Search

Aqueous organic flow batteries have attracted dramatic attention for stationary energy storage due to their resource sustainability and low cost. However, the current reported systems can normally be operated stably under a nitrogen or argon atmosphere due to their poor stability. Herein a stable air-insensitive biphenol derivative cathode, 3,3′,5,5′-tetramethylaminemethylene-4,4′-biphenol (TABP), with high solubility (>1.5 mol L−1) and redox potential (0.91 V vs. SHE) is designed and synthesized by a scalable one-step method. Paring with silicotungstic acid (SWO), an SWO/TABP flow battery shows a stable performance of zero capacity decay over 900 cycles under the air atmosphere. Further, an SWO/TABP flow battery manifests a high rate performance with an energy efficiency of 85% at a current density of 60 mA cm−2 and a very high volumetric capacity of more than 47 Ah L−1. This work provides a new and practical option for next-generation practical large-scale energy storage.

Variations in glacier meltwater in the source regions of the Tibetan Plateau's (TP) largest lake (Selin Co) and China's longest river (Yangtze River) regulate the local and downstream water balance under the warming climate. However, the magnitude of their variations over the past four decades is still unknown. Here, we examine long-term changes in glacier mass balance over 1976–2017 using KH-9 and CoSSC-TanDEM-X data. We find that the mean rate of glacier mass loss (GML) has accelerated from −0.21 ± 0.11 m a–1over 1976–2000, to −0.28 ± 0.14 m a–1over 2000–11, and subsequently to −0.48 ± 0.10 m a–1over 2011–17. Changes in temperature and precipitation are the major causes of GML. Over 1976–2017, the contribution of decadal GML to Tuotuohe sub-basin runoff ranges from 4.3 to 8.0%, while its contribution to increased lake volume change in Selin Co and Chibzhang Co-Dorsoidong Co ranges from 3.5 to 16.3% and 19.2 to 21.4%, respectively. The GML of source regions made relatively small contributions to river runoff and lake supply, but plays a vital role when precipitation decreases. The quantitative evaluation of the water balance for the sources of great rivers and lakes over the TP is therefore important for water resource management and hydrological cycle studies.

The preparation of polyelectrolytes with excellent stability in high alkaline conditions still faces several challenges. In this study, we report a novel imidazolium-ionized monomer PhIM [PF₆], modified by the propylbenzene group on the position of N1/N3, which can be copolymerized with 1,1,1-trifluoroacetone under superacid-catalyzed conditions. The main-chain poly(arylene–imidazolium) polymers with a controllable degree of functionalization, high molecular weight, and good solubility are successfully prepared without further postfunctionalization. Two copolymers (block-like and random) can also be prepared by introducing biphenyl as a comonomer and adjusting the feed order. Due to their different microstructures, the two copolymers exhibit different ion conduction behaviors, water absorption capacities, and mechanical properties. The obtained polymer membranes exhibit high hydroxide conductivities and high chemical stability even after treatment in a 10 M NaOH solution at 80 °C. In summary, we highlight a simple, effective, and low-cost strategy to prepare highly alkaline stable poly(arylene–imidazolium) polymers.

The development of anhydrous high-temperature proton-exchange membranes (HT-PEMs) combining durable high proton conductivity and modest mechanical properties is a huge challenge to macromolecular design and engineering. HT-PEMs with microporous structures, constructed by the inefficient chain packing of contorted and rigid polymer backbones with imidazole, are reported for the first time. It is found that the widespread and interconnected microporosity of the polymers endows the HT-PEMs with an excellent phosphoric acid (PA) doping level (ADL) and a corresponding superhigh proton conductivity, as well as suitable mechanical properties and PA-retention ability. An outstanding proton conductivity of 330.3 mS cm−1 is obtained at 180 °C under an anhydrous atmosphere, which is superior to those of reported HT-PEMs with far higher ADLs (

A novel microporous anion exchange membrane containing a spirobiindane segment and cardo moiety is successfully synthesized through superacid-catalyzed Friedel–Crafts-type polymerization. The devel...

Polymers of intrinsic microporosity (PIMs) with superhigh permeability have been widely studied for higher selectivity in the various separation processes. However, the disorder and wide-distributi...

Using eddy-covariance turbulence measurements over a Tibetan glacier, we present a description of scalar turbulence characteristics in the stable boundary layer. Interesting behaviours are demonstrated in terms of temperature–humidity de-correlation and dissimilarity. That is, a lack of perfect correlation occurs between the two scalars (i.e., correlation coefficients

Sulfonated covalent organic nanosheets (SCONs) with a functional group (−SO3H) are effective at reducing ion channels length and facilitating proton diffusion, indicating the potential advantage of SCONs in application for proton exchange membranes (PEMs). In this study, Nafion-SCONs composite membranes were prepared by introducing SCONs into a Nafion membrane. The incorporation of SCONs not only improved proton conductivity, but also suppressed methanol permeability. This was due to the even distribution of ion channels, formed by strong electrostatic interaction between the well dispersed SCONs and Nafion polymer molecules. Notably, Nafion-SCONs-0.6 was the best choice of composite membranes. It exhibited enhanced performance, such as high conductivity and low methanol permeability. The direct methanol fuel cell (DMFC) with Nafion-SCONs-0.6 membrane also showed higher power density (118.2 mW cm−2), which was 44% higher than the cell comprised of Nafion membrane (81.9 mW cm−2) in 2 M methanol at 60 °C. These results enabled us to work on building composite membranes with enhanced properties, made from nanomaterials and polymer molecules.

The Tibetan Plateau and its surroundings contain the largest number of glaciers outside the polar regions. In the past 100 years, the glaciers on the Tibetan Plateau and its surrounding areas have been retreating slowly. Since the 1990s, however, the state of glaciers has undergone abnormal changes. Compared with the data derived from the First Chinese Glacier Inventory (CGI) (1960s−1980s), the glacier volume in China decreased by approximately 20% and the glacier area was reduced by approximately 17.7%, based on the data derived from the Second CGI. In particular, the glacier mass loss of the small glaciers was characterized by an area less than 1 km2 and was more intensive than that of lager glaciers. Abnormal changes in the glaciers on the Tibetan Plateau and the surrounding areas are mainly reflected by the spatial pattern. Through the systematic analysis of the data on glacier area, terminal position, and mass balance changes, it was found that the glacier changes in the region experienced obvious spatial heterogeneity from 1990 to 2010. The “Karakoram glacier anomaly” in the eastern Pamir, Karakoram, and western Kunlun regions has exhibited slight mass stability or even glacier advance. However, the glaciers on the southeastern Tibetan Plateau experienced the most intensive and accelerated shrinkage. On the evaluated timescale, the state of glaciers on the Tibetan Plateau and its surroundings has undergone abnormal changes regarding the loss rate of glacier volume. In the past 50 years, most of the glaciers have had a negative mass balance. Moreover, the mass loss process has intensified, especially since the 1990s. It is estimated that the loss rate of glacier volume from the Tibetan Plateau was as large as −15.6 ± 10.1 Gt/a between 2003 and 2009. In addition to the abnormal changes in spatial patterns and temporal changes, the glaciers exhibited an abnormal change within the glacial system. The most significant variability within the glacier system was the abnormal change in the structure of glacier ice. Another abnormal change within the glacier system was that the glaciers showed a sustained slowdown concomitant with ice thinning. Abnormal warming at high altitudes is an important driver of abnormal changes in glaciers on the Tibetan Plateau and its surroundings. Moreover, these contrasting glacier behaviors on the Tibetan Plateau and surroundings are related to atmospheric circulation processes, especially interactions between the westerlies and the Indian Summer Monsoon. In addition, changes in glaciers on the Tibetan Plateau and its surroundings are closely related to the enhancement of human activities. The South Asian region on the southern slope of the Himalayas acts as a main source of severe anthropogenic aerosol emissions, especially that of black carbon. The black carbon transported from South Asia to the glaciers reduces the glacier’s albedo and thus accelerates glacier melting. As global warming intensifies, the abnormal glacier status will likely lead to more hazards, such as ice collapse and glacial lake outburst floods. To reduce the potential glacial risks on the Tibetan Plateau and surroundings, it is necessary to further strengthen the abilities of glacier monitoring and disaster prevention.

Glacier surface ablation and associated energy characteristics are important to glacier survival, but little is known about these on glaciers in the West Kunlun Mountains (WKM), Tibetan Plateau, mainly due to their inaccessibility. Based on the glacio-meteorological conditions and mass balance observations on the Guliya ice cap (GIC) in the WKM during 2015/’16, a distributed energy and mass balance model was applied to study the spatiotemporal variations of energy and mass balance on the GIC, and the response of mass balance to climate change. Modeled results revealed that compared to the Chongce glacier in the WKM which was observed to undergo a positive mass balance in the 1980s, the GIC suffered a small mass loss with an annual value of −0.193 ± 0.042 m water equivalent, and the equilibrium-line altitude has risen by approximately 70 m to locate at 6000 ± 19 m. Besides, over the entire observation period, the incoming energy supplied by net shortwave radiation was almost balanced by the energy loss through net longwave radiation, and most energy available for surface ablation was consumed by latent heat flux through sublimation, which became a significant feature of the energy balance on the GIC. Sensitivity experiments by changing model input data with synthetic climate scenarios, which were sampled from meteorological measurements and accounted for coupled climate variable perturbations, revealed that the mass balance of the GIC was more sensitive to the changes in moisture-related variables than that in temperature, and positive mass balance would only be given from scenarios with significantly increased annual precipitation and decreased air temperature compared to those observed in 2015/’16.

The lotus leaf has the Janus wettability and outstanding floatability at multiphase interface. The ingenious design on lotus leaf surfaces enlightens us to fabricate the superhydrophobic/superhydrophilic binary cooperative membrane. Making use of the poor permeability of the candle soot, deposition of a layer of candle soot enables to form the Janus membrane with anisotropic wettability on different surfaces. After fixed by the hydrophobic polymer, the superhydrophobic/superhydrophilic binary cooperative membranes are prepared successfully on various membranes, such as filter paper, cotton fabric and copper mesh. The Janus membrane exhibits excellent interfacial floatability at the immiscible oil–water interface as a separator, thus affording high-performance immiscible oil/water separation without applied external pressure.

A novel liquid-based Janus porous membrane system was developed through the simple infusion of water and oil within different surfaces. This generates a stable liquid-infusion interface that repels immiscible organic solvents and water, and itself floats at the oil/water interface as a separator. The developed membrane successfully acts as a simple alternative for high-performance liquid separation.

Porous membranes, which consist of air-filled or liquid-filled pores, provide a gating strategy for tunable multiphase selectivity separation, and exhibit tremendous application potential in fields involving intelligent liquid management. Herein, we report the fabrication of a novel asymmetric wettability Janus porous membrane (JPM) based on bio-inspired models that integrate the air-gate floating mechanism and adhesive proteins secreted by mussels to attach to material-independent surfaces. The JPM fabricated through this novel and straightforward methodology has distinct hydrophobic-hydrophilic properties and interfacial compatibility. These features were engineered for F-oil (lubricant oil, Dupont Krytox 105) infused F-free JPM membrane filtration. The hydrophilic layer infused with high-surface-energy water acts as a perfect barrier (liquid gating) preventing invasion of the low-surface-energy F-oil which was infused in the hydrophobic surface, protecting the F-oil in the JPM. This is the first report regarding F-oil infused membrane filtration using the F-free-membrane, which can overcome the limitations of F-substrates for F-oil infused filtration.

It is well recognized by the scientific community that the fog can be deposited and transported on asymmetric surfaces, thus numerous efforts have been made to create such surfaces. However, it is still challenging to design a surface capable of fast deposition and rapid transportation simultaneously. Herein, inspired by the asymmetric structure of cactus spines and the cooperative hydrophilic/hydrophobic regions of desert beetles, a superhydrophilic-hydrophobic integrated conical stainless steel needle (SHCSN) is fabricated by a facile method. This integrated needle surface combines the merits of the fast deposition of fog on hydrophobic region and then rapid transportation on superhydrophilic surface. The droplet average transportation velocity on SHCSN is greater than other types of surfaces because of large Laplace pressure and self-driven phenomenon at its superhydrophilic-hydrophobic boundary. The best fog harvest efficiency was realized by optimizing the length of the hydrophobic region using theoretical modeling and experimental exploration, whereas the robust superhydrophilic needle surface induced the increase of collection time. This SHCSN was realized to be more efficient in fog collection than uniform superhydrophilic, uniform hydrophobic/superhydrophobic needle surfaces.

The Tibetan glaciers are greatly affected by the circulations of the westerlies and the Indian summer monsoon (ISM), but the mechanisms remain to be elucidated. In this project, we investigated the surface energy and mass balance of the Qiangtang No.1 Glacier in the inland Tibetan Plateau. Combining 4-year mass balance and meteorological records near the equilibrium line altitude with an energy-based mass balance model, we found that the meteorological conditions, which determined the glacier surface ablation and mass accumulation, are critically linked to changes in the intensity of the westerlies and the ISM. The 4-year mass balance comparisons demonstrated that the enhancement of the ISM in June and July, especially June, greatly increases the mass accumulation but inhibits the glacial ablation in the melt season, shifting the mass balance in a positive direction. Moreover, the occurrence of the westerlies enhancement interrupts the dominance of the ISM in the melt season. The intensified westerlies in the early melt season (June) could not only reduce the mass accumulation but also enhance the mass loss in the following months. In addition, the enhancement of the westerlies in the main melt season (July) could also greatly influence the local meteorological conditions, with lower temperatures and humidity but higher wind speeds. Such meteorological changes significantly reduce glacial ablation because more energy is consumed by sublimation and/or evaporation, rather than surface melting. These findings will enhance our understanding of the mechanisms underlying gl

Membrane fouling in membrane filtration technology is the major obstacle in maximizing its efficiency leading to short membrane lifetime and high operating cost. Here we reported that the use of oxidized nanocarbon black (ONC) in the preparation of composite ultrafiltration membrane, suppresses the fouling together with improved hydrophilicity and water permeate flux. Nanocarbon black (NC) was oxidized using ammonium persulfate, while morphology, nature and extent of oxidized groups were determined through scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS), fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) and ion exchange capacity (IEC) measurement. The dispersion of the ONC was stable in organic solvent (NMP) and in DI water even after 6 months. Oxidized nanocarbon black was incorporated in polysulfone matrix to prepare nanocomposite membranes (CNC) through phase inversion method. The influence of ONC on surface morphology, surface chemical composition, hydrophilicity, mechanical strength, surface negative charge, porosity, ultrafiltration and antifouling characteristics were evaluated. The results showed that inclusion of 1.0 wt% ONC enhance water permeate flux from 188.5 to 307 L m−2 h−1, protein rejection up to 97.6%, highest flux recovery ratio of 89.4% after three cycle permeation and lowest irreversible fouling of 10.5%. Considering relatively low cost, excellent antifouling properties and mechanical strength of CNC membranes, make it potential candidate as antifouling membrane for water purification.

Glacial lake outburst floods (GLOFs) have recently become one of the primary natural hazards in the Himalayas. There is therefore an urgent need to assess GLOF hazards in the region. Cirenmaco, a moraine-dammed lake located in the upstream portion of Zhangzangbo valley, Central Himalayas, has received public attention after its damaging 1981 outburst flood. Here, by combining remote sensing methods, bathymetric survey and 2D hydraulic modeling, we assessed the hazard posed by Cirenmaco in its current status. Inter-annual variation of Cirenmaco lake area indicates a rapid lake expansion from 0.10 ± 0.08 km2 in 1988 to 0.39 ± 0.04 km2 in 2013. Bathymetric survey shows the maximum water depth of the lake in 2012 was 115 ± 2 m and the lake volume was calculated to be 1.8 × 107 m3. Field geomorphic analysis shows that Cirenmaco glacial lake is prone to GLOFs as mass movements and ice and snow avalanches can impact the lake and the melting of the dead ice in the moraine can lower the dam level. HEC-RAS 2D model was then used to simulate moraine dam failure of the Cirenmaco and assess GLOF impacts downstream. Reconstruction of Cirenmaco 1981 GLOF shows that HEC-RAS can produce reasonable flood extent and water depth, thus demonstrate its ability to effectively model complex GLOFs. GLOF modeling results presented can be used as a basis for the implementation of disaster prevention and mitigation measures. As a case study, this work shows how we can integrate different methods to GLOF hazard assessment.

Four guanidinuium-functionalized model compounds containing different substituent groups were prepared, and the substituent effects on the overall alkaline stability of the guanidinium cations were investigated. Based on the good alkaline stability of the model compounds, novel guanidinium-based anion exchange membranes (AEMs), GPP-co-PAEK x, with controlled microblock structures were subsequently designed and synthesized in good yield via a three step reaction that included a fluorophenyl-amine reaction, methylation and nickel (0)-catalyzed coupling. Notably, the use of a hydrophilic, guanidinium cation-containing component as a raw material in the direct synthesis of AEMs via nickel(0)-catalyzed coupling avoided using hygroscopic Vilsmeier salts and is obviously different from the conventional method that involves bromomethylation or post-quaternization. The GPP-co-PAEK x membranes exhibited lower water uptake values (≤23.4% at 60 °C) and hydroxide conductivities comparable to those of others reported randomly functionalized guanidinium-based AEMs with similar ion exchange capacity (IEC) values. This finding indicates that the GPP-co-PAEK x membranes with controlled microblock structures possess well-developed hydrophilic/hydrophobic nanophase separation, which was confirmed by transmission electron microscopy (TEM). Moreover, long-term alkaline stability tests demonstrated that the alkaline stability of both the hydrophilic guanidiniums groups and the copolymer backbone contributed to the good alkaline stabilities of the GPP-co-PAEK x membranes.

Fundamental problems in thin film composite (TFC) reverse osmosis (RO) membranes in terms of the interfacial adhesion between the support and the active layer, the impact of support surface pore characteristics on the active layer formation process and the accordingly obtained active layer properties were investigated. Paper studies mainly includes following aspects: Five types of polysulfone (PSf) supports with varied surface pore characteristic properties were prepared and characterized; Thin film composite (TFC) polyamide (PA) reverse osmosis (RO) membranes were fabricated on these supports via in situ interfacial polymerization (IP) technology under identical IP protocols, and the performance and properties of the obtained TFC membranes were investigated systematically; Three types of these supports produced TFC membranes with both good salt rejection and high water flux. On the other hand, two types of them produced TFC membranes with inferior salt rejection attributed to the delaminated active layer from the support; The root cause for the delamination was explored and a speculated mechanism model for it and for the impact of support surface pore characteristic on the active layer formation was proposed. Furthermore, profilometer was used for the first time to measure the accurate thickness of individual active layer to overcome the shortcomings of the conventional electron microscope technologies. The basic understanding of the interplay between the support and the active layer provides important information for developing of thin film composite (TFC) membranes with improved performance.

To design and construct high ionic conductive anion exchange membranes (AEMs), tetra-pyrrolidinium-based block poly(arylene ether sulfone)s were synthesized. Pyrrolidinium groups were densely and controllably introduced into the polymer scaffold using a novel tetra-functionalized monomer, 4, 4′-oxybis (2,6-bis(pyrrolidinyl-1-methyl) phenol) (OBBPYP), which was synthesized via the Mannich reaction. To obtain chemically stable pyrrolidinium cations, the alkaline stabilities of pyrrolidinium-based cationic model compounds with various N-substituted alkyl chains (methyl, ethyl, butyl) were studied using 1H nuclear magnetic resonance (1H NMR) spectroscopy, in which methyl as the N-substituent group exhibited the highest alkaline stability. Based on the results above, a targeted, well-controlled, multiblock structure AEM (QQBPES-2.4OH) with densely concentrated pyrrolidinium cations was obtained via an iodomethane quaternization reaction. The densely concentrated ionic groups provide ionic nanochannels for hydroxide conduction, and the hydrophobic polymer backbone is responsible for the critical membrane mechanical support. As confirmed by transmission electron microscopy (TEM) and small angle X-ray scattering (SAXS), the QQBPES-2.4OH membrane exhibited a more obvious hydrophilic-hydrophobic microphase structure, compared to the random di-pyrrolidinium cation-based AEM (DQRPES-2.4OH) and tetra-pyrrolidinium cation-based AEM (QQRPES-2.4OH). Moreover, the QQBPES-2.4OH membrane exhibited considerably higher hydroxide conductivity, up to 68.0 mS cm−1 at 80 °C, better flexibility and lower water swelling. The results of this work suggest a novel and scalable approach to the functionalization of polymers for AEMs.

Ultrafiltration membranes with integrated antimicrobial and antifouling properties were fabricated using an engineering thermoplastic (carboxylated cardopoly(aryl ether ketone, PEK-COOH). Different molecular weights of PEO (Mw: 120, 350, 550) were grafted to the PEK-COOH membrane surface via EDC/NHS methodology. N-chloramine modified membranes then were prepared by simple exposure to dilute sodium hypochlorite solution. The surface grafting processes were all performed in water (i.e. without organic solvent). With this surface modification, the hydrophilicity of membranes improved significantly and the pure water flux increased compared to the unmodified PEK-COOH membrane. Furthermore, the PEO and N-chloramine modified membranes were resistant not only to both protein adsorption and bacterial adhesion, but also to microbial proliferation. The results of this work suggest that PEO and N-chloramine modified membranes are promising as fouling-resistant membranes.

Using cation compounds as raw materials, three quaternized microblock poly(p-phenylene-co-aryl ether ketone)s (s-, m-, and l-QPP-co-PAEK) were synthesized using a nickel (0)-catalyzed coupling reaction. Hydrophilic and hydrophobic moieties were affixed using cationic quaternary ammonium (QA) groups attached to poly(p-phenylene) by a three-carbon interstitial spacer and nonionic dichloride monomers of various lengths, respectively. The morphology, water uptake, swelling ratio, mechanical properties, thermal stability, hydroxide conductivity and alkaline stability of these new membranes were investigated. Experimental results indicated that the membrane with the longest hydrophobic microblock exhibited high hydroxide conductivity (37.6 mS cm−1 at 80 °C) resulting from the aggregation of ionic clusters observed using TEM. The copolymers with longer hydrophobic nonionic segments exhibited improved alkaline stability, suggesting that the hydrophobic chain shields the QA groups and that the polymer chains pack in a manner that restricts rotation. Controlling the distribution of QA groups in poly(p-phenylene) moieties and tuning the block length of nonionic segments are demonstrated to be effective methods for improving the hydroxide conductivity and alkaline stability of anion exchange membranes.

Functionalized polysulfone (PSf) membranes with combined antibacterial and antifouling properties were fabricated by incorporating a poly(ethyleneoxide)-grafted (PEO-grafted) amphiliic polymer. Both antifouling and antibacterial groups were easily introduced onto the membrane surfaces through non-solvent induced phase separon process and a simple chlorination process. It was observed that the functionalized membranes were effectivatie in resisting both protein absorption and bacterial adhesion. Furthermore, the functionalized membrane (M3-Cl) showed mostly suppressed irreversible flux decline and a 97% flux recovery ratio after simple washing during the separation process, indicating excellent antifouling properties. Meanwhile, the functionalized PSf membrane exhibited efficient biocidal activity against E. coli and S. aureus. These modified functionalized PSf membranes also displayed outstanding properties in inhibiting the formation of biofilm. Moreover, the antibacterial feature was renewable by a simple process.

Directional liquid transport driven by the interface or surface property of Janus porous membrane owes great significance to many applications such as separation technology, fog collection, and energy devices. The Janus porous membranes have successfully demonstrated an efficient oil self-transport in water and also enable directional water transport in air or oil-water interface. However, the directional water transport in oil environment is a challenge because of the relatively low surface tension of oil. In this work, a novel integrated Janus porous membrane is developed for the first time to construct self-propelled energy free directional water transport in oil system that successfully demonstrated to be a facile “water diode” for under-oil water one-way regulation. Additionally, this Janus porous membrane exhibits an interesting tunable fluid-gating behavior for either water or oil, using optimized conditions. The current findings may promote the innovation towards directional liquid transport science and will open up new avenues for diverse on-demand liquids manipulation scenarios such as water-in-heavy oil emulsion separation.

The development of polymer exchange membranes (PEMs) with high proton conductivity under high temperature and low relative humidity (RH) conditions is important to the improvement of the comprehensive performance of the fuel cell. In this paper, we present a novel approach for the design of semi-crystalline fluorinated PEMs (FSPP-1) via Ni(0)-catalyzed coupling polymerization. The structural characteristics of FSPP-1 are composed of retaining a portion of the fluorinated matrix (coil units) and introducing aromatic π-π interactions in the hydrophilic block (rod units), as well as precisely controlling the same block length along the main chain axis, which is a similar, molecular-level approach as the prototypical Nafion™ 117. The morphology, water state, and proton conductivity of FSPP-1 were investigated in detail, and the results show higher proton conductivity at 40% RH at 80 °C. The study also revealed that a dense, narrow distribution of hydrophilic nanochannels were formed with good connectivity of the hydrophilic nanochannels in FSPP-1. More importantly, π-π interactions in the hydrophilic block and helical perfluoroalkyl chains in the hydrophobic block coexisted in FSPP-1 ionomers, forming more small and dense crystallite domains, which was found to be beneficial to improving the stability of the nanochannels at elevated temperature and low RH. This strategy to simultaneously increase the density of ion transport channels and high temperature stability provides a baseline for the molecular-level design of high temperature PEMs.

The poly(aryl ether ketone) with spatial cardo structure is prepared from 4,4′-bis(phenoxy)benzophenone and 1-(4-bromobutyl)indoline-2,3-dione through a facile polyhydroxyalkylation reaction catalyzed by superacid. The number average molecular weight of the resultant polymer is achieved as high as 105.6 kg mmol−1. Three anion exchange membranes were prepared by reacting the polymer with trimethylamine, N-methyl-piperidine, and N,N,N′,N′,N″-pentaethylguanidine, respectively. Among the prepared membranes, N-methyl-piperidine based anion exchange membrane exhibited the highest OH− conductivity of 99.8 mS cm−1 at corresponding IEC of 1.54 meq g−1. In addition, the prepared membranes also exhibit excellent mechanical properties, in which the tensile strength and elongation at break can reach up to 50 MPa and 35%, respectively. Moreover, the anion exchange membranes exhibited good alkaline stability. When they were treated with 1 M KOH at 60 °C for 600 h, their conductivity decreased by less than 5%.

Developing of polymeric material with high stability is the key to the progress of organic solvent nanofiltration (OSN) membranes. As a semi-crystalline polymer with rigid aromatic backbone structure, poly(ether ether ketone) (PEEK) has good resistance to most of the organic solvents. However, the preparation of PEEK asymmetric membranes is hindered by its inherent insolubility in common solvents. In this work, a chemical-induced crystallization (CIC) strategy involving fabrication of asymmetric membranes from its precursor polymer-poly(ether ether ketimine) (PEEKI) and then converting to PEEK by acid treatment was proposed. The results indicated that the obtained membranes could be used stably in various organic solvents, and the optimal membrane exhibited a DMF permeance of 4.19 L m-2 h-1 bar-1 and a molecular weight cut-off of 350 g mol−1 in DMF, which was an order of magnitude higher than the PEEK OSN membranes prepared from the sulfonic acid solvents. Meanwhile, the developed PEEK membranes also possessed good pressure resistance for long-term nanofiltration. Our study has proven the feasibility of fabrication PEEK asymmetric membranes through the CIC strategy for OSN application.

A self-assembly strategy has been developed for the synthesis of anion-exchange membranes (AEMs) with high alkaline stability. Cardo poly(aryl ether sulfone ketone)s with pendent tertiary amine groups were grafted with alkyl siloxane to form a polymer with cation quaternary ammonium groups. This polymer produced a zwitterionic polymer via partially hydrolysis of the alkyl siloxane in weak basic medium. The flexible and transparent zwitterionic polymer membranes possessing a Si-O-Si cross-linked network were prepared via the sol-gel polycondensation reaction and a self-assembly process. The homogeneous and continuous Si-O-Si cross-linked network inhibited membrane swelling and improved the mechanical properties and thermochemical stability. The membrane showed alkaline stability in 1 M NaOH aqueous solution at 60 °C for 600 h and solvent resistance in polar aprotic solvents (DMAc, NMP, and DMSO) at 60 °C for 30 days.

A series of tetra-sulfonated poly(p-phenylene-co-aryl ether ketone) membranes (l-tSPP-co-PAEK x) with microblock moieties have been synthesized by nickel (0) catalytic coupling copolymerization and show good dimensional stability. Compared with the mono-sulfonated poly(p-phenylene-co-aryl ether ketone) membranes (SPP-co-PAEKs), the relationships between water content, the state of water molecules, proton conductivity, methanol permeability, and morphology for the membranes are detailedly investigated. Analyses by small-angle X-ray scattering (SAXS) and transmission electron microscopy (TEM) show that the l-tSPP-co-PAEK x greatly facilitated the connected proton transport channel. The proton conductivity of l-tSPP-co-PAEK x membrane is up to 60.0 mS cm−1 at room temperature, which is 32% higher than that of the proton conduction in SPP-co-PAEKs, despite the IEC values are lower than that of the latter. The membranes exhibit high power densities in the range of 27.5–31.9 mW cm−2 for passive direct methanol fuel cells (DMFCs) at room temperature. The power density of l-SPP-co-PAEKs 1.20 is higher than that of commercial Nafion 115 (29.3 mW cm−2) and Nafion 117 (24.3 mW cm−2) under same test conditions. The desirable properties of l-tSPP-co-PAEK x membranes can be attributed to the synchronous introduction of locally and densely sulfonated hydrophilic units and hydrophobic microblock moieties in the membrane structure, resulting in the formation of the connected proton transport channel.

The bacteria-repellent and bactericidal functionalities in a single system are generally need to be carefully optimized in order to obtain the highest antibacterial performance. In this study, the controlled SI-PIMP strategy was developed for creating hierarchical polymer brushes possessing the bacteria-repellent and bactericidal functionalities. To obtain a bactericidal surface with minimal interference to its nonfouling property, optimization studies were conducted by facilely tailoring the surface density of the quaternary ammonium compound moieties through control over the monomer concentration. An optimal hierarchical polymer coating showed potent protein and bacteria repellence as well as certain bactericidal property. The longlasting antibacterial performance was also achieved due to the good balance between the dual functionalities. The tenability of the hierarchical polymer coating is applicable to surface chemistries for biosensors, molecular imaging, and biomedical applications.

Thin film composite nanofiltration membranes were fabricated by coating a water-soluble disulfonated poly(arylene ether sulfone) which contained pendant amine groups (SPES-NH2) onto a polysulfone support in conjunction with covalent crosslinking. Two different crosslinkers, glutaric dialdehyde (GA) and poly(ethylene glycol) diglycidyl ether (PEGDGE), were utilized with various concentrations and curing temperatures to optimize the performance of the resulting membranes. Both GA and PEGDGE crosslinked membranes exhibited optimal performance with a 1 wt.% polymer concentration and 90 °C curing temperature. In particular, the optimized PEGDGE crosslinked membranes exhibited a higher permeation flux of 25.5 ± 3.0 L m−2 h− 1 while that of the GA crosslinked membranes was 8.9 ± 3.2 L m−2 h− 1; each membrane exhibited similar levels of Na2SO4 rejection at 96.1 ± 1.1% and 96.6 ± 2.1%, respectively, at 4 bars. The higher flux for the PEGDGE crosslinked membranes was attributed to higher hydrophilicity. Furthermore, the rejection of methyl orange and methyl violet was above 99.9% for both the GA and PEGDGE crosslinked membranes. A fouling study of the PEGDGE crosslinked membrane was carried out using humic acid as a model foulant, and the membranes exhibited excellent antifouling ability, attributed to their high hydrophilicities and strongly anionic characteristics.

Thin film composite nanofiltration membranes were fabricated through dip-coating and in situ cross-linking of quaternized poly(ether ether ketone) containing a certain amount of tertiary amine groups (QAPEEKs) on polyacrylonitrile (PAN) support. The effects of the variables in membrane formation such as the coating polymer concentration, the curing temperature, and the cross-linking agent types on resultant membrane were studied and the membrane properties such as the barrier layer chemical structure, the surface element composition and morphology were investigated. The obtained performance of uncross-linked and cross-linked QAPEEK-70 thin film composites in nanofiltration test was compared. The results indicated that the cross-linking improved the composite membranes' performance. For instance, the membrane cross-linked by bisphenol A diglycidyl ether (BPADGE) named M-C-BPADGE exhibited a MgCl2 rejection of 97.8%, a water flux of 11.8Lm(-2)h(-1), a MWCO of 800Da and corresponding pore size of 0.69nm, while for its uncross-linked membrane named M-U, a MgCl2 rejection of 91.2%, a water flux of 13.5Lm(-2)h(-1), a MWCO with 960Da and a pore size of 0.77nm were found. Furthermore, the M-C-BPADGE membrane exhibited selectivities of 16.0 for separation of mixed Mg(2+) and Na(+) cations, much larger than selectivity of 5.2 obtained for M-U, suggesting that the cross-linked membranes are promising in cation separation.

It has been reported that introducing graphene oxide (GO) or functionalized GO into proton exchange membranes (PEMs) can inhibit methanol diffusion by increasing the complexity of the methanol diffusion pathway in the hydrophilic region. In fact, methanol permeation also occurs in the hydrophobic area, which is very important, but rarely studied. In this study, we propose a facile and effective in-situ cross-linking method to prepare GO/sulfonated poly (p-phenylene-co-aryl ether ketone) crosslinked PEMs. By using the sulfonic acid group in parent polymer as a solid acid catalyst, the –COOH groups in GO undergo the Friedel-Craft acylation with the nucleophilic phenyl rings in the hydrophobic segments under vacuum heating, and the construction of covalent cross-linking network between GO and hydrophobic region is achieved successfully. The obtained crosslinked membranes show obviously reduced methanol crossover and greatly enhanced selectivity. The highest power density of the passive DMFC is obtained by using the 2 wt% GO crosslinked membrane and its value (28.1 mW cm-2) is higher than the original parent polymer (24.4 mW cm-2). These results demonstrate that the hydrophobic phase is closely relevant to the transport of methanol molecules in the membrane, which provides a new idea for the construction of methanol-blocking PEMs.

The anion conductive polymers based on the aryl ether-free polyaromatics (poly[(fluorene alkylene)-co-(biphenyl alkylene)] (PFBA), poly(fluorene alkylene) (PFA)) and aryl ether-containing polyaromatics (poly(2,6-dimethyl-1,4-phenylene oxide) (PPO)) having various cation groups (quaternary ammonium (QA) or bulky imidazolium (MIm or PIm)) were designed and prepared to investigate the effect of polymer backbones and cation functional groups on the properties of anion exchange membranes (AEMs) in fuel cells. The PFBA AEM having bulky imidazolium group showed good mechanical properties while the PPO AEM with the same cation break into the pieces. The alkalinity of the bulky imidazoliums have determined to be weaker than that of the typical quaternary ammonium by the simulation. Thus, the high hydroxide conductivities of the AEMs based on the quaternary ammonium group have been observed. Although the alkaline stability testing in 2 mol L−1 NaOH at 80 °C indicated the AEMs based on the PFBA backbone are much more alkaline stable than that of the AEMs from PPO backbone, the PFA-QA having typical quaternary ammonium showed significant degradation signals in 2 mol L−1 NaOD CD3OD/D2O solution at 80 °C for 15 days while PFA-MIm with bulky imidazolium groups showed no degradation signal at the same testing condition. The single H2/O2 fuel cell testing at 60 °C suggested the polymer backbone and cations displayed significant effect on the fuel cell performance. The highest peak power density of 610 mW cm−2 was achieved for PFBA-QA-0.4 which is approximate twice as high as that of the PPO-QA-0.4 (351 mW cm−2) and also the PFBA-MIm-0.4 having bulky imidazolium (32 mW cm−2). The device durability test indicates that the voltage of PFBA-QA-0.4 membrane could be maintained above 0.7 V at 200 mA cm−2 for 74 h. These results suggested that the aryl ether-free polymer backbone would be a good choice for the high performance AEM designation, and the AEMs having alkaline stable bulky imidazoliums needed to be further investigated in detail to achieve excellent fuel cell performance.

In the overall alkaline stability for guanidinium cations, the substituted mode has been proven to play a very important role. Free and bulky alkyl substituents such as ethyl groups in guanidinium cations can provide large steric hindrance to resist the OH− attack and achieve much higher stability than conventional methyl-substituted ones. To obtain high-dimensional and good alkaline stabilities of anion exchange membranes (AEMs), linking the stable guanidiniums through suitable crosslinked structures (with different spacer structures or lengths) is a feasible strategy. In this study, bi-guanidinium-based crosslinked AEMs were prepared by Menshutkin reactions using brominated poly(2,6-dimethyl-phenylene oxide) and bi-guanidine crosslinkers followed by a complete quaternization of the remaining guanidine. The prepared membranes possess a low swelling ratio (

The porous 2D covalent organic nanosheets (CONs) membrane has become a new generation of membrane material due to its ultrahigh permeation flux. The main challenge in fabricating CONs membrane is how to exfoliate covalent organic frameworks (COFs) into large-scale, few-layer nanosheets. Herein, we presented a simple and economical azobenzene template approach for exfoliating 2D COFs into large nanosheets and achieved fabrication of ultrathin CONs membrane successfully. Three COFs with different skeleton structures were chosen to explore the influencing factors for effective exfoliating. We found that the compatibility between azobenzene molecules and COFs skeleton structure was the key point for exfoliation. When the COF skeleton matching with the azobenzene molecular structure, COFs can be easily exfoliated into larger-scale CONs than nanosheets prepared by conventional exfoliation methods. The as-exfoliated nanosheets membrane showed a higher water flux (596 L m2 h-1 bar-1) than a graphene oxide (GO) membrane (4.3 L m2 h-1 bar-1) and high rejection of dye molecules, due to the nano-channels perpendicular to the surface of the membrane.

A facile and tunable strategy is proposed to fabricate the Janus porous membrane (JPM) comprising hydrophobic and controlled-hydrophilic wetting surfaces. The control over the wettability of hydrophilic surface is well achieved by tuning the temperature, reaction time, and surface modification. The JPM has directional cross-plane water transport ability, which is demonstrated in water harvest. The prepared JPM exhibits an interesting cross-plane unidirectional selectivity for oil transport at oil-water interface. The synergistic effect developed due to the directional oil transport and charge-screening, which offered an efficient separation of both the heavy oil and light oil from oil-in-water emulsions utilizing large pore size JPM. This easy-to-prepare and tunable strategy endows the JPM with many practical applications that is important for the evolution of JPM from a scientific concept to practical materials in real world.

To study the effect of cation groups on the alkaline stability and other properties of anion exchange membranes (AEMs), common quaternary ammonium (QA), N-alicyclic quaternary ammonium and imidazolium cations with bulky substituents were grafted onto an aryl ether-free polyaromatic backbone synthesized via acid-catalyzed polyhydroxyalkylation. The size of cation groups is calculated by Gaussian. The size of bulky imidazolium (MIm) is much larger than QA and N-alicyclic quaternary ammonium (Py and Pi). Because of the large size of the cation groups, the chain entanglement density of AEM with bulky imidazolium (PFBA-MIm-0.4) is lower than other three membranes, resulting PFBA-MIm-0.4 displays the highest water uptake of 225.1% at 80 °C, whereas the IEC of PFBA-MIm-0.4 is the lowest (1.49 mmol g−1). Meanwhile, the toughness of the membranes decreases when the size of the cation group increases. AEM with common quaternary ammonium (PFBA-QA-0.4) exhibits the highest hydroxide conductivity of 142 mS cm−1 at 80 °C because it exhibits the highest ion exchange capacity (IEC). More interestingly, PFBA-QA-0.4 shows long term alkaline stability that is as good as that of the AEMs with alicyclic quaternary ammonium or bulky imidazolium, even in 5 mol L−1 aqueous NaOH at 80 °C; however, the small size of the substituents of common quaternary ammonium does not have steric hindrance that is as large as that of the substituents of alicyclic quaternary ammonium and bulky imidazolium. Therefore, we selected PFBA-QA-0.4 to prepare a membrane electrode assembly for the further study of alkaline H2/O2 fuel cell performance. The single H2/O2 fuel cell exhibits a peak power density as high as 559 mW cm−2 at 80 °C under 100% RH with 0.1 MPa backpressure. These results of the comparison of AEMs with different size cation groups give some insights for future directions in the development of advanced AEMs.

With global warming, hazards relating to glacial melt, such as glacial lake outburst floods, are becoming progressively more serious. However, glacial melt processes and their hydrological consequences are very poorly understood. This study collected glacier discharge data from the terminus of the Parlung No. 4 Glacier throughout the melt season (May-October) during 2008, 2010, 2011 and 2012 to study its specific hydrological characteristics. Time series and multivariate regression analyses were employed to investigate the relationships between discharge and meteorological factors involved, as well as their correlation to discharge estimations. The 0- to 3-day time series analysis showed that discharge rates were highly autocorrelated and that discharge was significantly positively correlated to air temperature, vapour pressure and daily incoming shortwave radiation as well as weakly positively correlated to precipitation. A multiple-regression exponential model using the independent variables of the daily mean temperature and the vapour pressure exclusively was applied to simulate daily discharge in the basin with a high degree of accuracy. On average, July yielded the maximum monthly mean discharge, followed by August. Discharge in July and August accounted for 53% of the total discharge during the main melt season. The daily cycle of discharge changed as the melt season progressed, reflecting hydrological processes and characteristics of snow melt and glacier ice/snow melt, as well as their transitional periods. Subsequently, regular variations in the characteristics of the diurnal cycle of discharge, storage and delay were observed as the melt season progressed. In addition, the reasons behind the inter-annual variation in the characteristics of discharge and glacier discharge from the Tibetan Plateau and its surrounding areas are compared and discussed. Copyright (c) 2015 John Wiley & Sons, Ltd.

Tibetan glaciers experience spatially heterogeneous changes, which call for further investigation of the mechanisms responsible from an energy and mass perspective. In this study, 2 year parallel observations (August 2010–July 2012) at 5665 m a.s.l. on Zhadang glacier (a subcontinental glacier) and 5202 m a.s.l. on Parlung No. 4 glacier (a maritime glacier) were used to reveal the drivers of surface energy and mass balance at these sites. Glacio-meteorological data show that air temperature and specific humidity were 1.7°C and 0.5 g kg−1lower on Zhadang glacier than on Parlung No. 4 glacier. The mass accumulation occurred primarily before the Indian summer monsoon onset on Parlung No. 4 glacier and after its onset on Zhadang glacier. Point net mass loss was 2.5 times larger on Parlung No. 4 glacier than on Zhadang glacier, mainly due to the difference in melt energy. Overall, the physical mechanisms controlling the mass and energy difference can be attributed to both the feedback role of surface albedo through different snow accumulation characteristics and longwave radiation emission of the atmosphere due to different meteorological backgrounds. Finally, a review of the few studies dealing with energy balance on the Tibetan glaciers describes the possible spatial characteristics requiring further investigation in the future on larger spatial and temporal scales.

A novel bisphenol monomer bearing a cyclic tertiary amine was prepared in good yields by the acid-catalyzed reaction of N-methyl-4-piperidone and phenol. Tertiary amine poly(aryl ether sulfone) (TAPES) with high molecular weights of up to 95.3 kg mmol−1 and good thermal stability was synthesized by nucleophilic substitution of the bisphenol monomer with 4,4′-dichlorodiphenyl sulfone. The spatial separation between the cyclic tertiary amine groups and the hydroxyl ortho-position improves the stability of the intermediate and was the key to the polymerization. The anion exchange membranes (AEMs) QPES or DQPES are obtained by quaternization of TAPES with methyl iodide or (3-bromopropyl)trimethylammonium bromide, respectively. DQPES (ion exchange capacity = 3.12 mmol g−1) shows a higher ion conductivity of 59.8 mS cm−1 and reasonable dimensional stability in water at 80 °C. DQPES membrane revealed that the high conductivity might be due to its phase-separated structure in small-angle X-ray scattering test. The alkaline stability of QPES and the methoxy-capped QPES was compared, end-capping was found to improve the stability of piperidinium cations. This method offers a versatile platform for cost-effective synthesis of piperidinium-based AEMs with poly (aryl ether) backbones, and may provide a strategy to improve alkaline stability.

In this study, we sought a better understanding of how the hydrophilicity of a polymer affects the morphology and performance of membranes. Three types of polymer with different hydrophilicity solution systems were considered: poly(aryl ether ketone) bearing a hydroxyl group (PEK–OH-100) with N,N-dimethylformamide (DMF); poly(aryl ether ketone) bearing a 50% fraction hydroxyl group with DMF, and cardo poly(aryl ether ketone) with DMF. These systems were used to investigate the evolution of the morphology and variation in performance versus a change in the hydrophilicity of the polymer. In addition, the fundamental thermodynamic influence of the solution systems on the phase-inversion process was investigated by cloud-point measurement and Hansen solubility parameter theory to determine the role of polymer hydrophilicity on the stability of the polymer solution in humid surroundings. The performance of the membranes was tested via testing of the pure water flux, porosity, and rejection of bovine serum albumin (BSA) with respect to variations in the polymer hydrophilicity, evaporation time, relative humidity, and molecular weight of the polymer. The resulting optimal membrane exhibited a flux of 329.3 L m−2 h−1 and a 99.3% rejection of BSA at a relative humidity of 90% and an evaporation time of 3 s. The hydrophilic PEK–OH-100 membranes have promising applications in protein separation and the porous support of reverse-osmosis membranes and so on. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44701.

In this study, a cardo poly(aryl ether ketone) ultrafiltration membrane containing an N-chloramine functional group (PEK-N-Cl membrane) was easily obtained via exposure of a cardo poly(aryl ether ketone) ultrafiltration membrane (PEK-NH membrane) to dilute sodium hypochlorite solution. The chlorination process did not harm membrane performance. In addition, the PEK-N-Cl membrane was stable in both air and water. The PEK-N-Cl membrane exhibited excellent antimicrobial properties against both Gram-negative and Gram-positive bacteria (i.e. E. coli and Bacillus subtilis, respectively). The PEK-N-Cl membrane provided 94.2% and 100% reduction of E. coli and Bacillus subtilis, respectively, within 30 min of contact times. Moreover, nearly 100% of the E. coli was killed after 2 h during the filtration process for the PEK-N-Cl membrane. In addition, the water flux decreased by 42% for the PEK-N-Cl membrane compared to 77.6% for the PEK-NH membrane after filtration of the E. coli solution and incubation on LB nutrient agar plate, indicating that the PEK-N-Cl membrane enhibits antifouling. Furthermore, the PEK-N-Cl membrane is recyclable via subsequent exposure to a sodium hypochlorite solution.