A composite of Fe3O4@C and multilevel porous carbon as high-rate and long-life anode materials for lithium ion batteries.

The iron oxide-based anode materials are widely studied and reported due to their abundance, low cost, high energy density and environmental friendliness for lithium ion batteries (LIBs). However, the application of LIBs is always limited by the poor rate capability and stability. In order to tackle these issues, a novel material with carbon-encapsulated Fe3O4 nanorods stuck together by multilevel porous carbon (Fe3O4@C/PC) is prepared through directly carbonizing the Fe-based metal-organic framework under a nitrogen atmosphere. This novel material shows a high specific capacity and rate performance. The initial specific capacity can reach 1789 mAh g-1 at a current density of 0.1 A g-1, and the specific capacity still remains 1105.3 mAh g-1 and 783.5 mAh g-1 after 150 cycles at the current densities of 0.1 A g-1 and 1 A g-1, respectively. Even under a current density as high as 12 A g-1, the specific capacity can achieve 309 mAh g-1 after 2000 cycles with an average attenuation rate of 0.019% per cycle. Overall, the simple strategy, low cost and high capacity can make the practical application possible.

Adsorption behavior of isocyanate/ethylenediamine tetraacetic acid-functionalized graphene oxides for Cu2+ removal.

A special adsorption of Cu2+ removal is demonstrated using specifically functionalized graphene oxide (GO)/isocyanate (MDI) composites, on which ethylenediamine tetraacetic acid (EDTA) is grafted via amidation and carbamate reaction. The structure and morphology of GO and functionalized composites (EDTA/MDI/GO) were characterized by scanning electron microscope (SEM), Fourier transform infrared spectra (FT-IR), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and Thermogravimetric analysis (TGA). This study investigated the adsorption and desorption behaviors of heavy metal cations and the effects of solution conditions such as pH on Cu2+ removal. The experimental results illustrated that after introducing EDTA and MDI into the GO, the maximum adsorption capacity reached 254.2 ± 10.4 mg/g within 180 min, obviously higher than the GO prepared without these additions (136.5 ± 7.2 mg/g). The EDTA/MDI/GO adsorption kinetics and equilibrium adsorption isotherm fitted the pseudo-second-order kinetic model (R2 = 0.995) and Langmuir isotherm model (R2 = 0.986) well, respectively. Furthermore, EDTA/MDI/GO also displayed good reusability for the efficient removal of Cu2+ after being washed with HCl, suggesting potential application in Cu2+ cleanup.

Facile self-assembly synthesis of PdPt bimetallic nanotubes with good performance for ethanol oxidation in an alkaline medium.

PdPt bimetallic nanotubes were prepared by the self-assembly of Pt and Pd on Te nanowires at room temperature. The morphologies of the as-prepared PdPt nanotubes were investigated by scanning electron microscopy and transmission electron microscopy, and the results display a large amount of PdPt bimetallic nanotubes with a diameter of 10-20 nm and a length of several micrometers. The composition and structure of the nanotubes were characterized by X-ray diffraction, high-resolution transmission electron microscopy, scanning transmission electron microscopy, and energy spectrum analysis, and the results display uniform compositional distributions of both elements (Pd and Pt). The mechanism of the formation of the nanotube structure was supposed. The electrocatalytic performance of PdPt nanotubes were studied by cyclic voltammetry and chronoamperometry. Electrochemical results show that the as-prepared PdPt nanotube catalysts have not only high activity but also good stability for ethanol oxidation in alkaline medium.

Ampere-hour-scale soft-package potassium-ion hybrid capacitors enabling 6-minute fast-charging.

Extreme fast charging of Ampere-hour (Ah)-scale electrochemical energy storage devices targeting charging times of less than 10 minutes are desired to increase widespread adoption. However, this metric is difficult to achieve in conventional Li-ion batteries due to their inherent reaction mechanism and safety hazards at high current densities. In this work, we report 1 Ah soft-package potassium-ion hybrid supercapacitors (PIHCs), which combine the merits of high-energy density of battery-type negative electrodes and high-power density of capacitor-type positive electrodes. The PIHC consists of a defect-rich, high specific surface area N-doped carbon nanotube-based positive electrode, MnO quantum dots inlaid spacing-expanded carbon nanotube-based negative electrode, carbonate-based non-aqueous electrolyte, and a binder- and current collector-free cell design. Through the optimization of the cell configuration, electrodes, and electrolyte, the full cells (1 Ah) exhibit a cell voltage up to 4.8 V, high full-cell level specific energy of 140 Wh kg-1 (based on the whole mass of device) with a full charge of 6 minutes. An 88% capacity retention after 200 cycles at 10 C (10 A) and a voltage retention of 99% at 25 ± 1 °C are also demonstrated.

Embedding FeS nanodots into carbon nanosheets to improve the electrochemical performance of anode in potassium ion batteries.

Potassium-ion batteries (PIBs) is one of the most promising alternatives for Lithium-ion batteries (LIBs) due to the low-cost and abundant potassium reserves. However, the electrochemical performances of PIBs were seriously hindered by the larger radius of potassium ions, resulting in a slow kinetic during the electrochemical reaction, especially in the PIB anodes. In the study, we propose FeS nanodots embedded S-doped porous carbon (FeS@SPC) synthesized by a simple self-template method for the storage of potassium-ions. The FeS nanodots with an average diameter of 5 nm are uniformly distributed in S-doped porous carbon nanosheets. When the FeS@SPC was used as the anode in PIBs, the unique structure of FeS@SPC can relieve the agglomeration and volume expansion of FeS effectively during the charge-discharge process. Even after 3000 cycles, the FeS nanodots are still uniformly embedded in porous carbon without agglomeration. Ascribed to the merits, the FeS@SPC exhibits a reversible capacity of 309 mAh g-1 at 0.1 A g-1 after 100 cycles and 232 mAh g-1 at 1 A g-1 after 3000 cycles. The excellent electrochemical performance of FeS@SPC is attributed to the synergistic effects of FeS nanodots and S-doped porous carbon, which facilitated the diffusion of electrolyte and accelerated the migration of potassium ions. Moreover, theoretical calculation results also suggest that the van der waals heterostructure of FeS@SPC displays higher adsorption energy for potassium ions than that of S-doped graphene, indicating the suitability of FeS@SPC for K storage.

Unsaturated fatty acid-tuned assembly of photosensitizers for enhanced photodynamic therapy via lipid peroxidation.

Photodynamic therapy (PDT) destroys tumor cells mainly through singlet oxygen (1O2) generated by light-irradiated photosensitizers (PSs). However, the fleeting half-life of 1O2 greatly impairs PDT efficacy. Herein, we propose an unreported unsaturated fatty acid (UFA)-assisted PS co-assembly strategy to address this problem. Three UFAs, namely, oleic acid (OA), linoleic acid (LA) and linolenic acid (LNA), are capable of co-assembling with 5,10,15,20-tetrakis(4-aminophenyl)porphyrin (TAPP) into uniform nanoparticles. Under irradiation, TAPP produces 1O2, which directly attacks tumor cells and simultaneously oxidizes UFAs to generate lipid hydroperoxides with sustained damage. Interestingly, the unsaturation degree of UFAs is not only related to their peroxidation rate but also has a remarkable impact on the intracellular TAPP release characteristic of the nanoparticles (NPs). The TAPP-LA NPs could release the cargo rapidly and produce the highest lipid peroxidation and reactive oxygen species levels upon irradiation. Such a unique finding sheds new light on UFA-based combination applications for enhanced photodynamic efficacy by boosting lipid peroxidation.

Facile self-templating synthesis of heteroatom-doped 3D porous carbon materials from waste biomass for supercapacitors.

Heteroatom-doped 3D porous carbon materials have been synthesized by utilizing hydroxyapatite in pig bones as a self-template and used as electrode materials for symmetric supercapacitors, which exhibit ultra-high energy density both in an aqueous electrolyte and organic electrolyte, showing great potential applications in the next generation of energy storage and conversion devices.

In Situ Self-Template Synthesis of Fe-N-Doped Double-Shelled Hollow Carbon Microspheres for Oxygen Reduction Reaction.

Herein, we reported a special Fe-N-doped double-shelled hollow carbon microsphere (Fe-N-DSC) which was prepared by a facile, in situ polymerization followed by pyrolysis. With porous ferroferric oxide (Fe3O4) hollow microspheres as the templates, where pyrrole monomers were dispersed around the outer surface and prefilled the interior space. By adding hydrochloric acid, Fe3+ ions were released to initiate polymerization of pyrrole on both the outer and inner surfaces of Fe3O4 microspheres until they were completely dissolved, resulting in the Fe-containing polypyrrole double-shelled hollow carbon microspheres (Fe-PPY-DSC). The Fe-PPY-DSC was then pyrolyzed to generate the Fe-N-DSC. The Fe3O4 hollow microspheres played trifunctional roles, i.e., the template to prepare a double-shelled hollow spherical structure, the initiator (i.e., Fe3+ ions) for the polymerization of pyrrole, and the Fe source for doping. The Fe-N-DSC exhibited a superior catalytic activity for oxygen reduction as comparable to commercial Pt/C catalysts in both alkaline and acidic media. The high catalytic performance was ascribed to the special porous double-shelled hollow spherical structure, which provided more active sites and was beneficial to a high-flux mass transportation.

Edge-Rich Quasi-Mesoporous Nitrogen-Doped Carbon Framework Derived from Palm Tree Bark Hair for Electrochemical Applications.

Biomass with abundant resources and low price is regarded as potential sources of functionalized carbon-based energy storage and conversion electrode materials. Rational construction and development of biomass-derived carbon equipped with proper morphology, structure, and composition prove the key to highly efficient utilization of advanced energy storage systems. Herein, we use palm tree bark hair as a biomass source and prepare edge/defect-rich quasi-mesoporous carbon (QMC) by a direct pyrolysis followed by NaOH etching strategy. Then, the edge-rich quasi-mesoporous nitrogen-doped carbon (QMNC) is successfully fabricated through the hydrothermal method by making use of edge/defect-rich QMC and urea as carbon precursor and nitrogen source, respectively. The microstructure and composition of the resultant carbon materials are all detected by a series of techniques. In the meantime, the influence of the etching process on the preparation and electrochemical performance of edge-rich QMNC is systematically explored. The relevant results manifest that the as-prepared edge/defect-rich QMC not only possesses edge-rich plane, much increased specific surface area (SSA), and special quasi-mesopores but also reverses good conductivity and gains sufficient defects for subsequent N doping. After introducing N atoms, the obtained edge-rich QMNC exhibits outstanding capacitive property and oxygen reduction reaction performance, which are mainly attributed to the co-effect of edge-rich plane, large SSA, suitable pore structures, and effective N doping (including high doping amount and optimized N configurations). Clearly, our work not only offers an excellent biomass-derived carbon-based electrode material but also opens a fresh avenue for the development of advanced biomass-derived carbon-based electrode materials.

A label-free electrochemical immunoassay for carcinoembryonic antigen (CEA) based on gold nanoparticles (AuNPs) and nonconductive polymer film.

A simple and sensitive label-free electrochemical immunoassay electrode for detection of carcinoembryonic antigen (CEA) has been developed. CEA antibody (CEAAb) was covalently attached on glutathione (GSH) monolayer-modified gold nanoparticle (AuNP) and the resulting CEAAb-AuNP bioconjugates were immobilized on Au electrode by electro-copolymerization with o-aminophenol (OAP). Electrochemical impedance spectroscopy and cyclic voltammetry studies demonstrate that the formation of CEA antibody-antigen complexes increases the electron transfer resistance of [Fe(CN)(6)](3-/4-) redox pair at the poly-OAP/CEAAb-AuNP/Au electrode. The use of CEA antibody-AuNP bioconjugates and poly-OAP film could enhance the sensitivity and anti-nonspecific binding of the resulting immunoassay electrode. The preliminary application of poly-OAP/CEAAb-AuNP/Au electrode for detection of CEA was also evaluated.

Platinum catalysts prepared with functional carbon nanotube defects and its improved catalytic performance for methanol oxidation.

Carbon nanotube (CNT) supported Pt nanoparticle catalysts have been prepared by spontaneous reduction of PtCl6(2-) ion as a result of direct redox reactions between PtCl6(2-) and oxygen-containing functional groups at defect sites of CNTs, which were introduced by chemical and electrochemical oxidation treatment of CNTs. The electrocatalytic properties of as-prepared Pt-CNT catalysts for methanol oxidation were investigated by chronopotentiometry and cyclic voltammetry. Compared with Pt catalysts prepared by hydrogen reduction and electrochemical deposition methods, Pt catalysts synthesized by functional CNT defects show excellent antipoisoning ability and long-term cycle stability.

Glucose biosensor based on platinum microparticles dispersed in nano-fibrous polyaniline.

A sensitive and selective amperometric glucose biosensor based on platinum microparticles dispersed in nano-fibrous polyaniline (PANI) was investigated. Poly (m-phenylenediamine) (PMPD), which was employed as an anti-interferent barrier and a protective layer to platinum microparticles, was deposited onto platinum-modified PANI in the presence of glucose oxidase. The morphology of PANI, Pt/PANI and PMPD-GOD/Pt/PANI were investigated by scanning electron microscopy. The results show that PANI has a nano-fibrous morphology. The enzyme electrode exhibits excellent response performance to glucose with linear range from 2 x 10(-6) to 12 x 10(-3) M and fast response time within 7s. Due to the selective permeability of PMPD, the enzyme electrode also shows good anti-interference to uric acid and ascorbic acid. The Michaelis-Menten constant km and the maximum current density imax of the enzyme electrode were 9.34 x 10(-3) M and 917.43 microA cm(-2), respectively. Furthermore, this glucose biosensor also has good stability and reproducibility.

Carbon nanotubes as a secondary support of a catalyst layer in a gas diffusion electrode for metal air batteries.

In this paper, we report the use of binary carbon supports (carbon nanotubes (CNTs) and active carbon) as a catalyst layer for fabricating gas diffusion electrodes. The electrocatalytic properties for the oxygen reduction reaction (ORR) were evaluated by polarization curves and electrochemical impedance spectroscopy (EIS) in an alkaline electrolyte. The binary-support electrode exhibits better performance than the single-support electrode, and the best performance is obtained when the mass ratio of carbon nanotubes and active carbon is 50:50. The results from the electrode kinetic parameters indicate that the introduction of carbon nanotubes as a secondary support provides high accessible surface area, good electronic conductivity, and fast ORR kinetics. Furthermore, the effect of CNT support on the electrocatalytic properties of Pt nanoparticles for binary-support electrodes was also investigated by different loading-reduction methods. The electrocatalytic activity of the binary-support electrodes is improved dramatically by Pt loading on CNT carbon support, even at very low Pt loading. Additionally, the EIS analysis results indicate that the process of ORR may be controlled by diffusion of oxygen in the electrode thin film for binary-support electrodes with or without Pt catalyst.

Studies of heavy metal ion adsorption on chitosan/sulfydryl-functionalized graphene oxide composites.

Chitosan/Sulfydryl-functionalized graphene oxide composite (CS/GO-SH) was successfully synthesized via covalent modification and electrostatic self-assembly. A facile diazonium chemical process was developed to fabricate sulfydryl-functionalized graphene oxide (GO-SH) by introducing sulfydryl compounds to the graphene oxide sheets (GO), and the GO-SH was used to self-assemble with chitosan via an electrostatic interaction. The chemical structure and morphology of the CS/GO-SH composite were characterized by Fourier transformed infrared, Raman spectroscopy, scanning electron microscopy, X-ray powder diffraction and thermogravimetric examination. The results indicated that the CS/GO-SH was a new type of with multifunctional groups such as -OH, -COOH, -SH and -NH2. Simultaneously, the self-assembly of chitosan with GO-SH sheets changed the blocky structure of the CS to the loosely packed structure which is analogous to graphene oxide sheets. The resulting CS/GO-SH was used as an adsorbent material for removal of Cu (II), Pb (II) and Cd (II) in single- and multi-metal ions systems. It was found that the CS/GO-SH has potential applications in fields of adsorptive materials due to its superiority of the chemical characteristic and the specific surface area.

High dispersion and electrocatalytic properties of platinum nanoparticles on graphitic carbon nanofibers (GCNFs).

Highly dispersed platinum nanoparticles were electrodeposited on graphitic carbon nanofibers (GCNFs) by cyclic voltammetry (CV) in 7.7 mM H2PtCl6+0.5 M HCl aqueous solutions. The graphitic carbon nanofibers (GCNFs) used in this paper were grown directly on a graphite disk by chemical vapor deposition (CVD). The micrographs and element composition of Pt/GCNFs/graphite electrode were characterized by scanning electron microscopy (SEM) and electron diffraction spectroscopy (EDS). The electrocatalytic properties of Pt/GCNFs/graphite electrode for methanol oxidation have been investigated by CV and excellent electrocatalytic activity can be observed even at very low platinum loading (md=8.79 microg cm(-2)). The highest mass activity (MA) for methanol oxidation reaches 323 Ag(-1) when Pt/GCNFs/graphite electrode was cycled at a sweep rate of 50 mVs(-1) by CV in 2 M CH3OH+1 M H2SO4 aqueous solutions. This may be attributed to the small particle size and high dispersion of platinum particles coated on GCNFs and shows good potential application in direct methanol fuel cell (DMFC). Additionally, the long-term cycling stability of platinum catalysts was also investigated.

Supercapacitors based on high-quality graphene scrolls.

High-quality graphene scrolls (GSS) with a unique scrolled topography are designed using a microexplosion method. Their capacitance properties are investigated by cyclic voltammetry, galvanostatic charge-discharge and electrical impedance spectroscopy. Compared with the specific capacity of 110 F g(-1) for graphene sheets, a remarkable capacity of 162.2 F g(-1) is obtained at the current density of 1.0 A g(-1) in 6 M KOH aqueous solution owing to the unique scrolled structure of GSS. The capacity value is increased by about 50% only because of the topological change of graphene sheets. Meanwhile, GSS exhibit excellent long-term cycling stability along with 96.8% retained after 1000 cycles at 1.0 A g(-1). These encouraging results indicate that GSS based on the topological structure of graphene sheets are a kind of promising material for supercapacitors.

Electrochemical behavior of L-cysteine and its detection at carbon nanotube electrode modified with platinum.

The electrochemical behavior of L-cysteine (CySH) on platinum (Pt)/carbon nanotube (CNT) electrode was investigated by cyclic voltammetry. CNTs used in this study were grown directly on graphite disk by chemical vapor deposition. Pt was electrochemically deposited on the activated CNT/graphite electrode by electroreduction of Pt(IV) complex ion on the surface of CNTs. Among graphite, CNT/graphite, and Pt/CNT electrodes, improved electrochemical behavior of CySH oxidation was found with Pt/CNT electrode. On the other hand, a sensitive CySH sensor was developed based on Pt/CNT/graphite electrode. A linear calibration curve can be observed in the range of 0.5 microM-0.1 mM. The detection limit of the Pt/CNT electrode is 0.3 microM (signal/nose=3). Effects of pH, scan rate, and interference of other oxidizable amino acids were also investigated and discussed. Additionally, the reproducibility, stability, and applicability of the Pt/CNT electrode were evaluated.