scholarly journals Layer-by-Layer Electrode Fabrication for Improved Performance of Porous Polyimide-Based Supercapacitors

Materials ◽  
2021 ◽  
Vol 15 (1) ◽  
pp. 4
Author(s):  
Niranjala Fernando ◽  
Hugo Veldhuizen ◽  
Atsushi Nagai ◽  
Sybrand Van der Zwaag ◽  
Amor Abdelkader
Keyword(s):  
Active Sites ◽  
Bottom Layer ◽  
Porous Polymer ◽  
Layer By Layer ◽  
Electrode Structure ◽  
Negative Effects ◽  
Practical Applications ◽  
Surface Areas ◽  
Redox Active ◽  
Improved Performance

Nanoporous polymers are becoming increasingly interesting materials for electrochemical applications, as their large surface areas with redox-active sites allow efficient adsorption and diffusion of ions. However, their limited electrical conductivity remains a major obstacle in practical applications. The conventional approach that alleviates this problem is the hybridisation of the polymer with carbon-based additives, but this directly prevents the utilisation of the maximum capacity of the polymers. Here, we report a layer-by-layer fabrication technique where we separated the active (porous polymer, top) layer and the conductive (carbon, bottom) layer and used these “layered” electrodes in a supercapacitor (SC). Through this approach, direct contact with the electrolyte and polymer material is greatly enhanced. With extensive electrochemical characterisation techniques, we show that the layered electrodes allowed a significant contribution of fast faradic surface reactions to the overall capacitance. The electrochemical performance of the layered-electrode SC outperformed other reported porous polymer-based devices with a specific gravimetric capacitance of 388 F·g−1 and an outstanding energy density of 65 Wh·kg−1 at a current density of 0.4 A·g−1. The device also showed outstanding cyclability with 90% of capacitance retention after 5000 cycles at 1.6 A·g−1, comparable to the reported porous polymer-based SCs. Thus, the introduction of a layered electrode structure would pave the way for more effective utilisation of porous organic polymers in future energy storage/harvesting and sensing devices by exploiting their nanoporous architecture and limiting the negative effects of the carbon/binder matrix.

Layered hydroxide/polydopamine/hyaluronic acid functionalized magnesium alloys for enhanced anticorrosion, biocompatibility and antithrombogenicity in vascular stents

2020 ◽  
Vol 34 (8) ◽  
pp. 1131-1141 ◽  
Author(s):  
Xiaojing He ◽  
Guannan Zhang ◽  
Yuliang Pei ◽  
Hongyu Zhang
Keyword(s):  
Hyaluronic Acid ◽  
Magnesium Alloys ◽  
Active Sites ◽  
Alkali Treatment ◽  
Bottom Layer ◽  
Endothelial Cell Proliferation ◽  
Layer By Layer ◽  
Vascular Stents ◽  
Strong Electrostatic Adsorption

Magnesium alloys are promising cardiovascular stent materials due to the favourable physical properties and complete biodegradability in vivo. However, the rapid degradation, poor cytocompatibility and tendency of thrombogenesis hinder practical clinical applications. In order to solve these problems, a facile and highly efficient strategy of alkali treatment combined with subsequent layer-by-layer assembly was used to fabricate a multifunctional coating. A bottom layer hydroxyl (–OH) with negative charge after alkali treatment first formed a solid bond with magnesium matrix to provide a rough outer surface for the further immobilization of functional biomolecules. Afterwards, polydopamine and hyaluronic acid were successively immobilized on alkali-treated magnesium surface via strong electrostatic adsorption and covalent bonding between carboxyl group of hyaluronic acid and amine or hydroxyl of polydopamine to form magnesium/OH/polydopamine/hyaluronic acid. Hydroxyl significantly improves the corrosion resistance while polydopamine and hyaluronic acid layers act as a further barrier to provide better anticorrosion. A balance between biocompatibility and antithrombogenicity has been achieved by adjusting the content of hyaluronic acid on polydopamine surface. The multifunctional magnesium/OH/polydopamine/hyaluronic acid coating with lower hyaluronic acid concentrations expose more active sites of polydopamine molecules to promote endothelial cell proliferation while retaining the intrinsic antithrombogenic function of hyaluronic acid to offer a potential application for vascular stents.

Hierarchical Porous Covalent organic framework/graphene aerogel electrode for High-Performance Supercapacitors

2021 ◽  
Author(s):  
Ning An ◽  
Zhen Guo ◽  
Jiao Xin ◽  
Yuan-Yuan He ◽  
Ke-Feng Xie ◽  
...  
Keyword(s):  
Energy Storage ◽  
Active Sites ◽  
High Performance ◽  
Energy Storage Materials ◽  
Covalent Organic Frameworks ◽  
Graphene Aerogel ◽  
Covalent Organic Framework ◽  
Surface Areas ◽  
Redox Active ◽  
Hierarchical Porous

Redox-active covalent organic frameworks (COFs) are an emerging class of energy storage materials due to their notably abundant active sites, well-defined channels and highly surface areas. However, their poor electrical...

scholarly journals Simultaneous Adsorption and Reduction of Cr(VI) to Cr(III) in Aqueous Solution Using Nitrogen-Rich Aminal Linked Porous Organic Polymers

2021 ◽  
Vol 13 (2) ◽  
pp. 923
Author(s):  
Muhammad A. Sabri ◽  
Ziad Sara ◽  
Mohammad H. Al-Sayah ◽  
Taleb H. Ibrahim ◽  
Mustafa I. Khamis ◽  
...  
Keyword(s):  
Active Sites ◽  
Condensation Reaction ◽  
Significant Loss ◽  
Single Step ◽  
High Porosity ◽  
Organic Polymers ◽  
Porous Organic Polymers ◽  
One Pot ◽  
Surface Areas ◽  
Redox Active

Two novel nitrogen-rich aminal linked porous organic polymers, NRAPOP-O and NRAPOP-S, have been prepared using a single step-one pot Schiff-base condensation reaction of 9,10-bis-(4,6-diamino-S-triazin-2-yl)benzene and 2-furaldehyde or 2-thiophenecarboxaldehyde, respectively. The two polymers show excellent thermal and physiochemical stabilities and possess high porosity with Brunauer–Emmett–Teller (BET) surface areas of 692 and 803 m2 g−1 for NRAPOP-O and NRAPOP-S, respectively. Because of such porosity, attractive chemical and physical properties, and the availability of redox-active sites and physical environment, the NRAPOPs were able to effectively remove Cr(VI) from solution, reduce it to Cr(III), and simultaneously release it into the solution. The efficiency of the adsorption process was assessed under various influencing factors such as pH, contact time, polymer dosage, and initial concentration of Cr(VI). At the optimum conditions, 100% removal of Cr(VI) was achieved, with simultaneous reduction and release of Cr(III) by NRAPOP-O with 80% efficiency. Moreover, the polymers can be easily regenerated by the addition of reducing agents such as hydrazine without significant loss in the detoxication of Cr(VI).

scholarly journals Research on Improving the Durability of Bridge Pavement Using a High-Modulus Asphalt Mixture

Materials ◽  
2021 ◽  
Vol 14 (6) ◽  
pp. 1449
Author(s):  
Wenfeng Wang ◽  
Shaochan Duan ◽  
Haoran Zhu
Keyword(s):  
Construction Industry ◽  
Mechanical Response ◽  
Design Method ◽  
Asphalt Mixture ◽  
Field Tests ◽  
Bottom Layer ◽  
High Modulus ◽  
Practical Applications ◽  
Depth Prediction ◽  
Pavement Structure

In order to improve the durability of the asphalt pavement on a cement concrete bridge, this study investigated the effect of the modulus of the asphalt mixture at the bottom layer on the mechanical response of bridge pavement, along with a type of emerging bridge pavement structure. In addition, the design method and pavement performance of a high-modulus asphalt mixture were investigated using laboratory and field tests, and the life expectancy of the deck pavement structure was predicted based on the rutting deformation. The results showed that the application of a high-modulus asphalt mixture as the bottom asphalt layer decreased the stress level of the pavement structure. The new high-modulus asphalt mixture displayed excellent comprehensive performance, i.e., the dynamic stability reached 9632 times/mm and the fatigue life reached 1.65 million cycles. Based on the rutting depth prediction, using high-modulus mixtures for the bridge pavement prolonged the service life from the original 5 years to 10 years, which significantly enhanced the durability of the pavement structure. These research results could be of potential interest for practical applications in the construction industry.

scholarly journals Conjugate of Thiol and Guanidyl Units with Oligoethylene Glycol Linkage for Manipulation of Oxidative Protein Folding

Molecules ◽  
2021 ◽  
Vol 26 (4) ◽  
pp. 879
Author(s):  
Shunsuke Okada ◽  
Motonori Matsusaki ◽  
Masaki Okumura ◽  
Takahiro Muraoka
Keyword(s):  
Protein Folding ◽  
Active Sites ◽  
Biological Process ◽  
Thiol Group ◽  
Native Conformation ◽  
Thiol Compounds ◽  
Oxidative Protein Folding ◽  
Redox Active ◽  
A Cell ◽  
Protein Disulfide

Oxidative protein folding is a biological process to obtain a native conformation of a protein through disulfide-bond formation between cysteine residues. In a cell, disulfide-catalysts such as protein disulfide isomerase promote the oxidative protein folding. Inspired by the active sites of the disulfide-catalysts, synthetic redox-active thiol compounds have been developed, which have shown significant promotion of the folding processes. In our previous study, coupling effects of a thiol group and guanidyl unit on the folding promotion were reported. Herein, we investigated the influences of a spacer between the thiol group and guanidyl unit. A conjugate between thiol and guanidyl units with a diethylene glycol spacer (GdnDEG-SH) showed lower folding promotion effect compared to the thiol–guanidyl conjugate without the spacer (GdnSH). Lower acidity and a more reductive property of the thiol group of GdnDEG-SH compared to those of GdnSH likely resulted in the reduced efficiency of the folding promotion. Thus, the spacer between the thiol and guanidyl groups is critical for the promotion of oxidative protein folding.

scholarly journals Synthesis, Characterization and Photocatalytic Activity of Nanocrystalline First Transition-Metal (Ti, Mn, Co, Ni and Zn) Oxisde Nanofibers by Electrospinning

2018 ◽  
Vol 9 (1) ◽  
pp. 8 ◽  
Author(s):  
Yu Chen ◽  
Weipeng Lu ◽  
Yanchuan Guo ◽  
Yi Zhu ◽  
Haojun Lu ◽  
...  
Keyword(s):  
Electron Microscope ◽  
Transition Metal ◽  
Metal Oxide ◽  
Specific Surface ◽  
Three Dimensional ◽  
Photogenerated Electron ◽  
Practical Applications ◽  
Surface Areas ◽  
Tio2 Nanofiber ◽  
Transmission Electron

In this work, five nanocrystalline first transition-metal (Ti, Mn, Co, Ni and Zn) oxide nanofibers were prepared by electrospinning and controlled calcination. The morphology, crystal structure, pore size distribution and specific surface area were systematically studied by scanning electron microscope (SEM), transmission electron microscope (TEM), surface and pore analysis, and thermo gravimetric analyzer (TGA). The results reveal that the obtained nanofibers have a continuously twisted three-dimensional scaffold structure and are composed of neat nanocrystals with a necklace-like arrangement. All the samples possess high specific surface areas, which follow the order of NiO nanofiber (393.645 m2/g) > TiO2 nanofiber (121.445 m2/g) > ZnO nanofiber (57.219 m2/g) > Co3O4 nanofiber (52.717 m2/g) > Mn2O3 nanofiber (18.600 m2/g). Moreover, the photocatalytic degradation of methylene blue (MB) in aqueous solution was investigated in detail by employing the five kinds of metal oxide nanofibers as photocatalysts under ultraviolet (UV) irradiation separately. The results show that ZnO, TiO2 and NiO nanofibers exhibit excellent photocatalytic efficiency and high cycling ability to MB, which may be ascribed to unique porous structures and the highly efficient separation of photogenerated electron-hole pairs. In brief, this paper aims to provide a feasible approach to achieve five first transition-metal oxide nanofibers with excellent performance, which is important for practical applications.

scholarly journals Bilayer graphene oxide membranes for a wearable hemodialyzer

2020 ◽  
Author(s):  
Richard P. Rode ◽  
Henry H. Chung ◽  
Hayley N. Miller ◽  
Thomas R. Gaborski ◽  
Saeed Moghaddam
Keyword(s):  
Graphene Oxide ◽  
Cytochrome C ◽  
Self Assembly ◽  
Bilayer Membrane ◽  
Blood Proteins ◽  
High Mechanical Strength ◽  
Practical Applications ◽  
New Process ◽  
Improved Performance ◽  
Oxide Membranes

2D nanomaterials have long been considered for development of ultra-high throughput membranes, due to their atomically thin nature and high mechanical strength. However, current processes have yet to yield a viable membrane for practical applications due to the lack of scalability and substantially improved performance over existing membranes. Herein, a graphene oxide (GO) bilayer membrane with a permeability of 1562 mL/hr.mmHg.m2, two orders of magnitude higher than existing nanofiltration membranes, and a tight molecular weight cut-off (MWCO) is presented. To build such a membrane, we have developed a new process involving self-assembly and optimization of GO nanoplatelets physicochemical properties. The process produced a highly organized mosaic of nanoplatelets enabling ultra-high permeability and selectivity with only three layers of GO. Performance of the membrane has been evaluated in a simulated hemodialysis application, where it presents a great value proposition. The membrane has a precise molecular cut-off size of 5 nm, adjusted using a molecular interlinker, designed to prevent loss of critical blood proteins. Urea, cytochrome-c, and albumin are used as representative test molecules. Urea and cytochrome-c sieving coefficients of 0.5 and 0.4 were achieved under physiological pressure conditions, while retaining 99% of albumin. Hemolysis, complement activation, and coagulation studies exhibit a performance on par or superior to the existing hemodialyzer materials.

scholarly journals Atomic Engineering Bifunctional Niobium (V)-based Heterostructure Nanosheet for High Efficiency Lean-Electrolyte Lithium-Sulfur Full Batteries

2021 ◽  
Author(s):  
Haodong Shi ◽  
Jieqiong Qin ◽  
Pengfei Lu ◽  
Cong Dong ◽  
Pratteek Das ◽  
...  
Keyword(s):  
High Efficiency ◽  
Electrode Structure ◽  
Practical Applications ◽  
Dual Functional ◽  
Redox Kinetics ◽  
Minimum Capacity ◽  
Li Ion ◽  
Positive Capacity ◽  
Areal Capacity ◽  
Lithium Sulfur

Abstract High-efficiency lithium-sulfur (Li-S) batteries depend on advanced electrode structure that can attain high sulfur utilization at lean-electrolyte and limited lithium. Herein, a twinborn holey Nb4N5-Nb2O5 heterostructure is designed as a dual-functional host for both redox-kinetics-accelerated sulfur cathode and dendrite-inhibited Li anode simultaneously for long-cycling and lean-electrolyte Li-S full batteries. Benefiting from the accelerative polysulfides anchoring-diffusion converting efficiency and electronic-conducting properties of Nb4N5-Nb2O5, polysulfide-shutting is significantly alleviated. Meanwhile, the lithiophilic nature of holey Nb4N5-Nb2O5 is applied as ion-redistributor for homogeneous Li-ion deposition. Taking advantage of these merits, the Li-S full batteries present the excellent electrochemical properties, including a minimum capacity decay of 0.025% per cycle, and a high areal-capacity of 5.0 mAh cm− 2 at sulfur loading of 6.9 mg cm− 2, corresponding to negative to positive capacity ratio (2.4:1) and electrolyte to sulfur ratio (5.1 µl mg− 1). Therefore, this work opens a new avenue for boosting high-performances Li-S batteries towards practical applications.

scholarly journals Microclimate Evaluation of the Hradec Králové City using HUMIDEX

2017 ◽  
Vol 47 (3) ◽  
pp. 231-246 ◽  
Author(s):  
Jaroslav Rožnovský ◽  
Tomáš Litschmann ◽  
Hana Středová ◽  
Tomáš Středa ◽  
Petr Salaš ◽  
...  
Keyword(s):  
Radiation Balance ◽  
Negative Effects ◽  
Environment Analysis ◽  
Surface Areas ◽  
Air Temperatures ◽  
Green Areas ◽  
Urban Heat ◽  
Surrounding Landscape ◽  
The City ◽  
Very High

Abstract Urban environment differs from the surrounding landscape in terms of the values of meteorological parameters. This is often referred to as the urban heat island (UHI), which in simple terms means higher air temperatures in cities. The cause of these changes lies in the different active surfaces in cities, which subsequently results in a different radiation balance. The higher temperatures, however, also affect the living conditions in the city and during very high temperature periods can have negative effects on the health of the city inhabitants. The results presented in this paper are based on measurements taken over several years at locations near Hradec Králové, which is surrounded by different surface areas. Environment analysis was performed using the Humidex index. The obtained results show that replacing green areas with built-up areas affects temperatures in the city, when air temperatures are very high they significantly increase the discomfort of the inhabitants. Differences in the frequency of discomfort levels are observed especially during periods of high temperatures, at lower temperatures these differences are not significant. Higher frequencies of discomfort are observed at locations with artificial surfaces (asphalt, cobblestones, concrete) and in closed spaces. In contrast, locations with lots of green areas almost always have the value of this index lower or more balanced. The results should therefore be a valid argument for maintaining and extending green areas in cities.

Sign in / Sign up

Export Citation Format

Share Document