid (HPW)-filled composite proton exchange membranes possess high proton conductivity under low relative humidity (RH). However, the leaching of HPW limits their wide application. Herein, we propose a novel approach for anchoring water soluble phosphotungstic acid (HPW) by polydopamine (PDA) coated graphene oxide and halloysite nanotubes (DGO and DHNTs) in order to construct hybrid three-dimensional proton transport networks in a sulfonated poly(ether ether ketone) (SPEEK) membrane. The introduction of PDA on the surfaces of the hybrid fillers could provide hydroxyl groups and secondary amine groups to anchor HPW, resulting in the uniform dispersion of HPW in the SPEEK matrix. The SPEEK/DGO/DHNTs/HPW (90/5/5/60) composite membrane exhibited higher water uptake and much better conductivity than the SPEEK membrane at low relative humidity. The best conductivity reached wass 0.062 S cm−1 for the composite membrane, which is quite stable during the water immersion test.

Novel proton conducting core–shell PAMPS-PVBS@Fe2TiO5 nanoparticles as a reinforcement for SPEEK based membranes

In this study, new nanocomposite membranes from sulfonated poly (ether ether ketone) (SPEEK) and proton-conducting Fe2TiO5 nanoparticles are prepared by the solution casting method. Sulfonated core–shell Fe2TiO5 nanoparticles are synthesized by redox polymerization. Therefore, 4-Vinyl benzene sulfonate (VBS) and 2-acrylamide-2-methyl-1-propane sulfonic acid (AMPS) are grafted on the surface of nanoparticles through radical polymerization. The different amounts of hybrid nanoparticles (PAMPS@Fe2TiO5 and PVBS@Fe2TiO5) are incorporated into the SPEEK matrix. The results show higher proton conductivity for all prepared nanocomposites than that of the SPEEK membrane. Embedding the sulfonated Fe2TiO5 nanoparticles into the SPEEK membrane improves proton conductivity by creating the new proton conducting sites. Besides, the nanocomposite membranes showed improved mechanical and dimensional stability in comparison with that of the SPEEK membrane. Also, the membranes including 2 wt% of PAMPS@Fe2TiO5 and PVBS@Fe2TiO5 nanoparticles indicate the maximum power density of 247 mW cm−2 and 226 mW cm−2 at 80 °C, respectively, which is higher than that of for the pristine membrane. Our prepared membranes have the potential for application in polymer electrolyte fuel cells.

A promising Al-CeZrO4/HPW-incorporated SPEEK composite membrane with improved proton conductivity and chemical stability for PEM fuel cells

An improved sulfonated poly (ether ether ketone) (SPEEK) nanocomposite membrane was prepared by incorporating both phosphotungstic acid (HPW) and Al doped cerium-based oxides (Al-CeZrO4) in SPEEK matrix. The HPW was immobilized by Al-CeZrO4 so that firmly dispersed acid–base pairs were formed. The introduction of Al-CeZrO4 helped improve the chemical stability of the pristine (baseline) SPEEK membrane without compromising the conductivity, and the addition of HPW further enhanced the conduction of protons through acid–base interactions. Stability tests showed that when the SPEEK/Al-CeZrO4 nanocomposite membrane was immersed in a Fenton’s solution for 108 h at 80°C, a loss of 34.9% in proton conductivity was observed, which is 24.1% less than that of the pristine SPEEK membrane, indicating that the attenuation of membrane proton conductivity was inhibited. At the same time, the proton conductivity of the SPEEK/Al-CeZrO4/HPW nanocomposite membrane (that has already incorporated HPW) was increased by 15.5% compared to the SPEEK/Al-CeZrO4 nanocomposite membrane. Hence, Al-CeZrO4/HPW is considered as an effective inorganic nanofiller for improving both proton conductivity and chemical stability of SPEEK membranes, and the hybrid composite membrane is worth further studying.

Modelling IR Spectra of Sulfonated Polyether Ether Ketone (SPEEK) Membranes for Fuel Cells

SPEEK (sulfonated polyether ether ketone) membranes have been prepared and characterized. The SPEEK membrane geometry and theoretical vibration spectra calculated using density functional theory (DFT) as depending from membrane chain length and polymer cross-linking. Analyzed the limitations of the method by comparing theoretical and experimental IR spectra.

ELECTROSPUN STRONTIUM CROSS-LINKED SULFONATED POLY (ETHER ETHER KETONE) SPEEK NANOFIBER FOR PROTON EXCHANGE MEMBRANE FUEL CELL

Strontium (Sr) cross-linked nanofibrous membranes of sulfonated polyether ether ketone (SPEEK) were successfully prepared using the electrospinning technique. Metal-polymer physical cross-linked has been proposed as a way to improve the mechanical and chemical stabilities of the electrospun SPEEK membrane which we found in this finding can help to reduced water uptake compared with the non-crosslinked membrane. Physical cross-linked of Sr-SPEEK membranes were fabricated by immersion process which were than electrospun into nanofibrous membranes. The morphologies of electrospun Sr-SPEEK membrane, fabricated under different concentrations of Sr were presented which show up to 6% concentration of Strontium was able to be electrospun. On the electrical properties of the electrospun membrane, conductivity for the sample with 6% Sr weight percentage has given 0.188 S/cm which is about 80% higher than the film cast Nafion-117 at 80˚C as cited before. This particular result is a hallmark of the studies as it shows that a combination of nanostructured with crosslink is proven to work in favor of producing proton exchange membrane fuel cell (PEMFC) which performed much better than Nafion based membrane.

High degree sulfonated poly(ether ether ketone) blend with polyvinylidene fluoride as a potential proton-conducting membrane fuel cell

Sulfonated poly(ether ether ketone) (sPEEK) membrane is a promising proton-conducting membrane for fuel cell. However, the performance and lifetime of sPEEK membrane depend on the degree of sulfonation (DS). High DS of sPEEK increases the performance, but the mechanical properties could deteriorate progressively which affect its lifetime. Thus, this study investigated the effect of adding polyvinylidene fluoride (PVDF) into high DS (80%) of sPEEK through solution blending method toward its physicochemical properties and morphology structures. The PVDF concentration was varied to 5, 10, 15, and 20 wt% relative to the sPEEK content. The existence of hydrophobic PVDF in 80% sPEEK improved the mechanical properties where the water uptake and swelling degree of membrane decreased, whereas the tensile strength increased. The sPEEK/PVDF 15 exhibited the highest proton conductivity (46.23 mS cm−1) at 80°C. Incorporating PVDF into high DS of sPEEK enhanced the mechanical properties which can be used as a proton-conducting membrane for fuel cell that may improve the performance and prolong the lifetime of the cell.

The Effects of Sulfonated Graphene Oxides (sGO) on Ion Conductivity and Permeability of the Vanadium Redox Flow Batteries Membranes Based on Sulfonated Poly(Ether Ether Ketone) Composite

Sulfonated graphene oxide (sGO) was used as a filler to enhance performance of sulfonated poly(ether ether ketone)(sPEEK) membrane. The sGO was firstly prepared by treating graphene oxides (GO) with sulfanilic acid at 70 °C for 20 h. The sGO was characterized by FTIR and XPS techniques. Composite membranes of various amount of sGO were fabricated via solution casting method. The properties of composite membranes were investigated by measuring ion exchange capacity (IEC), water uptake, ion conductivity and vanadium ion permeability. From the results, it was found that the IEC and water uptake of the membranes increased after adding the sGO. Ion conductivity of the sPEEK membrane also increased from 8.94*10-3 Scm-1 to 10.55*10-3 Scm-1. Moreover, permeability of vanadyl sulfate (VOSO4) through the composite membranes were decreased. These composite membranes exhibit great potential for vanadium redox flow batteries application.

Novel sulfonated poly(ether ether ketone)/triphenylamine hybrid membrane for vanadium redox flow battery applications

The novel TPAM hybrid membrane exhibited both lower vanadium permeability and higher proton conductivity than pristine SPEEK membrane.