69 results found
Patzschke CF, Boot-Handford ME, Song Q, et al., 2021, Co-precipitated Cu-Mn mixed metal oxides as oxygen carriers for chemical looping processes, Chemical Engineering Journal, Vol: 407, Pages: 1-14, ISSN: 1385-8947
Chemical looping with oxygen uncoupling (CLOU) and chemical looping air separation (CLAS) are novel and potentially promising processes for the combustion of solid fuels (e.g. biomass) for power generation with inherent CO2 capture. Redox-experiments at 850–950 °C confirmed that copper manganese spinel oxides are promising oxygen carriers for these processes, as they combine a relatively high O2 release capacity and fast O2 release kinetics. Furthermore, this work presents a novel method to calculate the O2 partial pressure equilibrium and the heat of O2 release from observed rates of reaction. To demonstrate this method, oxygen carriers were prepared via mechanical mixing and co-precipitation with varying molar Cu:Mn ratios and synthesis conditions, thereby tuning material properties and the pore structure. The precursors and calcined materials were characterised, and the crystalline phases were determined using X-ray diffraction. The insights from the post cycling analysis of the oxygen carriers and the experimentally obtained O2 release capacities were combined to elucidate the redox-reactions relevant for the two processes. It was found that the presence of a higher partial pressure of O2 during the O2 release results in the formation of different (perovskite-like) phases than those occurring during the decomposition in an O2-free environment. The oxygen carriers demonstrated excellent stability at CLOU and CLAS process conditions during extended redox cycling (100 cycles in a thermo-gravimetric analyser and 50 cycles in a fluidised bed reactor), showing no significant loss of reactivity or O2 release capacity and a high resistance towards attrition and agglomeration. The degree of degradation after 100 cycles was in the order: temperature swing (CLAS) < O2 partial pressure swing (CLOU) < reduction with CH4 (chemical looping combustion).
Tuffnell JM, Morzy JK, Kelly ND, et al., 2020, Comparison of the ionic conductivity properties of microporous and mesoporous MOFs infiltrated with a Na-ion containing IL mixture, Dalton Transactions: an international journal of inorganic chemistry, Vol: 49, Pages: 15914-15924, ISSN: 1477-9226
IL@MOF (IL: ionic liquid; MOF: metal–organic framework) materials have been proposed as a candidate for solid-state electrolytes, combining the inherent non-flammability and high thermal and chemical stability of the ionic liquid with the host–guest interactions of the MOF. In this work, we compare the structure and ionic conductivity of a sodium ion containing IL@MOF composite formed from a microcrystalline powder of the zeolitic imidazolate framework (ZIF), ZIF-8 with a hierarchically porous sample of ZIF-8 containing both micro- and mesopores from a sol–gel synthesis. Although the crystallographic structures were shown to be the same by X-ray diffraction, significant differences in particle size, packing and morphology were identified by electron microscopy techniques which highlight the origins of the hierarchical porosity. After incorporation of Na0.1EMIM0.9TFSI (abbreviated to NaIL; EMIM = 1-ethyl-3-methylimidazolium; TFSI = bis(trifluoromethylsulfonyl)imide), the hierarchically porous composite exhibited a 40% greater filling capacity than the purely microporous sample which was confirmed by elemental analysis and digestive proton NMR. Finally, the ionic conductivity properties of the composite materials were probed by electrochemical impedance spectroscopy. The results showed that despite the 40% increased loading of NaIL in the NaIL@ZIF-8micro sample, the ionic conductivities at 25 °C were 8.4 × 10−6 and 1.6 × 10−5 S cm−1 for NaIL@ZIF-8meso and NaIL@ZIF-8micro respectively. These results exemplify the importance of the long range, continuous ion pathways contributed by the microcrystalline pores, as well as the limited contribution from the discontinuous mesopores to the overall ionic conductivity.
Zuo P, Li Y, Wang A, et al., 2020, Sulfonated microporous polymer membranes with fast and selective ion transport for electrochemical energy conversion and storage, Angewandte Chemie International Edition, Vol: 59, Pages: 9564-9573, ISSN: 1433-7851
Membranes with fast and selective transport of protons and cations are required for a wide range of electrochemical energy conversion and storage devices, such as proton-exchange membrane (PEM) fuel cells and redox flow batteries. Here we report a new approach to designing solution-processable ion-selective polymer membranes with both intrinsic microporosity and ion-conductive functionality. This was achieved by synthesizing polymers with rigid and contorted backbones, which incorporate hydrophobic fluorinated and hydrophilic sulfonic acid functional groups, to produce membranes with negatively-charged subnanometer-sized confined ionic channels. The facilitated transport of protons and cations through these membranes, as well as high selectivity towards nanometer-sized redox-active molecules, enable efficient and stable operation of an aqueous alkaline quinone redox flow battery and a hydrogen PEM fuel cell. This membrane design strategy paves the way for producing a new-generation of ion-exchange membranes for electrochemical energy conversion and storage applications.
Zhao EW, Liu T, Jónsson E, et al., 2020, In situ NMR metrology reveals reaction mechanisms in redox flow batteries., Nature, Vol: 579, Pages: 224-228, ISSN: 0028-0836
Large-scale energy storage is becoming increasingly critical to balancing renewable energy production and consumption1. Organic redox flow batteries, made from inexpensive and sustainable redox-active materials, are promising storage technologies that are cheaper and less environmentally hazardous than vanadium-based batteries, but they have shorter lifetimes and lower energy density2,3. Thus, fundamental insight at the molecular level is required to improve performance4,5. Here we report two in situ nuclear magnetic resonance (NMR) methods of studying redox flow batteries, which are applied to two redox-active electrolytes: 2,6-dihydroxyanthraquinone (DHAQ) and 4,4'-((9,10-anthraquinone-2,6-diyl)dioxy) dibutyrate (DBEAQ). In the first method, we monitor the changes in the 1H NMR shift of the liquid electrolyte as it flows out of the electrochemical cell. In the second method, we observe the changes that occur simultaneously in the positive and negative electrodes in the full electrochemical cell. Using the bulk magnetization changes (observed via the 1H NMR shift of the water resonance) and the line broadening of the 1H shifts of the quinone resonances as a function of the state of charge, we measure the potential differences of the two single-electron couples, identify and quantify the rate of electron transfer between the reduced and oxidized species, and determine the extent of electron delocalization of the unpaired spins over the radical anions. These NMR techniques enable electrolyte decomposition and battery self-discharge to be explored in real time, and show that DHAQ is decomposed electrochemically via a reaction that can be minimized by limiting the voltage used on charging. We foresee applications of these NMR methods in understanding a wide range of redox processes in flow and other electrochemical systems.
Tan R, Wang A, Malpass-Evans R, et al., 2020, Hydrophilic microporous membranes for selective ion separation and flow-battery energy storage, Nature Materials, Vol: 19, Pages: 195-202, ISSN: 1476-1122
Membranes with fast and selective ion transport are widely used for water purification and devices for energy conversion and storage including fuel cells, redox flow batteries and electrochemical reactors. However, it remains challenging to design cost-effective, easily processed ion-conductive membranes with well-defined pore architectures. Here, we report a new approach to designing membranes with narrow molecular-sized channels and hydrophilic functionality that enable fast transport of salt ions and high size-exclusion selectivity towards small organic molecules. These membranes, based on polymers of intrinsic microporosity containing Tröger’s base or amidoxime groups, demonstrate that exquisite control over subnanometre pore structure, the introduction of hydrophilic functional groups and thickness control all play important roles in achieving fast ion transport combined with high molecular selectivity. These membranes enable aqueous organic flow batteries with high energy efficiency and high capacity retention, suggesting their utility for a variety of energy-related devices and water purification processes.
Tan R, Wang A, Malpass-Evans R, et al., 2019, Hydrophilic microporous membranes for selective ion separation and flow-battery energy storage (December, 10.1038/S41563-019-0536-8, 2019), NATURE MATERIALS, Vol: 19, Pages: 251-251, ISSN: 1476-1122
Jackson E, Miklitz M, Song Q, et al., 2019, Computational evaluation of the diffusion mechanisms for C8 aromatics in porous organic cages, The Journal of Physical Chemistry C: Energy Conversion and Storage, Optical and Electronic Devices, Interfaces, Nanomaterials, and Hard Matter, Vol: 123, Pages: 21011-21021, ISSN: 1932-7447
The development of adsorption and membrane-based separation technologies toward more energy and cost-efficient processes is a significant engineering problem facing the world today. An example of a process in need of improvement is the separation of C8 aromatics to recover para-xylene, which is the precursor to the widely used monomer terephthalic acid. Molecular simulations were used to investigate whether the separation of C8 aromatics can be carried out by the porous organic cages CC3 and CC13, both of which have been previously used in the fabrication of amorphous thin-film membranes. Metadynamics simulations showed significant differences in the energetic barriers to the diffusion of different C8 aromatics through the porous cages, especially for CC3. These differences imply that meta-xylene and ortho-xylene will take significantly longer to enter or leave the cages. Therefore, it may be possible to use membranes composed of these materials to separate ortho- and meta-xylene from para-xylene by size exclusion. Differences in the C8 aromatics’ diffusion barriers were caused by their different diffusion mechanisms, while the lower selectivity of CC13 was largely down to its more significant pore breathing. These observations will aid the future design of adsorbents and membrane systems with improved separation performance.
Madrid E, Lowe JP, Msayib KJ, et al., 2019, Triphasic nature of polymers of intrinsic microporosity (PIM-1 and PIM-PY) induces storage and catalysis effects in hydrogen and oxygen reactivity at electrode surfaces, ChemElectroChem, Vol: 6, Pages: 252-259, ISSN: 2196-0216
Hydrogen oxidation and oxygen reduction are two crucial energy conversion reactions, which are shown to be both strongly affected by the presence of intrinsically microporous polymer coatings on electrodes. Polymers of intrinsic microporosity (PIMs) are known to possess extremely high internal surface area and ability to bind gases under dry conditions. It is shown here that both, hydrogen‐ and oxygen gas binding into PIMs, also occurs under wet or “triphasic” conditions in aqueous electrolyte environments (when immersed in 0.01 M phosphate buffer at pH 7). For two known PIM materials (PIM‐1 and PIM‐PY), nanoparticles are formed by an anti‐solvent precipitation protocol and then cast as a film onto platinum or glassy carbon electrodes. Voltammetry experiments reveal evidence for hydrogen and oxygen binding. Both, PIM‐1 and PIM‐PY, locally store hydrogen or oxygen gas at the electrode surface and thereby significantly affect electrocatalytic reactivity. The onset of oxygen reduction on glassy carbon is shifted by 0.15 V in the positive direction.
Baaden M, Barboiu M, Borthakur MP, et al., 2018, Applications to water transport systems: general discussion, FARADAY DISCUSSIONS, Vol: 209, Pages: 389-414, ISSN: 1359-6640
Baaden M, Borthakur MP, Casanova S, et al., 2018, The modelling and enhancement of water hydrodynamics: general discussion., Faraday Discuss, Vol: 209, Pages: 273-285
Houghton A, Tan R, Wang A, et al., 2018, Metal-Organic Framework Composite Membranes for Energy Storage Applications, UK MOF Symposium
Wang A, Tan R, Malpass-Evans R, et al., 2018, Polymer Membranes of Intrinsic Microporosity for Molecular Separations and Energy Storage, UK MOF Symposium
Hodgson P, Sceats M, Majumder K, et al., 2018, Nano-active electrode materials, Pages: 373-374
Jiang S, Song Q, Hasell T, et al., 2017, Self-assembly of oriented 2D porous organic cage crystals, 254th National Meeting and Exposition of the American-Chemical-Society (ACS) on Chemistry's Impact on the Global Economy, Publisher: AMER CHEMICAL SOC, ISSN: 0065-7727
Jiang S, Song Q, Massey A, et al., 2017, Oriented Two‐Dimensional Porous Organic Cage Crystals, Angewandte Chemie, Vol: 129, Pages: 9519-9523, ISSN: 0044-8249
The formation of two-dimensional (2D) oriented porous organic cage crystals (consisting of imine-based tetrahedral molecules) on various substrates (such as silicon wafers and glass) by solution-processing is reported. Insight into the crystallinity, preferred orientation, and cage crystal growth was obtained by experimental and computational techniques. For the first time, structural defects in porous molecular materials were observed directly and the defect concentration could be correlated with crystal growth rate. These oriented crystals suggest potential for future applications, such as solution-processable molecular crystalline 2D membranes for molecular separations.
Ghalei B, Sakurai K, Kinoshita Y, et al., 2017, Enhanced selectivity in mixed matrix membranes for CO2 capture through efficient dispersion of amine-functionalized MOF nanoparticles, Nature Energy, Vol: 2, Pages: 1-9, ISSN: 2058-7546
Mixed matrix membranes (MMMs) for gas separation applications have enhanced selectivity when compared with the pure polymer matrix, but are commonly reported with low intrinsic permeability, which has major cost implications for implementation of membrane technologies in large-scale carbon capture projects. High-permeability polymers rarely generate sufficient selectivity for energy-efficient CO2 capture. Here we report substantial selectivity enhancements within high-permeability polymers as a result of the efficient dispersion of amine-functionalized, nanosized metal–organic framework (MOF) additives. The enhancement effects under optimal mixing conditions occur with minimal loss in overall permeability. Nanosizing of the MOF enhances its dispersion within the polymer matrix to minimize non-selective microvoid formation around the particles. Amination of such MOFs increases their interaction with thepolymer matrix, resulting in a measured rigidification and enhanced selectivity of the overall composite. The optimal MOF MMM performance was verified in three different polymer systems, and also over pressure and temperature ranges suitable for carbon capture.
Song Q, Wang A, Zhang TH, et al., 2017, Polymer Membranes of Intrinsic Microporosity for Molecular Separations, 13th International Conference on Materials Chemistry (MC13)
Zeng D, Patzschke C, Fennell P, et al., 2017, Nanostructured Iron-based Mixed Metal Oxides for Efficient H2 Production via Thermochemical Water Splitting, 13th International Conference on Materials Chemistry (MC13)
Song Q, 2017, Multifunctional Porous Materials and Membranes for Energy and Sustainability, 13th International Conference on Materials Chemistry (MC13)
Song Q, Liu TY, Jelfs KE, et al., 2017, Advanced Microporous Membranes for Molecular Separations, British Zeolite Association 40th Annual Meeting
Song Q, 2017, Functional Microporous Membranes for Energy and Environmental Applications, ChemEngDay UK 2017
Rong Y, Song Q, Mathwig K, et al., 2016, pH-Induced Reversal of Ionic Diode Polarity in 300 nm Thin Membranes Based on a Polymer of Intrinsic Microporosity, Electrochemistry Communications, Vol: 69, Pages: 41-45, ISSN: 1873-1902
“Ionic diode” (or current rectification) effects are potentially important for a range of applications including water purification. In this preliminary report, we observe novel ionic diode behaviour of thin (300 nm) membranes based on a polymer of intrinsic microporosity (PIM-EA-TB) supported on a poly-ethylene-terephthalate (PET) film with a 20 μm diameter microhole, and immersed in aqueous electrolyte media. Current rectification effects are observed for half-cells with the same electrolyte solution on both sides of the membrane for cases where cation and anion mobility differ (HCl, other acids, NaOH, etc.) but not for cases where cation and anion mobility are more alike (LiCl, NaCl, KCl, etc.). A pH-dependent reversal of the ionic diode effect is observed and discussed in terms of tentatively assigned mechanisms based on both (i) ion mobility within the PIM-EA-TB nano-membrane and (ii) a possible “mechanical valve effect” linked to membrane potential and electrokinetic movement of the membrane as well as hydrostatic pressure effects.
Jimenez-Solomon M, Song Q, Jelfs K, et al., 2016, Polymer nanofilms with enhanced microporosity by interfacial polymerization, Nature Materials, Vol: 15, Pages: 760-767, ISSN: 1476-4660
Highly permeable and selective membranes are desirable for energy-efficient gas and liquid separations.Microporous organic polymers have attracted significant attention in this respect owing to their highporosity, permeability, and molecular selectivity. However, it remains challenging to fabricate selectivepolymer membranes with controlled microporosity which are stable in solvents. Here we report a newapproach to designing crosslinked, rigid polymer nanofilms with enhanced microporosity bymanipulating the molecular structure. Ultra-thin polyarylate nanofilms with thickness down to 20 nmwere formed in-situ by interfacial polymerisation. Enhanced microporosity and higher interconnectivityof intermolecular network voids, as rationalised by molecular simulations, are achieved by utilisingcontorted monomers for the interfacial polymerisation. Composite membranes comprising polyarylatenanofilms with enhanced microporosity fabricated in-situ on crosslinked polyimide ultrafiltrationmembranes show outstanding separation performance in organic solvents, with up to two orders ofmagnitude higher solvent permeance than membranes fabricated with nanofilms made from noncontortedplanar monomers.
Song Q, Jiang S, Hasell T, et al., 2016, Molecular Sieves: Porous Organic Cage Thin Films and Molecular-Sieving Membranes (Adv. Mater. 13/2016), Advanced Materials, Vol: 28, Pages: 2652-2652, ISSN: 0935-9648
Song Q, Jiang S, Hasell T, et al., 2016, Porous organic cage thin films and molecular-sieving membranes, Advanced Materials, Vol: 28, Pages: 2629-2637, ISSN: 1521-4095
Porous organic cage molecules are fabricated into thin films and molecular-sieving membranes. Cage molecules are solution cast on various substrates to form amorphous thin films, with the structures tuned by tailoring the cage chemistry and processing conditions. For the first time, uniform and pinhole-free microporous cage thin films are formed and demonstrated as molecular-sieving membranes for selective gas separation.
Song Q, Cao S, Pritchard RH, et al., 2016, Nanofiller-tuned microporous polymer molecular sieves for energy and environmental processes, Journal of Materials Chemistry A, Vol: 4, Pages: 270-279, ISSN: 2050-7496
Microporous polymers with molecular sieving properties are promising for a wide range of applications in gas storage, molecular separations, catalysis, and energy storage. In this study, we report highly permeable and selective molecular sieves fabricated from crosslinked polymers of intrinsic microporosity (PIMs) incorporated with highly dispersed nanoscale fillers, including nonporous inorganic nanoparticles and microporous metal-organic framework (MOF) nanocrystals. We demonstrate that the combination of covalent crosslinking of microporous polymers via controlled thermal oxidation and tunable incorporation of nanofillers results in high performance membranes with substantially enhanced permeability and molecular sieving selectivity, as demonstrated in separation of gas molecules, for example, air separation (O2/N2), CO2 separation from natural gas (CH4) or flue gas (CO2/N2), and H2 separation from N2 and CH4. After ageing over two years, these nanofiller-tuned molecular sieves became more selective and less permeable but maintained permeability levels that are still two orders of magnitude higher than conventional gas separation membranes.
Jimenez-Solomon MF, Song Q, Jelfs KE, et al., 2016, Polymer nanofilms with enhanced microporosity by interfacial polymerisation for molecular separations
Song Q, 2015, Crosslinked polymer, method for producing the same, molecular sieve composition and material separation membranes
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