2,203 research outputs found

    Ionic Conductive Membranes for Fuel Cells

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    This book, titled “Ionic Conductive Membranes for Fuel Cells”, from the journal Membranes, discusses the state of the art and future developments in the field of polymer electrolyte membranes for fuel cells, an efficient and clean system for converting fuel into energy

    Synthesis, modification of mesoporous carbons and their application in polymer electrolyte membrane fuel cells

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    Mesoporous carbon materials of carbon xerogel (CX) and silica-templated carbon (MC) were synthesized and explored as catalyst supports alternative to the most-commonly-used carbon black (CB) support, for polymer-electrolyte-membrane fuel cell (PEMFC) application. Pt catalyst was loaded on these carbons and electrodes were fabricated from them. These Pt-loaded carbon supports were characterized with XRD, TEM, ex-situ and in-situ cyclic voltammetry, etc. The fabricated electrodes were evaluated in single-cell testing in comparison with commercial CB-supported Pt catalyst fabricated electrodes. The experimental results showed that CX-supported Pt catalyst had close or better performance than that of CB-supported Pt, possibly due to CX\u27s 3-D porous structure, but MC had inferior performance to that of CB. MC\u27s high specific surface area, large pore size, high pore volume structure advantages did not transfer to a higher cell performance as expected. The reasons for MC support\u27s poor performance were discussed. Monofunctional fluorosulfonimide electrolyte (-C6H4SO2N(H)SO2CF3) was electrochemically grafted via its parent diazonium zwitterion onto planar glassy carbon electrode and the properties of the grafted layer on the electrode were investigated with electrochemical probes, XPS and chemical methods. The same monofunctional fluorosulfonimide electrolyte was also chemically grafted onto mesoporous CX and CB supports, a polymer electrolyte of sulfonated poly(arylene ether sulfone) was grafted onto CB support via the step-growth polymerization method. These monofunctional or polymeric electrolyte grafted mesoporous carbons were applied in PEMFC electrodes in the hope to increase three-phase zone and stability of the electrodes via covalently bonding of electrolyte onto electrodes. Single-cell testing results of MEAs made from these Pt-loaded, the sulfonimide-grafted CX or the polysulfone-electrolyte-grafted CB supports showed unexpectedly lower performance than that of un-graft commercial Pt-loaded CB support. The reasons for the poor performance were explored. In addition, sulfonimide polymers prepared by blending two different equivalent weight (EW) plain sulfonimide polymers or crosslinking a low EW polymer were evaluated as membrane materials for PEMFCs in comparison with Nafion membranes. The results showed even blending the same sulfonimide polymer with different EWs might improve membrane performance, and cross-linking of low sulfonimide also improved the membrane. From current work, it is worth to mention, PEMFC is a complicated and delicate system, whose performance is a combination of many different, even conflicting parameters of the Pt catalyst, the catalyst support, the electrolyte in the electrode, the membrane, the gas diffusion layer, and others. For fair comparison of cell performance in PEMFCs, well-designed, well-controlled experiments and methods are needed

    Ionic Conductive Polymers for Electrochemical Devices

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    Increasing levels of pollution and climate change are pushing the scientific community towards more sustainable solutions for the conversion and storage of energy. This book is dedicated to ionic conductive polymers, fundamental components of devices such as fuel cells (FCs), redox flow batteries (RFBs), and electrolyzers that can help to significantly decrease the amount of greenhouse gases emission. The book focuses on commercial polymers such as Nafion, a benchmark for proton-conducting membranes, acid doped polybenzimidazole (PBI), or blended membranes containing hyperbranched poly(arylene ether sulfone (PAES)/Linear poly(phenylene oxide) (PPO) as anion exchange membranes (AEMs). Promising and low-cost sulfonated aromatic polymers (SAP), or solid polymer blend electrolytes (SPBEs) based on natural chitosan (CS) and methylcellulose (MC). This book is also reports some strategies to enhance mechanical stability, such as cross-linking (XL), or several techniques, including classical casting methods or electrospinning (ES). I am confident that this book will serve to further stimulate advances in this research area, in both the sectors of membranes and catalysts, the first is essential for the long-term functioning of the system, and the second for a drastic reduction in costs, especially in fuel cells

    Poly(2, 5-benzimidazole)-based polymer electrolyte membranes for high-temperature fuel cell applications

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    Polymer electrolyte membrane fuel cells (PEMFCs) are one of the most promising clean technologies under development. However, the main obstacles for commercialising PEMFCs are largely attributed to the technical limitations and cost of current PEM materials such as Nafion. Novel poly(2,5-benzimidazole) (ABPBI)/POSS based polymer composite electrolyte membranes with excellent mechanical and conductivity properties were developed in this project including (I) ABPBI, polybenzimidazole (PBI) and their copolymers were synthesised by solution polymerisation and their chemical structures were confirmed by FTIR and elemental analysis. ABPBI/ActaAmmonium POSS (ABPBI/AM) and ABPBI/TriSilanolPhenyl POSS (ABPBI/SO) composites were also synthesised in situ. High quality polymer and composite membranes were fabricated by a direct cast method; and (II) The mechanical and thermal properties, microstructure and morphology, water and H3PO4 absorbility and proton conductivity of phosphoric acid doped and undoped ABPBI and ABPBI/POSS composite membranes were investigated. SEM/TEM micrographs showed that a uniform dispersion of POSS nano particles in ABPBI polymer matrix was achieved. The best performances on both mechanical properties and proton conductivities were obtained from the ABPBI/AM composite membrane with 3 wt% of POSS (ABPBI/3AM). It was found that both the water and H3PO4 uptakes were increased significantly with the addition of POSS due to formation of hydrogen bonds between the POSS and H2O/H3PO4, which played a critical role in the improvement of the conductivity of the composite membranes at temperatures over 100oC. ABPBI/3AM membranes with H3PO4 uptake above 117% showed best proton conductivities at both hydrous and anhydrous conditions from room temperature to 160oC, which is comparable with the conductivity of commercial Nafion 117 at 20oC in water-saturated condition, indicating that these composite membranes could be excellent candidates as a polymer electrolyte membrane for high temperature applications. A new mechanism for illustrating the improved proton conductivity of composite membranes was also developed

    Electrospun polymer nanofibers: the booming cutting edge technology

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    Electrospinning has been recognized as a simple and efficient technique for the fabrication of ultrathin fibers from a variety of materials including polymers, composite and ceramics. Significant progress has been made throughout the past years in electrospinning and the resulting fibrous structures have been exploited in a wide range of potential applications. This article reviews the state-of-art of electrospinning to prepare fibrous electrode materials and polymer electrolytes based on electrospun membranes in the view of their physical and electrochemical properties for the application in lithium batteries. The review covers the electrospinning process, the governing parameters and their influence on fiber or membrane morphology. After a brief discussion of some potential applications associated with the remarkable features of electrospun membranes, we highlight the exploitation of this cutting edge technology in lithium batteries. Finally the article is concluded with some personal perspectives on the future directions in the fascinating field of energy storag

    Functional applications of electrospun nanofibers

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    With the rapid development of nanoscience and nanotechnology over the last two decades, great progress has been made not only in preparation and characterization of nanomaterials, but also in their functional applications. As an important one-dimensional nanomaterial, nanofibers have extremely high specific surface area because of their small diameters, and nanofiber membranes are highly porous with excellent pore interconnectivity. These unique characteristics plus the functionalities from the polymers themselves impart nanofibers with many desirable properties for advanced applications

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

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    [EN] 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 H-2/O-2 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 degrees 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 nano-composites. 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.This research is in the frame of Support Programme for Research and Development of the Polytechnic University of Valencia, and the Ministry of Science and for funding provided through the projects: ENE2015-69203-R. OSF thanks to CONACYT-Mexico for supporting this research with the grant 475920.Martínez-Casillas, D.; Solorza, O.; Mollá Romano, S.; Montero Reguera, ÁE.; Garcia Bernabe, A.; Compañ Moreno, V. (2019). Polymer-modified sulfonated PEEK ionomer membranes and the use of Ru3Pd6Pt as cathode catalyst for H2/O2 fuel cells. International Journal of Hydrogen Energy. 44(1):295-303. https://doi.org/10.1016/j.ijhydene.2018.09.217S29530344
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