Investigating the factors that influence resistance rise of PIM-1 membranes in nonaqueous electrolytes

As redox active macromolecules are introduced to the materials repertoire of redox flow batteries (RFBs), nanoporous membranes, such as polymers of intrinsic microporosity (PIMs), are emerging as a viable separation strategy. Although their selectivity has been demonstrated, PIM-based membranes suffer from time-dependent resistance rise in nonaqueous electrolytes. Here, we study this phenomenon as a function of membrane thickness, electrolyte flow rate, and solvent washing using a diagnostic flow cell configuration. We find that the rate and magnitude of resistance rise can be significantly reduced through the combination of low electrolyte flow rate and solvent prewash. Further, our results indicate that, since the increase is not associated with irreversible chemical and structural changes, the membrane performance can be recovered via ex-situ or in-situ solvent washes. Keywords: Energy storage, Redox flow battery, Polymer of intrinsic microporosity, Size-exclusion membranes, Performance recovery, Cell resistanc

Titania Nanosheets / (TNS) Sulfonated Poly Ether Ether Ketone (SPEEK) composite proton exchange membranes (PEMs)

Sulfonated polyetheretherketone (SPEEK)-based composite membranes containing various amounts of titania nanosheets (TNS) as inorganic Filler have been prepared and investigated for proton exchange membrane applications. The SPEEK degree of sulfonation was DS = 0.58 and the TNS content was in the range 0.95-10.00 wt.%. The two-dimensional titanium oxide sheets, have been prepared as stable colloidal suspensions produced by the action of a quaternary ammonium ion, such as tetrabutylammonium, TBA(+), SPEEK/TNS composites have been prepared by casting from DMA (dimethylacctamide). The samples have been characterized in terms of thermal stability (TG/DTA, DSC), proton exchange capacity (P.E.C., by titration), water uptake, proton conductivity (EIS), and structural (XRD) and microstructural (SEM) features. Acid treated composites, at the lowest inorganic additive contents, exhibited improved properties in terms of proton conductivity and water uptake with respect to pure SPEEK. The best performing nanocomposite was the membrane containing only 1.67 wt.% TNS showing conductivity value of 4.14 10(-2) Scm(-1) at 140 degrees C and at 100% of relative humidity (RH), whereas pure SPEEK membrane exhibited a value of 1.76 x 10(-2) Scm(-1) at the same temperature and RH conditions. The volume swelling (VS), measured at 90 degrees C for the composite membrane containing 1.67 wt.% TNS, was reduced by ca. 80% with respect to that of a reference SPEEK membrane. The improved electrochemical properties of TNS nanocomposites have been associated to the unique nature of the two-dimensional nano structured inorganic additive

Development of glucose oxidase-based bioanodes for enzyme fuel cell applications

We fabricated an enzyme fuel cell (EFC)\ud device based on glucose as fuel and glucose oxidase (GOx)\ud as biocatalyst. As a strategy to improve GOx stability,\ud preserving at the same time the enzyme catalytic activity,\ud we propose an immobilization procedure to entrap GOx in\ud a polymer matrix based on Nafion and multiwalled carbon\ud nanotubes. Circular dichroism (CD) spectra were recorded\ud to study changes in the 3D structure of GOx that might be\ud generated by the immobilization procedure. The comparison\ud between the CD features of GOx immobilized and free\ud in solution indicates that the shape of the spectra and\ud position of peaks do not significantly change. The bioelectrocatalytic\ud activity toward glucose oxidation of\ud immobilized GOx was studied by cyclic voltammetry and\ud chronoamperometry experiments. Such electrochemical\ud experiments allow monitoring the rate of GOx-catalyzed\ud glucose oxidation and extrapolating GOx kinetic parameters.\ud Results demonstrate that immobilized GOx has high\ud catalytic efficiency, due the maintaining of regular and\ud well-ordered structure of the immobilized enzyme, as\ud indicated by spectroscopic findings. Once investigated the\ud electrode structure–property relationship, an EFC device\ud was assembled using the GOx-based bioanode, and sulfonated\ud poly ether ether ketone as electrolyte membrane.\ud Polarization and power density curves of the complete EFC\ud device were acquired, demonstrating the suitability of the\ud immobilization strategy and materials to be used in EFCsThe financial support of the Italian Ministry for Environment (MATTM, Project MECH2), the Ager Consortium and Fapesp/CNPq (Brazilian Funding Agencies) is gratefully acknowledged

Fabrication of proton conducting solid oxide fuel cell by using electrophoretic deposition

Anode-supported proton conducting solid oxide fuel cells (SOFCs) were fabricated by using electrophoretic deposition (EPD) for the electrolyte film deposition. BaCe0.9Y0.1O3-δ (BCY10) thick films were deposited on NiO-BCY10 substrates. The influence of the EPD parameters on the microstructure and electrical properties of BCY10 thick films was investigated. The anode substrates and electrolyte deposits were co-sintered at 1550°C for 2 h to obtain a dense electrolyte thick film, while keeping a suitable porosity in the anode. Innovative composites with La 0.8Sr0.2 Co0.8Fe0.2O3 (LSCF)-BaCe0.9Yb0.1O3-δ (10YbBC) composition were used as cathode materials. Prototype SOFCs were prepared by depositing the composite cathode on the co-sintered half cells. Fuel cell tests and electrochemical impedance spectroscopy (EIS) measurements were performed in the 550-700°C temperature range. The maximum power density of 296 mW cm -2 was achieved at 700°C

Sulfated zirconia S-ZrO2 doped Nafion® membranes for fuel cell applications

In this study, sulfonated zirconia was synthesized and incorporated into Nafion to improve its proton conductivity and water retention. Two types of nanometric superacidic sulonfated zirconia (S-ZrO2) were prepared by Sol Gel techniques. One (SZrO2 110) shows a tetragonal phase, the other (SZrO2 700) presents tetragonal and monoclinic phases. To investigate the effect of the SZrO2, preliminary Fuel Cell tests (Fig.1) were carried out at T = 70°C at different relative humidity (RH) using either Nafion-117 or composite membranes. While both cells exhibit better performances at higher RH, the Nafion/SZrO delivers the highest current values. Remarkably great improvements are observed for the composite when the comparison tests are run at low RH=50% this outlining the beneficial role of the SZrO2 additive. Water mobility and obstruction effects in the membranes were investigated with a combination of NMR variable temperature and pressure relaxation and pulsed field gradient (PFG) diffusion measurements

Deposition and electrochemical characterization of Yttrium doped Barium cerate and zirconate heterostructures

Epitaxial heterostructures consisting of an yttrium doped barium cerate, BaCe0.8Y0.2O3,(BCY) layer sandwiched between two yttrium doped barium zirconate, BaZr0.8Y0.2O3,(BZY) thin layers have been deposited on insulating (001) MgO substrates by pulsed laser deposition. The first BZY layer was aimed at improving the lattice match with the MgO substrate, the second at protecting the BCY layer. Ionic conductivity has been studied in the 300 degrees C-600 degrees C temperature range as a function of the BCY thickness in dry air and wet 5% H-2 in Ar atmosphere. In both atmospheres, heterostructures showed a conductivity slightly larger than that of BCY pellets sintered under optimized conditions. Such a result has been attributed to the absence of blocking grain boundaries in the epitaxial heterostructures due to their good crystallographic quality. The BCY sandwich heterostructures showed an improved chemical stability relative to standard BCY pellets

High efficiency CH3NH3PbI((3-x))Cl-x, perovskite solar cells with poly(3-hexylthiophene) hole transport layer

We fabricate perovskite based solar cells using CH3NH3PbI3-xClx with different hole-transporting materials. The most used 2,2',7,7'-tetrakis-(N,N-di-p-methoxyphenylamine)9,9'-spirobifluorene (Spiro-OMeTAD) has been compared to the poly(3-hexylthiophene-2,5-diyl) (P3HT). By tuning the energy level of P3HT and optimizing the device's fabrication, we reached 9.3% of power conversion efficiency, which is the highest reported efficiency for a solar cell using P3HT. This result shows that P3HT can be a suitable low cost hole transport material for efficient perovskite based solar cells. (C) 2013 Elsevier B.V. All rights reserved