High Density Single Fe Atoms on Mesoporous N-Doped Carbons: Noble Metal-Free Electrocatalysts for Oxygen Reduction Reaction in Acidic and Alkaline Media.

It remains a challenge to develop efficient noble metal-free electrocatalysts for the oxygen reduction reaction (ORR) in various renewable energy systems. Single atom catalysts have recently drawn great attention as promising candidates both due to their high activity and their utmost atom utilization for electrocatalytic ORR. Herein, the synthesis of an efficient ORR electrocatalyst that is composed of N-doped mesoporous carbon and a high density (4.05 wt%) of single Fe atoms via pyrolysis Fe-conjugated polymer is reported. Benefiting from the abundant atomic Fe-N4 sites on its conductive, mesoporous carbon structures, this material exhibits an excellent electrocatalytic activity for ORR, with positive onset potentials of 0.93 and 0.98 V in acidic and alkaline media, respectively. Its electrocatalytic performance for ORR is also comparable to that of Pt/C (20 wt%) in both media. Furthermore, it electrocatalyzes the reaction almost fully to H2 O (or barely to H2 O2 ). Additionally, it is durable and tolerates the methanol crossover reaction well. Furthermore, a proton exchange membrane fuel cell and a zinc-air battery assembled using it on their cathode deliver high maximum power densities (320 and 91 mW cm-2 , respectively). Density functional theory calculation reveals that the material's decent electrocatalytic performance for ORR is due to its atomically dispersed Fe-N4 sites.

Transparent Oil-Water Separating Hydrophobic Sponge Prepared from a Pickering High Internal Phase Emulsion Stabilized by Octadecyltrichlorosilane Grafting Carbon Nanotubes.

Increasingly, oil spills and industrial discharges are wreaking havoc on the water environment; in order to efficiently separate oil and water from sewage containing oil or organic solvents, a novel porous polymer (P(EHA-co-BA)) was prepared by Pickering high internal phase emulsion (HIPE) template method. To obtain polyHIPE with better oil/water separation capacities, octadecyltrichlorosilane (OTS)-modified carbon nanotubes (CNTs) and surfactants were used as costabilizers for HIPE, which improved the stability of HIPE as well as the mechanical properties and the separation efficiency of polyHIPE. In the presence of 1 wt % OTS-CNT adding in the oil phase, 1%OTS-CNT polyHIPE has high porosity (92.21%), favorable hydrophobicity (a water contact angle of 128°), and excellent mechanical properties. As a result, 1%OTS-CNT polyHIPE has high absorption of oils and oily solvents, e.g., dichloromethane up to 36 g/g, and maintains an absorption efficiency of >97% after 20 reapplications. In the formulation of polyHIPE, cinnamaldehyde (CA) has been added to provide superior antibacterial properties against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). It appears that the novel polyHIPE proposed in this work is a reusable antibacterial porous polymer with promising applications for oil-water separation.

MOF@Polydopamine-incorporated membrane with high permeability and mechanical property for efficient fouling-resistant and oil/water separation.

Metal organic frameworks (MOFs) have demonstrated great potential for their favorable impacts on the performance of water treatment membranes. Herein, the novel nanoparticles based on both nanoporous MOFs and organic PDA layer was exploited as a novel dopant for the fabrication of PES ultrafiltration (UF) membranes. The PDA was synthesized via oxidative self-polymerization under alkaline conditions and formed adhesive coatings on dispersed MOF. The properties of resulting membranes on the porosity, membrane morphology, hydrophilicity, permeability and anti-fouling performance were adequately investigated. The membranes incorporated with MOF@PDA exhibited exceptionally high permeability (209.02 L m-2·h-1), which is approximately 6 times higher than that of the pure PES membrane, and high BSA rejection (99.12%). Notably, the mechanical property and hydrophilicity of the PES membrane were both enhanced by MOF@PDA, and it has been demonstrated that greater hydrophilicity prevents fouling under practical conditions, which results in significant improvements in flux recovery ratio (FRR) (82%). In addition, the modified PES membranes were used to purify the oil/water emulsion, and the results indicates that the membranes have high permeability and rejection of oil/water emulsion, showing its great promise in practical oily sewage remediation.

Amphiphilic Grafted Polymers Based on Citric Acid and Aniline Used to Enhance the Antifouling and Permeability Properties of PES Membranes.

Water treatment technology based on ultrafiltration (UF) faces the problem of severe membrane fouling due to its inherent hydrophobicity. The use of amphiphilic polymers that possess both hydrophobic and hydrophilic chain segments can be advantageous for the hydrophilic modification of UF membranes due to their excellent combination in the membrane matrix. In the present study, we examined a novel amphiphilic CA-g-AN material, constructed by grafting citric acid (CA) to aniline (AN), as a modified material to improve the hydrophilicity of a PES membrane. This material was more compatible with the polymer membrane matrix than a pure hydrophilic modified material. The polyethersulfone (PES) membranes modified by amphiphilic CA-g-AN demonstrated a higher water flux (290.13 L·m-2·h-1), which was more than eight times higher than that of the pure PES membrane. Furthermore, the flux recovery ratio (FRR) of the modified membrane could reach 83.24% and the value of the water contact angle (WCA) was 76.43°, demonstrating the enhanced hydrophilicity and antifouling ability of the modified membranes. With this study, we aimed to develop a new amphiphilic polymer to improve the antifouling property and permeability of polymer-based UF membranes to remove organic pollutants from water.

Synergistic Antimicrobial Glycyrrhizic Acid-Based Functional Biosensing Composite for Sensitive Glucose Monitoring and Collaborative Wound Healing.

High glucose blood and bacterial infection remain major issues for the slow healing of diabetic wounds, so developing functional biosensing composite with excellent antibacterial and remarkable glucose response sensitivity is necessary and prospective. Herein, by in situ synthesis AgNPs on the surface of self-prepared PTIGA elastomers, PTIGA-AgNPs conductive composites are obtained with efficient synergistic antibacterial effect, excellent mechanical and self-healing properties. The strain of the composites can reach 1800%, and its self-healing efficiency exceeds 90% at 60 °C within 8 h. Both elastomers and composites represent excellent biocompatibility and the antibacterial rate against E. coli and S. aureus exceeded 90%. Moreover, the biosensor assembled from the conductive composites exhibits excellent glucose response sensitivity and stability, with a sensitivity coefficient of 0.518 mA mm-1 in the range of 0.2-3.6 × 10-3 m glucose concentration, as well as a low detection limit of 0.08 × 10-3 m. Furthermore, based on the remarkable antibacterial performance and bioactivity derived from GA, the composites reduce the expression of pro-inflammatory factors and promote the production of anti-inflammatory factors, and effectively promote the regeneration of skin and granulation tissue of wounds in a diabetic full-thickness skin defect model, demonstrating the enormous therapeutic potential in diabetic wound healing.

A sensitive non-enzymatic dual-conductive biosensor for continuous glucose monitoring.

BACKGROUND: Diabetes and diabetic wound management have always been urgent issues for global healthcare. In the demand for blood glucose monitoring and wound management, phenylboronic acid (PBA)-based glucose biosensors are effective assistance due to their excellent glucose specificity, high sensitivity, and response stability. Nevertheless, PBA-based glucose biosensors still have challenges in terms of wide linearity and large deformation requirements. Therefore, it is necessary to develop PBA-based glucose biosensors with satisfactory mechanical properties, high response sensitivity, excellent stability, and wide linearity. RESULTS: In this work, a glucose-responsive PBA-based biosensor was successfully synthesized for the first time. The sensor materials exhibited excellent mechanical properties with an elongation at break reached up to 1000%, and the healing efficiency was over 90% within 30 min at 45 °C. Furthermore, the biosensor exhibited exceptional electromechanical responsiveness, stability, high sensitivity, and wide linearity due to the specificity of phenylboronic acid to glucose and the construction of a special HCNT/PEDOT:PSS dual conductive structure. In addition, the assembled biosensor displayed remarkable glucose, pH and temperature responses, exhibiting a linear response to glucose concentration range from 0.20 mM to 2.0 mM, with a sensitivity coefficient of 47.11 mA mM-1 and regression coefficient of 0.942. Moreover, the sensor materials showed satisfactory cytocompatibility, hemocompatibility, and antibacterial properties against Escherichia coli and Staphylococcus aureus. SIGNIFICANCE: For the first time, a dual conductive structural glucose biosensor based on PBA-based copolymer was synthesized. In addition to excellent glucose sensitivity and response stability, the biosensor has a wide linearity range, excellent self-healing property, and satisfactory mechanical performance. As a promising substitute for non-enzymatic glucose biosensors, this new material with special structure and characteristics would also be beneficial to wound management in diabetic patients.

Rapid and Facile Synthesis of High-Performance Silver Nanowires by A Halide-Mediated, Modified Polyol Method for Transparent Conductive Films.

Silver nanowires are receiving increasing attention as a kind of prospective transparent and conductive material. Here, we successfully synthesized high-performance silver nanowires with a significantly decreased reaction time by a modified polyol method. The synthesis process involved the addition of halides, including NaCl and NaBr, to control the release rate of Ag+ ions, as Cl- and Br- ions react with Ag+ ions to form AgCl and AgBr with different solubilities. As a result, Ag+ ions could be slowly released by graded dissolution, and the formation of silver nanowires was promoted. The results showed that the concentration of the added halides played an important role in the morphology of the final product. High-quality silver nanowires with an average diameter of 70 nm and average length of 21 µm were obtained by optimizing the reaction parameters. Afterwards, a simple silver nanowire coating was applied in order to fabricate the transparent conductive films. The film that was based on the silver nanowires provided a transmittance of 91.2% at the 550 nm light wavelength and a sheet resistance of about 78.5 Ω·sq-1, which is promising for applications in flexible and transparent optoelectronic devices.

Effect of CeH2.73-CeO2 Composites on the Desorption Properties of Mg2NiH4.

A series of CeH2.73/CeO2 composites with different ratios of hydride and oxide phases are prepared from the pure cerium hydride via oxidation treatments in the air at room temperature, and they are subsequently doped into Mg2NiH4 by ball milling. The desorption properties of the as-prepared Mg2NiH4+CeH2.73/CeO2 composites are studied by thermogravimetry and differential scanning calorimetery. Microstructures are studied by scanning electron microscopy and transmission electron microscopy, and the phase transitions during dehydrogenation are analyzed through in situ X-ray diffraction. Results show that the initial dehydrogenation temperature and activation energy of Mg2NiH4 are maximally reduced by doping the CeH2.73/CeO2 composite with the same molar ratio of cerium hydride and oxide. In this case, the CeH2.73/CeO2 composite has the largest density of interface among them, and the hydrogen release effect at the interface between cerium hydride and oxide plays an efficient catalytic role in enhancing the hydrogen desorption properties of Mg2NiH4.

Corrigendum to "Synthesis, Morphology, and Hydrogen Absorption Properties of TiVMn and TiCrMn Nanoalloys with a FCC Structure".

[This corrects the article DOI: 10.1155/2018/5906473.].

Carbon-Based Nanomaterials as Sustainable Noble-Metal-Free Electrocatalysts.

Nowadays, due to the worldwide growth demand of energy, over consumption of fossil fuel as well as their accompanying increased negative environmental impacts, the development of renewable energy systems, such as fuel cells and water electrolyzers, is becoming one of the "holy grail" for researchers. However, their large-scale applications have been severely limited by precious and unsustainable noble-metal electrocatalysts. Hence, it is highly desirable to develop robust electrocatalysts composed exclusively of low-cost and earth-abundant elements, to reduce or replace expensive and scarce noble-metals. Carbon-based nanomaterials, including heteroatoms-doped carbons and carbon-encapsulated metal materials, have recently attracted great interests because they show remarkable electrocatalytic performance and long-term stability for energy-related reactions, such as oxygen reduction reaction (ORR), hydrogen and oxygen evolution reactions (OER), hydrazine oxidation reaction (HzOR), etc. This review summarizes the recent progress in heteroatoms-doped carbon and carbon-encapsulated metal materials, highlighting the promise as cost-efficient electrocatalysts. Finally, a prospective on the future development of these promising materials is offered.

In Situ Growth of a High-Performance All-Solid-State Electrode for Flexible Supercapacitors Based on a PANI/CNT/EVA Composite.

For the development of light, flexible, and wearable electronic devices, it is crucial to develop energy storage components combining high capacity and flexibility. Herein, an all-solid-state supercapacitor is prepared through an in situ growth method. The electrode contains polyaniline deposited on a carbon nanotube and a poly (ethylene-co-vinyl acetate) film. The hybrid electrode exhibits excellent mechanical and electrochemical performance. The optimized few-layer polyaniline wrapping layer provides a conductive network that effectively enhances the cycling stability, as 66.4% of the starting capacitance is maintained after 3000 charge/discharge cycles. Furthermore, the polyaniline (PANI)-50 displays the highest areal energy density of 83.6 mWh·cm-2, with an areal power density of 1000 mW·cm-2, and a high areal capacity of 620 mF cm-2. The assembled device delivers a high areal capacity (192.3 mF·cm-2) at the current density of 0.1 mA·cm-2, a high areal energy (26.7 mWh·cm-2) at the power density of 100 mW·cm-2, and shows no significant decrease in the performance with a bending angle of 180°. This unique flexible supercapacitor thus exhibits great potential for wearable electronics.

Direct Writing Supercapacitors Using a Carbon Nanotube/Ag Nanoparticle-Based Ink on Cellulose Acetate Membrane Paper.

In this work, we present a cellulose acetate membrane flexible supercapacitor prepared through a direct writing method. A carbon nanotube (CNT) and silver (Ag) nanoparticle were prepared into ink for direct writing. The composite electrode displayed excellent electrochemical and mechanical electrochemical performance. Furthermore, the CNT-Ag displayed the highest areal capacity of 72.8 F/cm3. The assembled device delivered a high areal capacity (17.68 F/cm3) at a current density of 0.5 mA/cm2, a high areal energy (9.08-5.87 mWh/cm3) at a power density of 1.18-0.22 W/cm3, and showed no significant decrease in performance with a bending angle of 180°. The as-fabricated CNT/Ag electrodes exhibited good long-term cycling stability after 1000 time cycles with 75.92% capacitance retention. The direct writing was a simple, cost-effective, fast, and non-contact deposition method. This method has been used in current printed electronic devices and has potential applications in energy storage.

Synthesis, Morphology, and Hydrogen Absorption Properties of TiVMn and TiCrMn Nanoalloys with a FCC Structure.

TiVMn and TiCrMn alloys are promising hydrogen storage materials for onboard application due to their high hydrogen absorption content. However, the traditional synthesis method of melting and continuous necessary heat treatment and activation process are energy- and time-consuming. There is rarely any report on kinetics improvement and nanoprocessing in TiVMn- and TiCrMn-based alloys. Here, through ball milling with carbon black as additive, we synthesized face-centered cubic (FCC) structure TiVMn- and TiCrMn-based nanoalloys with mean particle sizes of around a few to tens of µm and with the crystallite size just 10 to 13 nm. Differential scanning calorimetry (DSC) measurements under hydrogen atmosphere of the two obtained TiVMn and TiCrMn nanoalloys show much enhancement on the hydrogen absorption performance. The mechanism of the property improvement and the difference in the two samples were discussed from microstructure and morphology aspects. The study here demonstrates a new potential methodology for development of next-generation hydrogen absorption materials.

Advanced SEM and TEM Techniques Applied in Mg-Based Hydrogen Storage Research.

Mg-based materials are regarded as one of the most promising candidates for hydrogen storage. In order to clarify the relationship between the structures and properties as well as to understand the reaction and formation mechanisms, it is beneficial to obtain useful information about the size, morphology, and microstructure of the studied materials. Herein, the use of scanning electron microscopy (SEM) and transmission electron microscopy (TEM) techniques for the representation of Mg-based hydrogen storage materials is described. The basic principles of SEM and TEM are presented and the characterizations of the size, morphology observation, phase and composition determination, and formation and reaction mechanisms clarification of Mg-based hydrogen storage materials are discussed. The applications of advanced SEM and TEM play significant roles in the research and development of the next-generation hydrogen storage materials.

Ti-Based Biomedical Material Modified with TiOx/TiNx Duplex Bioactivity Film via Micro-Arc Oxidation and Nitrogen Ion Implantation.

Titanium (Ti) and Ti-based alloy are widely used in the biomedical field owing to their excellent mechanical compatibility and biocompatibility. However, the bioinert bioactivity and biotribological properties of titanium limit its clinical application in implants. In order to improve the biocompatibility of titanium, we modified its surface with TiOx/TiNx duplex composite films using a new method via micro-arc oxidation (MAO) and nitrogen ion implantation (NII) treatment. The structural characterization results revealed that the modified film was constructed by nanoarrays composed of TiOx/TiNx composite nanostitches with a size of 20~40 nm. Meanwhile, comparing this with pure Ti, the friction property, wear resistance, and bioactivity were significantly improved based on biotribological results and in vitro bioactivity tests.

Metal Hydride Nanoparticles with Ultrahigh Structural Stability and Hydrogen Storage Activity Derived from Microencapsulated Nanoconfinement.

Metal hydrides (MHs) have recently been designed for hydrogen sensors, switchable mirrors, rechargeable batteries, and other energy-storage and conversion-related applications. The demands of MHs, particular fast hydrogen absorption/desorption kinetics, have brought their sizes to nanoscale. However, the nanostructured MHs generally suffer from surface passivation and low aggregation-resisting structural stability upon absorption/desorption. This study reports a novel strategy named microencapsulated nanoconfinement to realize local synthesis of nano-MHs, which possess ultrahigh structural stability and superior desorption kinetics. Monodispersed Mg2 NiH4 single crystal nanoparticles (NPs) are in situ encapsulated on the surface of graphene sheets (GS) through facile gas-solid reactions. This well-defined MgO coating layer with a thickness of ≈3 nm efficiently separates the NPs from each other to prevent aggregation during hydrogen absorption/desorption cycles, leading to excellent thermal and mechanical stability. More interestingly, the MgO layer shows superior gas-selective permeability to prevent further oxidation of Mg2 NiH4 meanwhile accessible for hydrogen absorption/desorption. As a result, an extremely low activation energy (31.2 kJ mol-1 ) for the dehydrogenation reaction is achieved. This study provides alternative insights into designing nanosized MHs with both excellent hydrogen storage activity and thermal/mechanical stability exempting surface modification by agents.

Improvement of hydrogen storage property of three-component Mg(NH2)2-LiNH2-LiH composites by additives.

The three-component Mg(NH2)2-LiNH2-4LiH composite reversibly stores hydrogen exceeding 5 wt% at a temperature as low as 150 °C. In this work, a number of additives such as CeF4, CeO2, TiCl3, TiH2, NaH, KBH4 and KH are added to the Mg(NH2)2-LiNH2-4LiH composite in order to improve its kinetics, thermodynamics and cycling properties. Addition of 3 wt% of KH reduces the dehydrogenation onset temperature of the Mg(NH2)2-LiNH2-4LiH composite to below 90 °C without emission of NH3 during the whole dehydrogenation process up to 450 °C. Moreover, the dehydrogenation kinetics and cycling ability are remarkably enhanced upon KH-addition. The reaction model of the Mg(NH2)2-LiNH2-4LiH composite is altered upon KH-addition with the active molecule density improved by about 200 times. In addition, by optimization of the ratio of Mg2+ to Li+ in the Mg(NH2)2-LiNH2-LiH system, several novel composites, e.g., Mg(NH2)2-2LiNH2-5.9LiH-0.1KH and Mg(NH2)2-LiNH2-5.9LiH-0.1KH, with the hydrogen storage capacity exceeding 6 wt% without emission of NH3 below 250 °C are developed. Our study demonstrates that there are various undiscovered candidates with promising hydrogen storage properties in the three-component Li-Mg-N-H system.