Imperial College London

Dr Qilei Song

Faculty of EngineeringDepartment of Chemical Engineering

Reader in Chemical Engineering
 
 
 
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Contact

 

+44 (0)20 7594 5623q.song Website CV

 
 
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Location

 

ACEX 409AACE ExtensionSouth Kensington Campus

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Summary

 

Publications

Publication Type
Year
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82 results found

Cannon CG, Klusener PAA, Petit LF, Wong T, Wang A, Song Q, Brandon NP, Kucernak ARJet al., 2024, Methylene blue in a high-performance hydrogen-organic rechargeable fuel cell, ACS Applied Energy Materials, Vol: 7, Pages: 2080-2087, ISSN: 2574-0962

A hydrogen-organic hybrid flow battery (FB) has been developed using methylene blue (MB) in an aqueous acid electrolyte with a theoretical positive electrolyte energy storage capacity of 65.4 A h L–1. MB paired with the versatile H2/H+ redox couple at the negative electrode forms the H2–MB rechargeable fuel cell, with no loss in capacity (5 sig. figures) over 30 100% discharge cycles of galvanostatic cycling at 50 mA cm–2, which shows excellent stability. A peak power density of 238 mW cm–2 has also been demonstrated by utilizing 1.0 M MB electrolyte. This represents a type of scalable electrochemical energy storage system with favorable properties in terms of material cost, stability, crossover management, and energy and power density, overcoming many typical limitations of organic-based redox FBs.

Journal article

High M, Song Q, Campbell KLS, Fennell PSet al., 2023, Layered double hydroxide‐derived copper‐based oxygen carriers for chemical looping applications: oxygen release kinetics and impact of loading on long‐term performance, Greenhouse Gases: science and technology, Vol: 13, Pages: 505-545, ISSN: 2152-3878

Chemical looping with oxygen uncoupling, a variant of chemical looping combustion, requires chemically and physically stable oxygen carriers over long-term redox cycling. Copper-based oxygen carriers are characterised by high oxygen release rates but experience sintering at high temperatures. The use of layered double hydroxides (LDHs), prepared via co-precipitation, as oxygen carrier precursors has been shown to effectively limit deactivation of copper-based mixed metal oxides (MMOs) over extended redox cycling. The LDH-derived MMOs have highly dispersed metal oxide within a stable support; the high dispersion of metals is due to the LDH precursor structure. In this work, a fluidised bed reactor (FBR) was used to study the intrinsic kinetics of oxygen release from CuO/MgAl2O4 oxygen carriers synthesised via the LDH-MMO design strategy. The long-term performance of MMOs with higher loadings of CuO, calcined from LDHs with higher Cu contents, was also investigated using an FBR. The intrinsic kinetics were determined using a kinetic model incorporating an effectiveness factor. By minimising the effects of intra- and inter-particle mass transfer, the activation energy and the pre-exponential factor of the lower loading MMOs were determined to be 51 ± 3 kJ mol−1 and 0.0567 s−1, respectively. All MMOs showed excellent stability over 100 redox cycles in a thermogravimetric analyser. However, the pH during co-precipitation of the LDHs affected the stability of the MMOs in an FBR. The MMOs calcined from LDHs synthesised at pH 9.5 disintegrated during operation, whilst those produced from LDHs synthesised at pH 11 maintained high conversion and physical integrity over 100 redox cycles. © 2023 The Authors. Greenhouse Gases: Science and Technology published by Society of Chemical Industry and John Wiley & Sons Ltd.

Journal article

Tan R, Wang A, Ye C, Li J, Liu D, Darwich BP, Petit L, Fan Z, Wong T, Alvarez-Fernandez A, Furedi M, Guldin S, Breakwell CE, Klusener PAA, Kucernak AR, Jelfs KE, McKeown NB, Song Qet al., 2023, Thin film composite membranes with regulated crossover and water migration for long-life aqueous redox flow batteries., Advanced Science, Vol: 10, Pages: 1-11, ISSN: 2198-3844

Redox flow batteries (RFBs) are promising for large-scale long-duration energy storage owing to their inherent safety, decoupled power and energy, high efficiency, and longevity. Membranes constitute an important component that affects mass transport processes in RFBs, including ion transport, redox-species crossover, and the net volumetric transfer of supporting electrolytes. Hydrophilic microporous polymers, such as polymers of intrinsic microporosity (PIM), are demonstrated as next-generation ion-selective membranes in RFBs. However, the crossover of redox species and water migration through membranes are remaining challenges for battery longevity. Here, a facile strategy is reported for regulating mass transport and enhancing battery cycling stability by employing thin film composite (TFC) membranes prepared from a PIM polymer with optimized selective-layer thickness. Integration of these PIM-based TFC membranes with a variety of redox chemistries allows for the screening of suitable RFB systems that display high compatibility between membrane and redox couples, affording long-life operation with minimal capacity fade. Thickness optimization of TFC membranes further improves cycling performance and significantly restricts water transfer in selected RFB systems.

Journal article

Wang A, Tan R, Liu D, Lu J, Wei X, Alvarez-Fernandez A, Ye C, Breakwell C, Guldin S, Kucernak AR, Jelfs KE, Brandon NP, McKeown NB, Song Qet al., 2023, Ion-selective microporous polymer membranes with hydrogen-bond and salt-bridge networks for aqueous organic redox flow batteries, Advanced Materials, Vol: 35, Pages: 1-12, ISSN: 0935-9648

Redox flow batteries (RFBs) have great potential for long-duration grid-scale energy storage. Ion conducting membranes are a crucial component in RFBs, allowing charge-carrying ions to transport while preventing the cross-mixing of redox couples. Commercial Nafion membranes are widely used in RFBs, but their unsatisfactory ionic and molecular selectivity as well as high costs limit the performance and the widespread deployment of this technology. To extend the longevity and reduce the cost of RFB systems, inexpensive ion-selective membranes are highly desired that concurrently deliver low ionic resistance and high selectivity towards redox-active species. In this work, high-performance RFB membranes are fabricated from blends of carboxylate- and amidoxime-functionalized polymers of intrinsic microporosity (PIMs) that exploit the beneficial properties of both polymers. The enthalpy-driven formation of cohesive interchain interactions, including hydrogen bonds and salt bridges, facilitates the microscopic miscibility of the blends, while ionizable functional groups within the sub-nanometer pores allow optimization of membrane ion transport functions. The resulting microporous membranes demonstrate fast cation conduction with low crossover of redox-active molecular species, enabling improved power ratings and reduced capacity fade in aqueous RFBs using anthraquinone and ferrocyanide as redox couples. This article is protected by copyright. All rights reserved.

Journal article

Mizrahi Rodriguez K, Wu W-N, Alebrahim T, Cao Y, Freeman BD, Harrigan D, Jhalaria M, Kratochvil A, Kumar S, Lee WH, Lee YM, Lin H, Richardson JM, Song Q, Sundell B, Thür R, Vankelecom I, Wang A, Wang L, Wiscount C, Smith ZPet al., 2022, Multi-lab study on the pure-gas permeation of commercial polysulfone (PSf) membranes: Measurement standards and best practices, Journal of Membrane Science, Vol: 659, Pages: 1-13, ISSN: 0376-7388

Gas-separation membranes are a critical industrial component for a low-carbon and energy-efficient future. As a result, many researchers have been testing membrane materials over the past several decades. Unfortunately, almost all membrane-based testing systems are home-built, and there are no widely accepted material standards or testing protocols in the literature, making it challenging to accurately compare experimental results. In this multi-lab study, ten independent laboratories collected high-pressure pure-gas permeation data for H2, O2, CH4, and N2 in commercial polysulfone (PSf) films. Equipment information, testing procedures, and permeation data from all labs were collected to provide (1) accepted H2, O2, CH4, and N2 permeability values at 35 °C in PSf as a reference standard, (2) statistical analysis of lab-to-lab uncertainties in evaluating permeability, and (3) a list of best practices for sample preparation, equipment set-up, and permeation testing using constant-volume variable-pressure apparatuses. Results summarized in this work provide a reference standard and recommended testing protocols for pure-gas testing of membrane materials.

Journal article

Wang A, Tan R, Breakwell C, Wei X, Fan Z, Ye C, Malpass-Evans R, Liu T, Zwijnenburg M, Jelfs K, McKeown N, Chen J, Song Qet al., 2022, Solution-processable redox-active polymers of intrinsic microporosity for electrochemical energy storage, Journal of the American Chemical Society, Vol: 144, Pages: 17198-17208, ISSN: 0002-7863

Redox-active organic materials have emerged as promising alternatives to conventional inorganicelectrode materials in electrochemical devices for energy storage. However, the deployment of redoxactive organic materials in practical lithium-ion battery devices is hindered by their undesired solubilityin electrolyte solvents, sluggish charge transfer and mass transport, as well as processing complexity.Here, we report a new molecular engineering approach to prepare redox-active polymers of intrinsicmicroporosity (PIMs) that possess an open network of sub-nanometer pores and abundant accessiblecarbonyl-based redox sites for fast lithium-ion transport and storage. Redox-active PIMs can be solutionprocessed into thin films and polymer-carbon composites with a homogeneously dispersedmicrostructure, while remaining insoluble in electrolyte solvents. Solution-processed redox-active PIMelectrodes demonstrate improved cycling performance in lithium-ion batteries with no apparent capacitydecay. Redox-active PIMs with combined properties of intrinsic microporosity, reversible redox activityand solution processability may have broad utility in a variety of electrochemical devices for energystorage, sensors and electronic applications.

Journal article

Ye C, Tan R, Wang A, Chen J, Comesaña Gándara B, Breakwell C, Alvarez-Fernandez A, Fan Z, Weng J, Bezzu CG, Guldin S, Brandon N, Kucernak A, Jelfs K, McKeown N, Song Qet al., 2022, Long-life aqueous organic redox flow batteries enabled by amidoxime-functionalized ion-selective polymer membranes, Angewandte Chemie International Edition, Vol: 61, ISSN: 1433-7851

Redox flow batteries (RFBs) based on aqueous organic electrolytes are a promising technology for safe and cost-effective large-scale electrical energy storage. Membrane separators are a key component in RFBs, allowing fast conduction of charge-carrier ions but minimizing the cross-over of redox-active species. Here, we report the molecular engineering of amidoxime-functionalized polymers of intrinsic microporosity (AO-PIMs) by tuning their polymer chain topology and pore architecture to optimize membrane ion transport selectivity. AO-PIM membranes are integrated with three emerging aqueous organic flow battery chemistries, and the synergetic integration of ion-selective membranes with molecular engineered organic molecules in neutral-pH electrolytes leads to significantly enhanced cycling stability.

Journal article

High M, Patzschke C, Zheng L, Zeng D, Xiao R, Fennell P, Song Qet al., 2022, Hydrotalcite-derived copper-based oxygen carrier materials for efficient chemical-looping combustion of solid fuels with CO2 capture, Energy and Fuels, Vol: 36, Pages: 11062-11076, ISSN: 0887-0624

Chemical-looping combustion (CLC) is a promising technology that utilizes metal oxides as oxygen carriers for the combustion of fossil fuels to CO2 and H2O, with CO2 readily sequestrated after the condensation of steam. Thermally stable and reactive metal oxides are desirable as oxygen carrier materials for the CLC processes. Here, we report the performance of Cu-based mixed oxides derived from hydrotalcite (also known as layered double hydroxides) precursors as oxygen carriers for the combustion of solid fuels. Two types of CLC processes were demonstrated, including chemical looping oxygen uncoupling (CLOU) and in situ gasification (iG-CLC) in the presence of steam. The Cu-based oxygen carriers showed high performance for the combustion of two solid fuels (a lignite and a bituminous coal), maintaining high thermal stability, fast reaction kinetics, and reversible oxygen release and storage over multiple redox cycles. Slight deactivation and sintering of the oxygen carrier occurred after redox cycles at an very high operation temperature of 985 °C. We expect that our material design strategy will inspire the development of better oxygen carrier materials for a variety of chemical looping processes for the clean conversion of fossil fuels with efficient CO2 capture.

Journal article

High M, Patzschke C, Zheng L, Zeng D, Gavalda Diaz O, Ding N, Chien KHH, Zhang Z, Wilson G, Berenov A, Skinner S, Campbell K, Xiao R, Fennell PAUL, Song Qet al., 2022, Precursor engineering of hydrotalcite-derived redox sorbents for reversible and stable thermochemical oxygen storage, Nature Communications, Vol: 13, ISSN: 2041-1723

Chemical looping processes based on multiple-step reduction and oxidation of metal oxideshold great promise for a variety of energy applications, such as CO2 capture and conversion, gasseparation, energy storage, and redox catalytic processes. Copper-based mixed oxides are one of themost promising candidate materials with a high oxygen storage capacity. However, the structuraldeterioration and sintering at high temperatures is one key scientific challenge. Herein, we report aprecursor engineering approach to prepare durable copper-based redox sorbents for use inthermochemical looping processes for combustion and gas purification. Calcination of the CuMgAlhydrotalcite precursors formed mixed metal oxides consisting of CuO nanoparticles dispersed in the MgAl oxide support which inhibits the formation of copper aluminates during redox cycling. The copperbased redox sorbents demonstrated enhanced reaction rates, stable O2 storage capacity over 500 redoxcycles at 900 °C, and efficient gas purification over a broad temperature range. We expect that ourmaterials design strategy has broad implications on synthesis and engineering of mixed metal oxides fora range of thermochemical processes and redox catalytic applications.

Journal article

Ye C, Wang A, Breakwell C, Tan R, Grazia Bezzu C, Hunter-Sellars E, Williams DR, Brandon NP, Klusener PAA, Kucernak AR, Jelfs KE, McKeown NB, Song Qet al., 2022, Development of efficient aqueous organic redox flow batteries using ion-sieving sulfonated polymer membranes., Nat Commun, Vol: 13

Redox flow batteries using aqueous organic-based electrolytes are promising candidates for developing cost-effective grid-scale energy storage devices. However, a significant drawback of these batteries is the cross-mixing of active species through the membrane, which causes battery performance degradation. To overcome this issue, here we report size-selective ion-exchange membranes prepared by sulfonation of a spirobifluorene-based microporous polymer and demonstrate their efficient ion sieving functions in flow batteries. The spirobifluorene unit allows control over the degree of sulfonation to optimize the transport of cations, whilst the microporous structure inhibits the crossover of organic molecules via molecular sieving. Furthermore, the enhanced membrane selectivity mitigates the crossover-induced capacity decay whilst maintaining good ionic conductivity for aqueous electrolyte solution at pH 9, where the redox-active organic molecules show long-term stability. We also prove the boosting effect of the membranes on the energy efficiency and peak power density of the aqueous redox flow battery, which shows stable operation for about 120 h (i.e., 2100 charge-discharge cycles at 100 mA cm-2) in a laboratory-scale cell.

Journal article

Xia Y, Ouyang M, Yufit V, Tan R, Regoutz A, Wang A, Mao W, Chakrabarti B, Kavei A, Song Q, Kucernak A, Brandon Net al., 2022, A cost-effective alkaline polysulfide-air redox flow battery enabled by a dual-membrane cell architecture, Nature Communications, Vol: 13, Pages: 1-13, ISSN: 2041-1723

With the rapid development of renewable energy harvesting technologies, there is a significant demand for long-duration energy storage technologies that can be deployed at grid scale. In this regard, polysulfide-air redox flow batteries demonstrated great potential. However, the crossover of polysulfide is one significant challenge. Here, we report a stable and cost-effective alkaline-based hybrid polysulfide-air redox flow battery where a dual-membrane-structured flow cell design mitigates the sulfur crossover issue. Moreover, combining manganese/carbon catalysed air electrodes with sulfidised Ni foam polysulfide electrodes, the redox flow battery achieves a maximum power density of 5.8 mW cm-2 at 50% state of charge and 55 °C. An average round-trip energy efficiency of 40% is also achieved over 80 cycles at 1 mA cm-2. Based on the performance reported, techno-economic analyses suggested that energy and power costs of about 2.5 US$/kWh and 1600 US$/kW, respectively, has be achieved for this type of alkaline polysulfide-air redox flow battery, with significant scope for further reduction.

Journal article

Yuan Z, Liang L, Dai Q, Li T, Song Q, Zhang H, Hou G, Li Xet al., 2022, Low-cost hydrocarbon membrane enables commercial-scale flow batteries for long-duration energy storage, Joule, Vol: 6, ISSN: 2542-4351

Flow batteries are promising for long-duration grid-scale energy storage. Future terawatt-scaledeployment of flow batteries will require substantial capital cost reduction, particularly low-costelectrolytes and hydrocarbon ion exchange membranes. However, integration of hydrocarbonmembranes with novel flow battery chemistries in commercial-scale stacks is yet to be demonstrated.Here we report the pilot scale synthesis and roll-to-roll manufacturing of sulfonated poly(ether etherketone) (SPEEK) membranes and demonstrate their high hydroxide conductivity and chemical stabilityin kW-scale alkaline-based flow batteries. After exposure to a 5 mol L-1 NaOH solution at 60 °C for 41 days,the SPEEK membrane still enabled a stable alkaline zinc-iron flow battery performance for more than 650cycles (more than 650 hours) at high current densities (80 to 160 mA cm-2). Furthermore, the membranewas integrated in flow battery stacks with power up to 4000 W, which demonstrated a high energyefficiency of 85.5% operated at 80 mA cm-2 and long term stable operation over 800 h as well assubstantial cost savings relative to Nafion membranes. This work illustrates a potential pathway formanufacturing and upscaling of next-generation cost-effective flow batteries based on low-costhydrocarbon membranes developed in past decades to translate to large scale applications for longduration energy storage.

Journal article

Patzschke CF, Boot-Handford ME, Song Q, Fennell PSet 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).

Journal article

Tuffnell JM, Morzy JK, Kelly ND, Tan R, Song Q, Ducati C, Bennett TD, Dutton SEet 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.

Journal article

Tuffnell J, Morzy JK, Tan R, Song Q, Ducati C, Bennett T, Dutton SEet al., 2020, Comparison of the Ionic Conductivity Properties of Microporous and Mesoporous MOFs Infiltrated with a Na-Ion Containing IL Mixture

<jats:p>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 8.4x10-6 and 1.6x10-5 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 detrimental effect of discontinuous and tortuous mesoporous pathways which show a limited contribution to the overall ionic conductivity. </jats:p><jats:p />

Journal article

Zuo P, Li Y, Wang A, Tan R, Liu Y, Liang X, Sheng F, Tang G, Ge L, Wu L, Song Q, McKeown NB, Yang Z, Xu Tet 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.

Journal article

Zhao EW, Liu T, Jónsson E, Lee J, Temprano I, Jethwa RB, Wang A, Smith H, Carretero-González J, Song Q, Grey CPet 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.

Journal article

Tan R, Wang A, Malpass-Evans R, Williams R, Zhao EW, Liu T, Ye C, Zhou X, Darwich BP, Fan Z, Turcani L, Jackson E, Chen L, Chong SY, Li T, Jelfs KE, Cooper AI, Brandon NP, Grey CP, McKeown NB, Song Qet 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.

Journal article

Tan R, Wang A, Malpass-Evans R, Williams R, Zhao EW, Liu T, Ye C, Zhou X, Darwich BP, Fan Z, Turcani L, Jackson E, Chen L, Chong SY, Li T, Jelfs KE, Cooper AI, Brandon NP, Grey CP, McKeown NB, Song Qet al., 2020, 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

Journal article

Jackson E, Miklitz M, Song Q, Tribello GA, Jelfs Ket 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.

Journal article

Madrid E, Lowe JP, Msayib KJ, McKeown NB, Song Q, Attard GA, Düren T, Marken Fet 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.

Journal article

Baaden M, Barboiu M, Borthakur MP, Chen C-L, Coalson R, Davis J, Freger V, Gong B, Helix-Nielsen C, Hickey R, Hinds B, Hirunpinyopas W, Horner A, Hou J-L, Hummer G, Iamprasertkun P, Kazushi K, Kumar M, Legrand Y-M, Lokesh M, Mi B, Mitra S, Murail S, Noy A, Nunes S, Pohl P, Song Q, Song W, Tornroth-Horsefield S, Vashisth Het al., 2018, Applications to water transport systems: general discussion, FARADAY DISCUSSIONS, Vol: 209, Pages: 389-414, ISSN: 1359-6640

Journal article

Baaden M, Barboiu M, Bill RM, Chen C-L, Davis J, Di Vincenzo M, Freger V, Fröba M, Gale PA, Gong B, Hélix-Nielsen C, Hickey R, Hinds B, Hou J-L, Hummer G, Kumar M, Legrand Y-M, Lokesh M, Mi B, Murail S, Pohl P, Sansom M, Song Q, Song W, Törnroth-Horsefield S, Vashisth H, Vögele Met al., 2018, Biomimetic water channels: general discussion., Faraday Discuss, Vol: 209, Pages: 205-229

Journal article

Baaden M, Borthakur MP, Casanova S, Coalson R, Freger V, Gonzalez M, Góra A, Hinds B, Hirunpinyopas W, Hummer G, Kumar M, Lynch C, Murail S, Noy A, Sansom M, Song Q, Vashisth H, Vögele Met al., 2018, The modelling and enhancement of water hydrodynamics: general discussion., Faraday Discuss, Vol: 209, Pages: 273-285

Journal article

Houghton A, Tan R, Wang A, Song Qet al., 2018, Metal-Organic Framework Composite Membranes for Energy Storage Applications, UK MOF Symposium

Conference paper

Wang A, Tan R, Malpass-Evans R, McKeown N, Song Qet al., 2018, Polymer Membranes of Intrinsic Microporosity for Molecular Separations and Energy Storage, UK MOF Symposium

Conference paper

Hodgson P, Sceats M, Majumder K, Hills T, Song Q, Fennel P, Gao R, Tan R, MacFarlane D, Forsyth M, Howlett Pet al., 2018, Nano-active electrode materials, Pages: 373-374

Conference paper

Jiang S, Song Q, Hasell T, Cooper Aet 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

Conference paper

Jiang S, Song Q, Massey A, Chong SY, Chen L, Sun S, Hasell T, Raval R, Sivaniah E, Cheetham AK, Cooper AIet al., 2017, Oriented Two‐Dimensional Porous Organic Cage Crystals, Angewandte Chemie, Vol: 129, Pages: 9519-9523, ISSN: 0044-8249

<jats:title>Abstract</jats:title><jats:p>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.</jats:p>

Journal article

Jiang S, Song Q, Massey A, Chong SY, Chen L, Sun S, Hasell T, Raval R, Sivaniah E, Cheetham AK, Cooper AIet al., 2017, Oriented 2D porous organic cage crystals, Angewandte Chemie - International Edition, Vol: 56, Pages: 9391-9395, ISSN: 1433-7851

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.

Journal article

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