A Review on Sulfonated Polymer Composite/Organic-Inorganic Hybrid Membranes to Address Methanol Barrier Issue for Methanol Fuel Cells

This paper focuses on a literature analysis and review of sulfonated polymer (s-Poly) composites, sulfonated organic, inorganic, and organic−inorganic hybrid membranes for polymer electrolyte membrane fuel cell (PEM) systems, particularly for methanol fuel cell applications. In this review, we focused mainly on the detailed analysis of the distinct segment of s-Poly composites/organic−inorganic hybrid membranes, the relationship between composite/organic− inorganic materials, structure, and performance. The ion exchange membrane, their size distribution and interfacial adhesion between the s-Poly composites, nanofillers, and functionalized nanofillers are also discussed. The paper emphasizes the enhancement of the s-Poly composites/organic−inorganic hybrid membrane properties such as low electronic conductivity, high proton conductivity, high mechanical properties, thermal stability, and water uptake are evaluated and compared with commercially available Nafion® membrane

Study on Thermal Decomposition Behaviors of Terpolymers of Carbon Dioxide, Propylene Oxide, and Cyclohexene Oxide

The terpolymerization of carbon dioxide (CO2), propylene oxide (PO), and cyclohexene oxide (CHO) were performed by both random polymerization and block polymerization to synthesize the random poly (propylene cyclohexene carbonate) (PPCHC), di-block polymers of poly (propylene carbonate⁻cyclohexyl carbonate) (PPC-PCHC), and tri-block polymers of poly (cyclohexyl carbonate⁻propylene carbonate⁻cyclohexyl carbonate) (PCHC-PPC-PCHC). The kinetics of the thermal degradation of the terpolymers was investigated by the multiple heating rate method (Kissinger-Akahira-Sunose (KAS) method), the single heating rate method (Coats-Redfern method), and the Isoconversional kinetic analysis method proposed by Vyazovkin with the data from thermogravimetric analysis under dynamic conditions. The values of ln k vs. T−1 for the thermal decomposition of four polymers demonstrate the thermal stability of PPC and PPC-PCHC are poorer than PPCHC and PCHC-PPC-PCHC. In addition, for PPCHC and PCHC-PPC-PCHC, there is an intersection between the two rate constant lines, which means that, for thermal stability of PPCHC, it is more stable than PCHC-PPC-PCHC at the temperature less than 309 °C and less stable when the decomposed temperature is more than 309 °C. Pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) and thermogravimetric analysis/infrared spectrometry (TG/FTIR) techniques were applied to investigate the thermal degradation behavior of the polymers. The results showed that unzipping was the main degradation mechanism of all polymers so the final pyrolysates were cyclic propylene carbonate and cyclic cyclohexene carbonate. For the block copolymers, the main chain scission reaction first occurs at PC-PC linkages initiating an unzipping reaction of PPC chain and then, at CHC⁻CHC linkages, initiating an unzipping reaction of the PCHC chain. That is why the T−5% of di-block and tri-block polymers were not much higher than that of PPC while two maximum decomposition temperatures were observed for both the block copolymer and the second one were much higher than that of PPC. For PPCHC, the random arranged bulky cyclohexane groups in the polymer chain can effectively suppress the backbiting process and retard the unzipping reaction. Thus, it exhibited much higher T−5% than that of PPC and block copolymers

Continuous Dimethyl Carbonate Synthesis from CO2 and Methanol Using Cu-Ni@VSiO as Catalyst Synthesized by a Novel Sulfuration Method

Conversion of carbon dioxide into useful chemicals is a valuable task. One way to perform it is to transform CO2 into dimethyl carbonate (DMC) by a reaction with methanol. Catalyst exerts significant impact on this process. During this work, Cu-Ni@VSiO bimetallic catalysts were successfully synthesized by traditional solution and novel sulfuration methods. The catalytic materials were characterized by several analytical techniques and were tested in a continuous fixed-bed reactor under different reaction conditions to promote DMC synthesis from CO2 and methanol in the absence of dehydrating agents. The effects of reaction temperature, pressure, space velocity, metal loading, and bulk density on the catalytic performance were investigated in detail. It was found that the activity of Cu-Ni@VSiO catalyst with the support obtained by the novel sulfuration method is about three times higher when compared to that of the catalyst with the support that is synthesized by the traditional solution method. This result may stem from the difference in microstructure of the studied catalytic materials

Non-Isothermal Crystallization Kinetics of Montmorillonite/Polyamide 610 Nanocomposites

Non-isothermal crystallization kinetics of montmorillonite (MMT)/polyamide 610 (PA610) composites were readily prepared by in situ melt polymerization followed by a full investigation in terms of their microstructure, performance, and crystallization kinetics. The kinetic models of Jeziorny, Ozawa, and Mo were used in turn to fit the experimental data, in all of which Mo’s analytical method was found to be the best model for the kinetic data. Differential scanning calorimetry (DSC) and transmission electron microscopy (TEM) studies were used to investigate the isothermal crystallization behavior and MMT dispersion levels in the MMT/PA610 composites. The experiment results revealed that low MMT content can promote the PA610 crystallization, whilst high MMT content result in MMT agglomeration, and reduce the PA610 crystallization rate

3D Network Structural Poly (Aryl Ether Ketone)-Polybenzimidazole Polymer for High-Temperature Proton Exchange Membrane Fuel Cells

Poor mechanical property is a critical problem for phosphoric acid-doped high-temperature proton exchange membranes (HT-PEMs). In order to address this concern, in this work, a 3D network structural poly (aryl ether ketone)-polybenzimidazole (PAEK-cr-PBI) polymer electrolyte membrane was successfully synthesized through crosslinking reaction between poly (aryl ether ketone) with the pendant carboxyl group (PAEK-COOH) and amino-terminated polybenzimidazole (PBI-4NH2). PAEK-COOH with a poly (aryl ether ketone) backbone endows superior thermal, mechanical, and chemical stability, while PBI-4NH2 serves as both a proton conductor and a crosslinker with basic imidazole groups to absorb phosphoric acid. Moreover, the composite membrane of PAEK-cr-PBI blended with linear PBI (PAEK-cr-PBI@PBI) was also prepared. Both membranes with a proper phosphoric acid (PA) uptake exhibit an excellent proton conductivity of around 50 mS cm-1 at 170°C, which is comparable to that of the well-documented PA-doped PBI membrane. Furthermore, the PA-doped PAEK-cr-PBI membrane shows superior mechanical properties of 17 MPa compared with common PA-doped PBI. Based upon these encouraging results, the as-synthesized PAEK-cr-PBI gives a highly practical promise for its application in high-temperature proton exchange membrane fuel cells (HT-PEMFCs)

Effect of In-Situ Dehydration on Activity and Stability of Cu–Ni–K2O/Diatomite as Catalyst for Direct Synthesis of Dimethyl Carbonate

An in-situ dehydrating system built in a continuous flow fixed-bed bubbling reactor for direct synthesis of dimethyl carbonate (DMC) was designed. 3A molecular sieve (MS) was selected as the ideal dehydrating agent and the water trapping efficiency was studied. The effect of dehydrating agent/catalyst ratio, the dehydrating temperature and pressure, as well as the space velocity on the direct DMC synthesis catalyzed by K2O-promoted Cu–Ni was further investigated. These results demonstrated that 3A MS could effectively dehydrate the reaction system at the optimal conditions of 120 °C and 1.0 MPa with gas space velocity (GHSV) of 600 h−1, thereby greatly shifting the reaction equilibrium toward high DMC yield. Higher DMC yield of 13% was achieved compared with undehydrated reaction. Moreover, the catalyst can be highly stabilized by 3A MS dehydration with stable performs over 22 h

Performance Enhanced SAPO-34 Catalyst for Methanol to Olefins: Template Synthesis Using a CO2-Based Polyurea

Introducing mesopores into the channels and cages of conventional micropores CHA (Chabazite) topological structure SAPO-34 molecular sieves can effectively improve mass transport, retard coke deposition rate and enhance the catalytic performance for methanol to olefins (MTO) reaction, especially lifetime and olefins selectivity. In order to overcome the intrinsic diffusion limitation, a novel CO2-based polyurea copolymer with affluent amine group, ether segment and carbonyl group has been firstly applied to the synthesis of SAPO-34 zeolite under hydrothermal conditions. The as-synthesized micro-mesoporosity SAPO-34 molecular sieve catalysts show heterogeneous size distribution mesopores and exhibit slightly decrease of BET surface area due to the formation of defects and voids. Meanwhile, the catalysts exhibit superior catalytic performance in the MTO reaction with more than twice prolonged catalytic lifespan and improvement of selectivity for light olefins compared with conventional microporous SAPO-34. The methodology provides a new way to synthesize and control the structure of SAPO-34 catalysts

Graphene-encapsulated sulfur (GES) composites with a core-shell structure as superior cathode materials for lithium-sulfur batteries

Relatively uniform sized graphene-encapsulated sulphur (GES) composites with a core (S)-shell (graphene) structure were synthesized in one pot based on a solution-chemical reaction-deposition method. These novel GES particles were characterized by XRD, Raman spectrometry, SEM, TGA, EDS and TEM. The electrochemical tests showed that the present GES composites exhibit high specific capacity, good discharge capacity retention and superior rate capability when they were employed as cathodes in rechargeable Li-S cells. A high sulphur content (83.3 wt%) was obtained in the GES composites. Stable discharge capacities of about 900, 650, 540 and 480 mA h g(-1) were achieved at 0.75, 2.0, 3.0 and 6.0 C, respectively. The good electrochemical performance is attributed to the high electrical conductivity of the graphene, the reasonable particle size of sulphur particles, and the core-shell structures that have synergistic effects on facilitating good transport of electrons from the poorly conducting sulphur, preserving fast transport of lithium ions to the encapsulated sulphur particles, and alleviating the polysulfide shuttle phenomenon. The present finding may provide a significant contribution to the enhancement of cathodes for the lithium-sulphur battery technology

Specially designed carbon black nanoparticle-sulfur composite cathode materials with a novel structure for lithium-sulfur battery application

Abstract Sulfur is a promising cathode material with a high theoretical capacity of 1672 mAh g-1, but the challenges of the low electrical conductivity of sulfur and the high solubility of polysulfide intermediates still hinder its practical application. In this work, we design and synthesize a special carbon black nanoparticle-sulfur composite cathode material (NCB-S@NCB) with a novel structure and a high sulfur content of 84 wt% for lithium-sulfur battery application. The NCB-S@NCB composite cathode delivers a high initial discharge capacity of 1258 mAh g-1 and still maintains a reversible capacity of 865 mAh g-1 after 100 cycles with a relatively constant Coulombic efficiency around 98.0%. © 2015 Elsevier B.V. All rights reserved