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Liu X.,Beijing University of Chemical Technology | Zhou A.,Beijing University of Chemical Technology | Pan T.,Beijing University of Chemical Technology | Dou Y.,Beijing Key Laboratory for Green Catalysis and Separation | And 3 more authors.
Journal of Materials Chemistry A | Year: 2016

A hierarchical CoAl-OH layered double hydroxide (H-OH-LDH) electrode was prepared via a continuous calcination-rehydration treatment of a plate-like CoAl-CO3 layered double hydroxide (P-CO3-LDH) array on a nickel foil substrate. The H-OH-LDH electrode shows a well-defined hierarchical structure with a greatly increased accessible interlaminar surface area, leading to improved electrochemical energy storage ability. Most significantly, the interlayer space of H-OH-LDH acts as an electrolyte micro-reservoir to store OH- ions, which dramatically decreases the diffusion resistance of OH- to the inner surface of LDH lamella, and consequently results in an ultrahigh-rate-capability (capacitance reservation of 66% when the current density increases from 1 to 100 A g-1). The remarkable rate capability is superior to that of ever-reported transition metal oxide/hydroxide-based electrodes. In addition, an all-solid-state hybrid capacitor device was fabricated based on this H-OH-LDH electrode, exhibiting outstanding energy and power output (35.5 W h kg-1 at 27.3 kW kg-1) as well as excellent cycling stability. Therefore, this work demonstrates a new approach for the design and fabrication of LDH-based materials with self-generated electrolyte reservoirs, which have promising potential application in energy storage/conversion systems. © The Royal Society of Chemistry 2016. Source


Guo H.,Beijing University of Technology | Guo H.,Beijing Key Laboratory for Green Catalysis and Separation | Chen M.,Beijing University of Technology | Liu Q.,Beijing University of Technology | And 3 more authors.
Desalination | Year: 2015

The use of new polymeric building block is one of the important routes to extend the layer-by-layer (LbL) assembly technique to fabricate novel nanofiltration (NF) membrane. In this work, the low cost sulfonated cyclohexanone-formaldehyde (SCF) condensation polymer is used as anionic building blocks to prepare a novel positively charged nanofiltration membrane by LbL self-assembly technique. The LbL assembly process was investigated by XRD, FTIR, SEM and AFM measurements. The separation performance of cationic ions and dyes was evaluated by pressure-driven nanofiltration tests. It is found that the multilayer surfaces exhibited periodic variations in positive charges. And the prepared membrane showed an effective rejection of both cationic ions and dyes. The multilayer membrane of 4.5 bilayers exhibited rejections of 92.8% and 90.6% to Ni2+ and Ca2+, along with flux of 40.8 and 44.9L/(m2·h·MPa) and pure water flux of 49.3L/(m2·h·MPa), respectively. Simultaneously, this membrane also showed rejection of 93.7% and 90.8% to RdB and EbT, along with flux of 24.3 and 20.5L/(m2·h·MPa), respectively. Moreover, the long-term performance stability of the membrane was improved through cross-linking the multilayer membrane. © 2015 Elsevier B.V. Source


Li Y.,Beijing University of Technology | Li Y.,Beijing Key Laboratory for Green Catalysis and Separation | Qin Z.,Beijing University of Technology | Guo H.,Beijing University of Technology | And 6 more authors.
PLoS ONE | Year: 2014

In this work, the positively or negatively charged anatase TiO2 nanoparticles were synthesized via a low temperature precipitation-peptization process (LTPPP) in the presence of poly(ethyleneimine) (PEI) and poly(sodium4- styrenesulfonate) (PSS). X-ray diffraction (XRD) pattern and high-resolution transmission electron microscope (HRTEM) confirmed the anatase crystalline phase. The charges of the prepared TiO2, PEI-TiO2 and PSS-TiO2 nanoparticles were investigated by zeta potentials. The results showed that the zeta potentials of PEI-TiO2 nanoparticles can be tuned from +39.47 mV to +95.46 mV, and that of PSS-TiO2 nanoparticles can be adjusted from -56.63 mV to -119.32 mV. In comparison with TiO2, PSS-TiO2 exhibited dramatic adsorption and degradation of dye molecules, while the PEI modified TiO2 nanoparticles showed lower photocatalytic activity. The photocatalytic performances of these charged nanoparticles were elucidated by the results of UV-vis diffuse reflectance spectra (DRS) and the photoluminescence (PL) spectra, which indicated that the PSS-TiO2 nanoparticles showed a lower recombination rate of electron-hole pairs than TiO2 and PEI-TiO2. © 2014, Public Library of Science. All rights reserved. Source


Liu L.,Beijing Key Laboratory for Green Catalysis and Separation | Veerappan V.,University of North Texas | Bian Y.,Beijing Key Laboratory for Green Catalysis and Separation | Guo G.,Beijing Key Laboratory for Green Catalysis and Separation | Wang X.,Beijing Key Laboratory for Green Catalysis and Separation
Science China Chemistry | Year: 2015

We have previously developed bare narrow-bore capillary chromatography. In this work, high-performance DNA separation was realized for a size range of 10–800 base pairs (bp) utilizing bare narrow-bore capillary chromatography with 750 nm-radius capillaries. Separation behavior of double-stranded DNA (dsDNA) fragments was investigated over a range of eluent concentrations and elution pressures. DNA molecules were hydrodynamically separated in a size-dependent manner in free solution without any sieving matrices, with the longer fragments being eluted out from the capillary earlier. It was found that the eluent concentration variously influenced the transport behavior for different-sized DNA fragments depending upon the configuration of DNA molecules and the association of counterions. Ionic strength of the solutions strongly impacted DNA persistence length. Enhanced elution pressure could shorten analysis time with a slight loss in resolution. Excellent efficiency of two million theoretical plates per meter was achieved, which indicates the enormous potential of bare narrow-bore capillary chromatography for the analysis of DNA fragments. These findings would be useful in understanding the transport behavior of DNA fragments in confined dimensions for chromatography in free solution. © 2015 Science China Press and Springer-Verlag Berlin Heidelberg Source


Liu W.,Beijing University of Technology | Guo H.X.,Beijing University of Technology | Guo H.X.,Beijing Key Laboratory for Green Catalysis and Separation | Ji S.L.,Beijing University of Technology | And 4 more authors.
Express Polymer Letters | Year: 2015

The effective permselective pervaporation of alcohol is one of key technology for bio-alcohol industrial production. In this work, a new polydimethylsiloxane-block-polyphenylene oxide (PDMS-b-PPO) copolymer was first synthesized by a bridge reagent technique. Based on the copolymer structure confirmation, the asymmetric PDMS-b-PPO membrane was subsequently prepared by phase-inversion method in order to improve the anti-swelling capacity of PDMS. SEM observation indicated that the morphology of as-prepared membrane exhibited a ‘non-perforated’ structure, resulting from the phase-inversion and micro-phase separation of the PDMS-b-PPO copolymer in the membrane forming process. Furthermore, the structure changes of the membranes with different ratio of PDMS to PPO were investigated. This non-perforated structure in the membrane favored to reduce the diffusion resistance, together with the affinity of PDMS segment to alcohol during pervaporation process. Thus, the prepared PDMS-b-PPO membrane showed dramatically increased flux, in pervaporation separation of alcohol/water mixture. The flux of the PDMS-b-PPO membrane (PDMS content of 42.4%) can reach 3816.8 g/(m2·h), along with 8.53 of separation factor in pervaporation of 5 wt% alcohol/water mixture (60°C). This work may provide a new strategy to design and fabricate new copolymer membranes for improving alcohol permselective pervaporation. © BME-PT. Source

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