Search

Tailoring of battery-type NiCo 2 O 4 with carbon-based materials for supercapacitors usually involves several steps, which require prolonged syntheses at high temperatures. Here, a facile one-step strategy is presented for the fabrication of a binder-free composite, made of NiO x decorated multi-walled carbon nanotubes (CNTs) and NiCo 2 O 4 nanoparticles on nickel foam to form a stable supercapacitor with high specific capacity. The process is based on the electrophoretic co-deposition of carboxylated-CNTs and NiCo 2 O 4 NPs, which were positively charged using Ni2+. The latter played a double role by stabilizing the nanomaterials and improving the electrochemical performance by decorating the nanomaterials with NiO x species. The well-dispersed NiCo 2 O 4 NPs in the highly conductive porous matrix of CNTs provide efficient electron transfer, high surface area and superior electrochemical performance, such as high charge storage, high rate delivery and good cycling stability. The nanocomposite film exhibited high specific capacitance of 1363 F gr−1 at 2 A gr−1, while retaining 82% of the capacitance at higher current density (20 A gr−1). The straightforward fabrication process and the excellent electrochemical activity are of generic nature and can be applied for assembling other well-structured carbon-based composites. [ABSTRACT FROM AUTHOR]

Nb2O5@carbon/reduced graphene oxide (M-Nb2O5@C/rGO) composites are fabricated by annealing the precursor of graphene oxide supported Nb-based metal organic frameworks for the first time. The lithium ion capacitor using M-Nb2O5@C/rGO as the anode and activated carbon as the cathode delivers a high energy density of 71.5 W h kg−1 and excellent cycling stability. [ABSTRACT FROM AUTHOR]

Abstract The sensing performance of a Langmuir-Blodgett monolayer was significantly improved by controlling the film organization at the air-water interface. Cellulose acetate (CA) and 4-tert-butylcalix [6]arene (calix) were co-spread and formed a Langmuir film, which was efficiently transferred onto a preoxidized gold electrode, Au ox. The modified gold electrode was applied as a fast, highly sensitive electrochemical sensing platform for the quantitative determination of a model molecule, dopamine (DA). The modified gold electrode, CA-calix/Au ox , demonstrated better recognition and sensing ability towards dopamine as compared with electrodes modified by a single component. Under the optimized conditions, the reduction peak currents at the CA-calix/Au ox increased linearly within the concentration range of dopamine from 5 to 100 and 100–7500 nM, and exhibited a very low limit of detection (LOD) of 2.54 nM (S/N = 3). These results suggest a simple, superior and efficient approach for the controllable rearrangement of Langmuir-Blodgett monolayers on a molecular level. The electroanalytical performance was optimized from the perspective of the electrode-electrolyte interface. Graphical abstract Image 1 Highlights • A mixed Langmuir layer composed of cellulose acetate, and the selectivity factor, calixarene, were co-spread at the air-water interface. • The Langmuir film was transferred onto a solid gold electrode and used as a means of electrochemically detecting dopamine. • The Langmuir-Blodgett based interface was carefully studied and exhibits superior electrochemical performance for the detection of dopamine. [ABSTRACT FROM AUTHOR]

Abstract Despite many efforts devoted to explore novel electrode materials for lithium ion hybrid supercapacitors, the obtainable long-life cycling of existing anode materials are still inadequate for promising applications. This report demonstrates a new nanocomposite with TiNb 2 O 7 network nanostructure in situ anchored onto the holey graphene, which is designed as anode material for lithium ion hybrid supercapacitors. Impressively, electrochemical analyses show that the good rate performance (capacity retention of 73.5% from 0.05 to 5 A g−1) and long cycle life up to 1000 cycles at 1 A g−1 (a capacity retention of 91.5%) are attained. Furthermore, the lithium ion hybrid supercapacitor device consisting of this nanocomposite and activated carbon exhibits excellent cycling stability (90.2% of initial capacity after 3000 cycles), high energy density of 86.3 W h kg−1 (at 237.7 W kg−1) and high power density of 3.88 kW kg−1 (at 28.7 W h kg−1). This study ascribes the unprecedented performance to the high conductive holey graphene with abundant mesopores, the uniformly distributed TiNb 2 O 7 network nanostructure and the synergetic effect between them. Based on these findings, the presented nanocomposite has great potential in high performance lithium ion hybrid supercapacitors. Graphical abstract Image 1 Highlights • A novel composite of TiNb 2 O 7 network nanostructure and holey graphene was fabricated. • The long-term life with 91.5% capacity retention after 1000 cycles was obtained. • The Li-HSC device exhibits high energy density and excellent cycling stability. [ABSTRACT FROM AUTHOR]

Tin-based metal oxides usually suffer from severe capacity fading resulting from aggregation and considerable volume variation during the charge/discharge process in lithium ion batteries. In this work, a novel nanocomposite (MTO/N-RGO) of hollow amorphous MnSnO 3 (MTO) nanoparticles and nitrogen-doped reduced graphene oxide (N-RGO) has been designed and synthesized by a two-step method. Firstly, the nitrogen-doped graphene nanocomposite (MTO/N-RGO-P) with MnSn(OH) 6 crystal nanoparticles was synthesized by a facile solvothermal method. Subsequently, the MTO/N-RGO nanocomposite was obtained through the post heat treatment of MTO/N-RGO-P. The designed heterostructure and well-combination of the hollow amorphous MTO and N-RGO matrix can accelerate the ionic and electronic transport, and simultaneously accommodate the aggregation and volume variation of MTO nanoparticles during the lithiation–delithiation cycles. The as-prepared hybrid of MTO and N-RGO (MTO/N-RGO) exhibits a high reversible capacity of 707 mAh g −1 after 110 cycles at 200 mA g −1 , superior rate capability, and long-term cyclic life with high capacity of 610 mAh g −1 over 1000 cycles at 400 mA g −1 . Superior capacity retention of 97.3% over 1000 cycles was obtained. This work opens new opportunities to fabricate the high-performance electrode materials with heterostructure for lithium storage systems, especially for novel multi-metal oxide based nanocomposites with high cycling stability. [ABSTRACT FROM AUTHOR]

We report on the hydrothermal synthesis of boron-doped carbon dots (B-CDs) starting from glucose and boric acid. Doping of the CDs with boron was confirmed by Fourier transform infrared and X-ray photoelectron spectroscopy. The B-CDs have an average diameter of about 4 nm and display blue fluorescence which is dynamically quenched by Fe(III) ions. This finding was exploited to design a method for the determination of Fe(III) in water. The relative fluorescence intensity at 359 nm in the presence and of absence ions is inversely proportional to the concentration of Fe(III) ions, and a Stern-Volmer calibration plot is linear in the concentration range of 0-16 μM, with a 242 nM detection limit. The assay is sensitive, robust and selective. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

The physicochemical property of chemically prepared graphene can be significantly changed due to the incorporating of heteroatoms into graphene. In this article, boron-doped graphene sheets are used as carbon substrates instead of graphene for loading polyaniline by in situ polymerization. Compared with the individual component and polyaniline/non-doped graphene, the sandwich-like polyaniline/boron-doped graphene exhibits remarkably enhanced electrochemical specific capacitance in both acid and alkaline electrolytes. In a three-electrode configuration, the hybrid has a specific capacitance about 406 F g −1 in 1 M H 2 SO 4 and 318 F g −1 in 6 M KOH at 1 mV s −1 . In the two-electrode system of a symmetric supercapacitor, this hybrid achieves a specific capacitance about 241 and 189 F g −1 at 0.5 A g −1 with a specific energy density around 19.9 and 30.1 Wh kg −1 , in the acid and alkaline electrolytes, respectively. The as-obtained polyaniline/boron-doped graphene hybrid shows good rate performance. Notably, the obtained electrode materials exhibit long cycle stability in both acid and alkaline electrolytes (∼100% and 83% after 5000 cycles, respectively). The improved electrochemical performance of the hybrid is mainly attributed to the introduction of additional p -type carriers in carbon systems by boron-doping and the well combination of pseudocapacitive conducting polyaniline. [ABSTRACT FROM AUTHOR]

Abstract: Organic compounds as functional materials have attracted much keen interest in the past three decades owing to their potential applications in science and technology. Currently, great efforts have been made in looking for suitable photo-responsive materials among the multifarious organic compounds. Herein we reported the photophysical properties of 2-furanylmethylene-aminoantipyrine (FMAAP), benzylideneaminoantipyrine (BIAAP) and cinnamilideneamino-antipyrine (CIAAP) studied by a combined experimental and theoretical investigation. Two-photon absorption measurements give the cross-section values of 1.350×10−50 cm4 s/photon for FMAAP, 1.046×10−50 cm4 s/photon for BIAAP and 2.047×10−50 cm4 s/photon for CIAAP. The calculated first-hyperpolarization values are of 2.303×10−30, 1.257×10−29, 2.889×10−29 cm5/esu for FMAAP, BIAAP and CIAAP, respectively. UV–vis spectroscopy technique further reveals that the studied compounds display long-range electron transfer characteristics by absorbing light of specific wavelengths of 294.5nm for FMAAP, 293.2nm for BIAAP and 303.1nm for CIAAP. All the results indicate that the studied compounds are promising candidates of functionally photo-responsive materials. [Copyright &y& Elsevier]

Abstract: Mobile counter anion exchange of electropolymerized polyaniline (PANI) films with the anions in acid solutions has been investigated by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), scanning electron microscopy, Raman, UV–vis, and fluorescence spectra. The studied acids include camphorsulfonic acid, p-toluene sulfonic acid, HCl, HClO4, H2SO4 and H3PO4. In two cases of small and large counter ions of PANI films, CV tests have been performed alternately three times in each of two electrolytes containing organic or inorganic acid. The investigation of electrochemical and spectrophotometric measurements reveals that large counter anions can be easily replaced by the small anions; and the reverse exchange also occurs, but shows very low efficiency. This indicates that the achieved anion exchange in both cases leads to the remarkable alteration in electrochemical behavior and electrical conductance of PANI films. This implies counter anions, whatever the original or redoping ones, play an important role in the electrical, electrochemical, even optical properties of PANI. However, the polymer morphology does not be changed after exchange tests. This allows us to point out a ‘morphology-memory’ effect which is very significant for the development and application of PANI films with the same morphology and different properties. [Copyright &y& Elsevier]

Abstract: A novel high-performance electrode material based on fibrillar polyaniline (PANI) doped with graphene oxide sheets was synthesized via in situ polymerization of monomer in the presence of graphene oxide, with a high conductivity of 10Scm−1 at 22°C for the obtained nanocomposite with a mass ratio of aniline/graphite oxide, 100:1. Its high specific capacitance of 531F/g was obtained in the potential range from 0 to 0.45V at 200mA/g by charge–discharge analysis compared to 216F/g of individual PANI. The doping and the ratio of graphene oxide have a pronounced effect on the electrochemical capacitance performance of the nanocomposites. [Copyright &y& Elsevier]

Abstract: The interactions of promethazine hydrochloride (PZH) with thiolated single-stranded DNA (HS-ssDNA) and double-stranded DNA (HS-dsDNA) self-assembled on gold electrodes have been studied electrochemically. The binding of PZH with ssDNA shows a mechanism containing an electrostatic interaction, while the mode of PZH interaction with dsDNA contains both electrostatic and intercalative bindings. The redox system belongs to the category of diffusion control approved by cyclic voltammetry (CV). The diffusion coefficients of PZH at the bare, HS-dsDNA and HS-ssDNA modified gold electrodes decrease regularly as 1.34×10−3 cm2 s−1, 1.04×10−3 cm2 s−1, 7.47×10−4 cm2 s−1, respectively. The electron transfer standard rate constant k s of PZH at bare gold, HS-ssDNA and HS-dsDNA modified electrodes are 0.419s−1, 0.131s−1, and 0.154s−1, respectively. The presence of adsorbed dsDNA results in a great increase in the peak currents of PZH in comparison with those obtained at a bare or ssDNA adsorbed gold electrode. The difference between interactions of PZH with HS-ssDNA and HS-dsDNA has been used for hybridization recognition of 14-mer DNA oligonucleotide. The peak current (i pa) of PZH is linearly proportional to the logarithmic concentration of complementary target DNA in the range from 2.0×10−9 molL−1 to 5.0×10−7 molL−1 with the detection limit of 3.8×10−10 molL−1. [Copyright &y& Elsevier]

The influence of polymerization conditions on the morphology of thin films of poly-(N-methylaniline) (PNMA) was studied. The films were prepared by electropolymerization on gold and platinum electrodes and studied by optical and electron microscopy. It was demonstrated that the film morphology does not depend on the polymerization rate or on the electrode metal. However, it is sensitive to the kind of counter ion of PNMA. The polymers containing acetate or chloride do not form stable films. Polymer films containing phosphate or sulfate display inhomogeneous structures. A formation of sprouts and “nanotubes” was observed for PNMA sulfate. The films formed by PNMA perchlorate are smooth and transparent (glass-like structure). A sublayer of 4-aminothiophenol increases the adhesion of polymers to the gold surface. [ABSTRACT FROM AUTHOR]

A conventional resistance measured by two-point technique includes bulk and contact components. The contact resistance can be excluded by a four-point technique. A simultaneous use of the two- and four-point techniques allows to separate the total resistance between two electrodes for the contact and bulk parts. This approach has been used to analyze electrical coupling between metal electrodes of interdigitated structures and chemically sensitive coating formed by polyaniline (PANI). The polymer layers were deposited by electropolymerization on bare gold and platinum electrodes as well as on gold electrodes precoated by a self-assembled monolayer of 4-aminothiophenol. An exposure of the PANI films formed on interdigitated structures to gaseous HCl displays proportional changes of resistance measured by the two- and four- point techniques for platinum electrodes and for the precoated gold electrode, while a strong deviation from this proportionality was observed for the gold electrodes without precoating. The results demonstrate a high contribution of the contact resistance between PANI and bare gold electrodes into the resistance measured by the two-point technique. This contribution is small and therefore not measurable for bare platinum electrodes or for gold electrodes coated by 4-aminothiophenol. [Copyright &y& Elsevier]

CoP nanoparticles confined in PBA-derived nanocubes supported on MXene for efficient electrocatalytic water splitting. [Display omitted] • Simply synthesis method: Simple coprecipitation-phosphatization two steps to synthesis the heterojunction between CoP and Ti 3 C 2 T x MXene (CoP/Ti 3 C 2 T x). • Outstanding electrochemical performance: The catalyst CoP/Ti 3 C 2 T x exhibits impressive overpotentials of 103 mV and 312 mV for HER and OER, respectively, to afford 10 mA cm−2 in 1.0 M KOH and maintain for 24 h. • Thorough theoretical calculation verification: The DFT calculations reveal that the introduction of Ti 3 C 2 T x MXene can significantly enhance the electrochemical performance towards water splitting. The exploration of bifunctional catalyst with economic, durable, and efficient performance plays a crucial role to boost both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in overall water splitting. Herein, we report a feasible strategy to design effective heterostructure between CoP and Ti 3 C 2 T x MXene (denoted as CoP/Ti 3 C 2 T x). This approach allows for the growth of CoP nanoparticles with uniform size of 5 nm on the Ti 3 C 2 T x MXene, further enhancing the water electrolysis efficiency. The CoP/Ti 3 C 2 T x bifunctional catalyst demonstrates an exceptional HER activity with a satisfactory overpotential of 103 mV at 10 mA cm−2, and also can drive 10 mA cm−2 for OER with the overpotential of 312 mV in 1.0 M KOH. Moreover, the CoP/Ti 3 C 2 T x -based electrolyzer exhibits high electrochemical stability for 24 h with a low required voltage of 1.66 V at 10 mA cm−2. The density functional theory (DFT) calculations reveal that the introduction of Ti 3 C 2 T x MXene significantly adjusts d-band center towards Fermi level and expand total density of states, resulting in great electrical conductivity, enhanced water adsorption, and activation. This study provides an available mode for effective design and construction of non-noble-metal-based dual-functional catalyst toward practical energy conversion. [ABSTRACT FROM AUTHOR]

Abstract: Poly (o-phenylenediamine) (PoPD) hollow multi-angular microrods have been synthesized at 10 °C via an interfacial process using ferric chloride and o-phenylenediamine (oPD) as starting materials. The chemical structure of the one dimensional (1D) superstructure is proved to be phenazine-like, and contains the benzenoid and quinoid imine units doped partly with Cl. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) observations indicate that the resulting superstructure of PoPD is built from hollow nanofibers aligned parallel to the fiber axis by van der Waals'' force. The possible formation mechanism of the structure has been proposed. [Copyright &y& Elsevier]

The functionalized graphene/montmorillonite (FG/MTT) nanosheet was synthesized through chemical bonding by a simple, green method, which had remarkable dispersion stability in oil and its lubricating performance was evaluated by a four-ball tribometer. The test results showed that FG/MTT had a preeminent lubricant property when the concentration was 0.4 mg/ml. Compared with the bare oil sample, its average friction coefficient (FC) and wear scar diameter (WSD) decreased by 50.4% and 13.2%, respectively. The synergistic effect between FG and MTT was further explored by comparing the lubricant mechanism of the different additives. After synthetically analyzing worn surface by means of scanning electron microscopy and X-ray photoelectron spectroscopy, the lubrication mechanism of the FG/MTT nanocomposite as oil additive was discussed and postulated: the FG/MTT with weak interlayer adhesion was filled between the friction pairs to avoid contact and clinging of some asperities, and the sliding between the layers played a role in lubrication. Furthermore, FG/MTT would react with the surface of the friction pair to form a repair layer composed of Fe2O3, SiC, SiO2, and aluminosilicate, mending the grinding surface and promoting the hardness after friction. [ABSTRACT FROM AUTHOR]

Heterostructured composites, inheriting the integrated properties of the individual components due to the synergistic effect, have engendered great attention in materials science and energy storage. However, conventional biphasic heterostructures not only optimize the performance of the composites but also aggregate the inevitable drawbacks, which can be addressed with the construction of the triphasic heterostructures by introducing an appropriate intermediate phase, significantly. Herein, a two‐dimensional (2D) double‐heterostructures MoSe2‐TiO2‐MXene anode is architected for Li‐ion storage, which combines the advantages of the high theoretical capacity of MoSe2 and metallic conductivity of MXene. Besides, the in‐situ derived TiO2 can alleviate the irreversible phase transition of MoSe2, arising from the low electronic/ionic conductivities, through electronic coupling effects. Meanwhile, the intermediate phase of TiO2 can further prevent the restacking issue of MXene, thus sustaining its high conductivity. Finally, the three‐dimensional (3D) printing technology is employed to further improve the kinetics of the electrodes for Li‐ion capacitors (LICs), which deliver the power density of 5563 W kg−1 at an energy density of 51 Wh kg−1, and a remarkable cycling stability for 20 000 cycles at 1 A g−1. This work deepens the understanding of the influence of heterostructured engineering on the design of high‐energy/power storage devices. [ABSTRACT FROM AUTHOR]

A sandwich "signal-off" type photoelectrochemical (PEC) immunosensor was fabricated based on a composite heterojunction of tungsten oxide/titanium oxide microspheres (WO3/TiO2) acting as signal amplification platform and carbon microspheres loaded by gold nanoparticles (Cs@Au NPs) utilized as the label for detecting antibody. WO3/TiO2 had excellent photoelectric performance, and the results of Mott-Schottky plots, open-circuit voltage, and electron spin resonance spectroscopy indicated that it belonged to the Z-scheme heterojunction transfer mechanism of photogenerated carriers. To achieve the sensitization of PEC immunosensor, Cs@Au NP–labeled immunocomplex can effectively reduce the photocurrent signal. The PEC immunosensors were fabricated under the optimal conditions of 1:1 WO3/TiO2 (molar ratio), 2.0 mg mL−1 WO3/TiO2, and 1.5 mg mL−1 Cs@Au NPs. Through comparison of the detection results of label-free and sandwich-type PEC immunosensors for nucleocapsid (N) protein of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), we found that the sensitivity of the sandwich type was 2.53 times the label-free type, and the limit of detection was 0.006 ng mL−1, i.e., 3.17 times lower than the label-free type. This demonstrates that the developed sandwich-type PEC immunosensor will have a brighter application prospect. [ABSTRACT FROM AUTHOR]

Based on signal amplification strategy of dendritic mesoporous silica nanospheres loaded with CdSe/ZnS quantum dots (DMSN@QDs), an ultrasensitive electrochemiluminescence (ECL) immunosensor with magnetic separation was constructed for the detection of SARS-CoV-2 nucleocapsid protein (NP). DMSN, a mesoporous material with abundant radial pores, large specific surface area and high porosity, can increase the loading capacity of QDs and hinder their aggregation as the nanocarrier. DMSN@QDs with good ECL efficiency were used as signal labels to construct a sandwich immunosensor. The designed ECL immunosensor displayed a good linear relationship for NP concentrations ranging from 0.005 ng mL−1 to 50 ng mL−1, with a limit of detection of 3.33 pg mL−1. The ECL immunosensor was successfully applied to detect NP in human serum samples with satisfactory recovery. This strategy provided a new method for detecting NP and expanded the application field of DMSN. [ABSTRACT FROM AUTHOR]

A stable and well-distributed nitrogen-doped graphene (NGE) is prepared by a simple and efficient hydrothermal method with a reducing-doping reagent of vitamin B3. Compared with NGE reduced by urea, vitamin B3 reduced NGE (NGE-N) show superior catalysis towards the electrochemical reduction of imidacloprid. The pyridine-N oxide induced in graphene sheets is considered enhancing the interaction between NGE-N and imidacloprid molecules. The NGE-N modified electrode is used in fast determination of imidacloprid with a low detection limit of 0.55 μM. [ABSTRACT FROM AUTHOR]

A virus-like hybrid material constituted by CoP nanoparticles confined in porous N-doped carbon framework decorated with N-doped carbon nanotubes for efficient water splitting. [Display omitted] Exploration of catalysts for water splitting is critical for advancing the development of energy conversion field, but designing bifunctional catalysts remains a major challenge. Herein, we demonstrate the N-doped carbon nanotube (NCNT)-grafted N-doped carbon (NC) framework embedding CoP nanoparticles (CoP@NC/NCNT) as hydrogen and oxygen evolution reaction (HER and OER) catalysts for water splitting. As a result, the CoP@NC/NCNT electrode requires the overpotentials of 106 and 177 mV at 10 mA cm−2 in 0.5 M H 2 SO 4 and 1.0 M KOH solutions for HER, respectively. Moreover, an overpotential of 324 mV for OER can drive 10 mA cm−2 in 1.0 KOH. The CoP@NC/NCNT-based electrolyzer derives a current density of 10 mA cm−2 at a low voltage of 1.72 V in 1.0 M KOH and remains stable for 10 h. The outstanding electrocatalytic performance is mainly attributed to the hierarchical structure with rich branches and highly active component of CoP. The intimate contacts between hierarchical porous NC frameworks by cross-linked NCNTs create a 3D conductive network, which facilitates electron or mass transfer and activates CoP. This work offers a novel route for preparing hierarchical carbon framework encapsulated metal phosphide particles for potential applications in energy conversion field. [ABSTRACT FROM AUTHOR]

A sensitive dual-readout immunosensor for fluorescence and electrochemiluminescence (ECL) detection of ricin was established, which was combined with a streptavidin–biotin signal amplification system. CdSe/ZnS quantum dots with fine fluorescence and ECL properties were used as the dual-signal function probes of the sandwich immunocomplex. Under the optimum experimental conditions, the dual signal intensity increased significantly with the rise in ricin concentration. The fluorescence intensity of the senor exhibited a good liner relationship toward the ricin concentrations with 0.1~100 ng/mL and the limit of detection (LOD) was 81.7 pg/mL; taking ECL as the detection signal, the sensor showed a linear relationship with the ricin concentrations ranging from 0.01 ng/mL to 100 ng/mL and the LOD was 5.5 pg/mL. The constructed sensor with high sensitivity had been successfully applied to the detection of ricin in complex matrices with satisfactory recoveries. The proposed immunosensor model can be extended to the analysis and detection of others target proteins. [ABSTRACT FROM AUTHOR]

The synthesis of multi‐carbon products through electrochemical CO2 reduction reactions has attracted great interest from researchers. Herein, nitrogen‐ and carbon‐doped copper nanocatalyst (NC−Cu) containing abundant Cu−N−C active sites was prepared by thermal decomposition of the complexes containing copper and melamine. The NC−Cu catalyst exhibited an ideal current density of 22 mA cm−2 at −0.93 V versus reversible hydrogen electrode (vs. RHE) in CO2‐saturated 0.5 M KHCO3 medium, with ethanol as the predominant product at −0.93 V (vs. RHE) and a maximum Faraday efficiency of 31 %. The current density of the catalyst remained almost unchanged after 20 h of electrolysis, indicating its excellent stability. The excellent catalytic ability is attributed to the abundant Cu−N−C active sites of NC−Cu with 3D porous microstructure. [ABSTRACT FROM AUTHOR]

A simple and sensitive label-free electrochemical biosensor for nimodipine was fabricated by using nitrogen-doped graphene (NGE) modified electrode. The surface morphology and electron transfer behavior of the modified electrodes were studied by scanning electron microscopy and electrochemical impedance spectroscopy, respectively. The electrochemical behaviors of nimodipine at the modified electrodes were investigated by using cyclic voltammetry. On the basis of the excellent electrocatalytic activity of NGE, an obvious cathodic peak of nimodipine could be caused at the NGE modified glassy carbon electrode (GCE), moreover, the electrochemical signal was greatly enhanced compared with the undoped graphene modified GCE. Under the optimized conditions, the present sensor showed excellent performances for nimodipine detection including wide linear range of 0.02–3 μM, low detection limit (9.1 nM), good selectivity to the general coexisted interferences, etc. The proposed biosensor was also successfully applied to validate its capability for the analysis of nimodipine in tablets. The work would promote the potential application of NGE as an excellent material in fabricating electrochemical sensors for chemical or biochemical analysis. [ABSTRACT FROM AUTHOR]

[Display omitted] Effective removal of antibiotics in the environment can be a demanding issue concerning the ecosystem and human health. Photocatalysis and peroxymonosulfate (PMS) oxidation have become important methods to effectively remove stubborn pollutants. In this work, by integrating these two technologies, an efficient system for degrading chloramphenicol (CAP) in water was proposed. The system was constructed by coupling strontium-doped lanthanum cobaltate (LSCO5) with chlorine-doped carbon nitride (CGCN). By doping, the increase of oxygen vacancy and the adjustment of bandgap were realized. Photoluminescence and electrochemical impedance experiments showed that the heterojunction can promote electron transfer and photogenerated carrier separation. Under the synergistic effect of PMS oxidation and photocatalysis, the prepared composite with an optimal loading of 40% LSCO5 can degrade 95.6% of CAP within 20 min. Degradation experiments on different pollutants proved the versatility of the catalytic system. The enhanced degradation mechanism of CAP was explored based on the assessment of the degradation efficiency of CAP, electron paramagnetic resonance (EPR), and quenching experiments. Through liquid chromatography-mass spectrometry (LC-MS) analysis, a possible route for CAP degradation was also proposed. This research provides some inspiration for the remediation of polluted water with perovskite-based catalyst under the synergistic effect of PMS and photocatalysis. [ABSTRACT FROM AUTHOR]

Long-cycle stability and high-energy density are big challenges for developing high-performance hybrid supercapacitor (HSC) electrode materials. In this work, molybdenum-doped Co3O4 nanosheets arrays on nickel foam (noted as MoxCo1.5−xO/NF) are successfully prepared via facile one-step electrodeposition followed by annealing for hybrid supercapacitors. The experimental and calculated results indicate that the band gap modification and conductivity enhancement of MoxCo1.5−xO lead to excellent capacitive performance due to the doping of Mo into Co3O4. The as-prepared Mo0.25Co1.25/NF electrode demonstrates a high specific capacity of 128.2 mAh g−1 (923 F g−1) at 1 A g−1 (60% higher than the undoped Co3O4) and superior cycle stability with 95.2% capacity retention after 10,000 cycles at 10 A g−1. The assembled HSC delivers high-energy density of 64.3 Wh kg−1 at the power density of 794.1 W kg−1 and with 87.7% capacity retention after 10,000 cycles. This work can present a new strategy to fabricate the three-dimensional high-performance integrated electrode materials by a facile electrodeposition for heteroatom-doped transition metal oxide for high-performance supercapacitors. [ABSTRACT FROM AUTHOR]

Abstract: To improve the electrochemical properties of chemically synthesized graphene hybrids, nitrogen-doped (N-doped) graphene decorated with M(OH) x (M=FeO, Ni, Co) nanoparticles were fabricated by a one-pot method at a mild temperature (95°C). Urea plays an important role in the synthesis process; it not only acts as the reducing agent and doping agent for N-doped graphene, but also as a hydroxyl donor for the fabrication of metal hydroxides and oxide-hydroxide. With the help of N-doped graphene and urea, FeOOH nanorods, Co(OH)2 nanowires and flower-like Ni(OH)2 nanoparticles were grown on the graphene sheets. The N-doped graphene hybrids exhibited the significantly improved electrochemical performances compared to the undoped equivalents or the separate components. [Copyright &y& Elsevier]

Modulation of oxygen vacancy concentration of Nb 2 O 5 anode, arising from quantitative regulation of oxygen content in the precursor, is developed, revealing the relationship between the oxygen vacancy concentration and kinetics for Li-ion storage. In addition, the integrated binder-free electrode with appropriate oxygen vacancies and highly conductive N-doped carbon porous framework results in improved kinetics for the anode of Li-ion capacitors. [Display omitted] • Oxygen vacancy concentration of Nb 2 O 5 @NC anode is quantitative regulation. • Revealing relationship between oxygen vacancy concentration and kinetics of Li-ion storage. • Nb 2 O 5 @NC binder-free electrode is constructed via electrophoretic deposition. • Binder-free electrode further improves kinetics for the anode of Li-ion capacitors. Introducing appropriate oxygen vacancies (OVs) improves the integral conductivity of the Nb 2 O 5 anode of Li-ion capacitors (LICs). Whereas a few recent studies link the OVs level and the kinetics of Nb 2 O 5 , the quantitative relationship between the OVs and the performance of Nb 2 O 5 remains elusive. Herein, we show that the OVs concentration in Nb 2 O 5 can be quantitatively manipulated by regulating the oxygen content in niobium complex (NbL) precursors, thus controlling the kinetics of the Nb 2 O 5 -based anode. The OVs concentration is inversely proportional to the oxygen content in the NbL, where it facilitates the electronic transfer and the Li-ion migration of Nb 2 O 5 with optimal introduction. In addition, the ligand in the NbL can also be used as a sacrificial template for creating an N-doped carbon coating wrapping Nb 2 O 5 nanoparticles with OVs to further improve the electronic conductivity of the composite. This was followed by depositing the NbL nanoparticles via electrophoretic deposition for assembling binder-free electrodes. The integrated electrode-based LICs deliver 76 μWh cm−2 at 550 μW cm−2 and retain 94 % of the capacity after 5000 cycles. This work provides a new recognition for the design of metal oxide electrodes with fast kinetics for LICs from material modification to electrode material assembly. [ABSTRACT FROM AUTHOR]

Highlights: [•] CoMoO4/Graphene composites were prepared via one-step hydrothermal method. [•] The composites have high surface/body ratios and large electroactive regions. [•] The composites present better electrochemical properties than pure-CoMoO4. [•] The composite achieves a capacitance of 394.5Fg−1 at 1mVs−1. [ABSTRACT FROM AUTHOR]

Abstract: A novel conducting poly (N-phenyl-2-naphthylamine) (PPBNA) film was successfully electropolymerized by direct anodic oxidation of its monomer N-phenyl-2-naphthylamine in boron trifluoride diethyl etherate. The prepared PPBNA films showed good redox activity and structural stability even in concentrated sulfuric acid. The impedance spectra of PPBNA films demonstrated that the electron transfer resistance was around 80Ω. The fluorescent results indicated that the emission band of PPBNA was red-shifted about 30nm in comparison with that of the monomer. The fluorescent spectra exhibited that the monomer and PPBNA films were excellent blue-light-emitting and blue-green-light-emitting material, respectively. [ABSTRACT FROM AUTHOR]

Abstract: The optical properties of electrochemically polymerized N-methylaniline are changed in the presence of gaseous hydrogen chloride. This effect was used for preparation of chemical sensors with transduction based on surface plasmon resonance. The interaction of hydrogen chloride with a two nm layer of poly-(N-methylaniline) on gold leads to the shift of the surface plasmon resonance. The analysis of the resonance spectra demonstrates that the effect is caused by an increase of the imaginary component of the refractive index; a minor contribution is also provided by film condensation leading to an increase of the real component of the refractive index and a decrease in the thickness. The effect is selective and quasi-reversible. The concentration dependence of the gas effect obeys Langmuir''s adsorption isotherm with a reciprocal value of the binding constant of 850 ± 160ppm. [Copyright &y& Elsevier]

Controlling the morphology of metal–organic frameworks to improve their application in energy storage remains a particular challenge. In this work, hollow porous Co-MOF-74 nanocuboids consisting of nanothorn (< 7 nm) are designed through the linker exchange method for the improved MOFs-based anode of the lithium-ion battery. The Co-MOF-74 inherits the shape of cobalt acetate hydroxide prism and translates into the hollow structure due to the Kirkendall effect. The evolutions of morphology depending on temperature have been investigated further together with the lithium storage performances. Due to the combined merits from the high surface area inheriting from the nanocuboids and the coordination defects originating from the ultrasmall nanothorns, the Co-MOF-74 with optimized morphology exhibits a high reversible capacity and excellent cycle stability (up to 900 mAh g−1 at 1000 mA g−1 after 600 cycles). This work demonstrates an effective way for rational design and synthesis of MOFs-based electrodes for energy storage. [ABSTRACT FROM AUTHOR]

Lithium–sulfur (Li–S) batteries are widely regarded as the most promising batteries for the future due to their higher specific capacity and lower prices. Various strategies are utilized to alleviate the shortcomings of Li–S batteries failing to reach theoretical capacity. However, basic research at the molecular level continues to be lacking. Therefore, we use molecular dynamics to study the details of the solvated structure of Li–S batteries electrolyte and the nature of the transport process, revealing the relationship between the solvated structure of the electrolyte of LiPF6 and the organic solvent ethylene carbonate/dimethyl carbonate (EC/DMC). The electrolyte of Li2S4 was first simulated in a pure solvent environment. Then the LiPF6 salt was added to the model to simulate a typical electrolyte for a working Li–S battery. Regarding the rationality of the solvent system, various reference systems such as density, dielectric constant, viscosity and diffusion coefficient of the solvent were used for verification. And the detailed composition of the first solvation shell of the polysulfate ion and the coordination number of the ions are discussed. These results provide new insights into the use of EC/DMC electrolytes in Li–S batteries, while at the same time providing a basis for efficient future predictions of electrolyte structure and transport in complex electrode confinements. The radius of the first solvation shell of each component is the PF 6 − anion at about 0.22–0.28 nm, the DMC solvent at about 0.32–0.36 nm and the EC solvent at about 0.41 nm, respectively. The first solvation shell according to these distributions has a radius of about 0.5 nm. The coordination number in the first solvation shell is plotted, which is about 1.88 for PF 6 − , 1.86 for DMC, and about 0.14 for EC. In conclusion, 3.88 molecules are produced in the first solvation shell of the ion. [ABSTRACT FROM AUTHOR]

The utility of TiO 2 as an anode for lithium-ion storage is hindered by low conductivity and sluggish ionic diffusion. Here, the 2D N-doped carbon-wrapped TiO 2 (TiO 2 @NC) composite with a thickness of 5.5 nm derived from the 2D metal-organic framework was designed. This composite consisting of TiO 2 nanoparticles embedded in ultrathin N-doping carbon was used to address the rate and cyclability of Li-ion batteries. The 2D nanosheet morphology obtained from Ti 8 O 8 (OH) 4 (BDC-NH 2) 6 （NH 2 -MIL-125 (Ti)）effectively increases the specific surface area and shortens the electron/ion transport pathway. The chemical bond of Ti-C-O between TiO 2 nanocrystals and N-doping carbon further improve conductivity. Due to its unique structure, the produced TiO 2 @NC composite shows excellent cyclability with a reversible capacity of 110 mAh g–1 after 2000 cycles at 0.5 A g–1. Furthermore, the 2D TiO 2 @NC exhibits outstanding rate performance (71 mAh g–1 at 5 A g–1) compared to bulk TiO 2 @NC. This general concept can be extended to the development of metal oxide materials based on insertion mechanisms, such as Nb 2 O 5. • The 2D TiO 2 @N-doping carbon composite with a thickness of 5.5 nm is prepared. • Solvent-dependent variation of morphology NH 2 -MIL-125(Ti) MOF is investigated. • The TiO 2 nanocrystals embedded in ultrathin N-doping carbon nanosheets via chemical bonding. • The TiO 2 @N-doping carbon composite shows excellent lithium-ion storage performances. [ABSTRACT FROM AUTHOR]

The repeated outbreaks of coronavirus disease 2019 (COVID-19) have seriously threatened human health and economic development. Therefore, it is still significant to explore an efficient method for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) detection. Herein, we designed a dual-mode colorimetric and fluorescent immunosensor based on Fe2+ doped ZIF-67 derivatives-based composites, Pt nanoparticles loaded on CoFe nanoparticles embedded porous carbon-nitrogen hexahedron (CoFe/NC@Pt), for detecting SARS-CoV-2 nucleocapsid protein. The doping of Fe2+ generated bimetallic CoFe nanoparticles and formed more defects after pyrolysis. Meanwhile, the peroxides-like activity significantly improved owning to the synergistic effect of Co and Fe nanoparticles. Furthermore, loaded Pt nanoparticles not only provided more active sites, but also could couple antibodies by modifying functional groups. CoFe/NC@Pt exhibited good peroxidase-like activity and could catalyze the oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB) to blue oxides in the presence of H 2 O 2 , generating visible color signals. While the oxTMB could quench the fluorescence of carbon dots through inner filter effect, thereby providing fluorescent signals. The limit of detection were 0.022 ng/mL (colorimetric) and 0.018 ng/mL (fluorescent). And the specificity of the immunosensor was verified by comparing with other interferents. Therefore, this dual-mode immunosensor with good performance provided a reliable strategy for diagnosis of COVID-19. [Display omitted] • A dual-mode colorimetric and fluorescent immunosensor based on CoFe/NC@Pt nanozyme. • CoFe/NC@Pt exhibited good peroxidase-like activity. • The quenching mechanism of CDs was inner filter effect. • The accuracy of the sensor was improved by mutual authentication of double signals. [ABSTRACT FROM AUTHOR]

[Display omitted] • Au@CeO 2 @Pt nanoenzymes exhibited an outstanding peroxidase-like activity. • A colorimetric-fluorescent dual-mode assay for SARS-CoV-2 was constructed. • The immunosensor achieved detection in simulated samples with satisfactory results. Developing powerful alternatives to natural enzymes has been a target pursued by researchers, and nanozymes are considered to be the best candidate due to their unique advantages of high stability, high activity, and easy modification. In this study, the multishell complexes of Au@CeO 2 @Pt nanozymes were successfully synthesized which exhibited an excellent intrinsic peroxidase-like ability to oxidize 3,3′,5,5′-tetramethylbenzidine (TMB), and resulting in a visible colorimetric signal. Interestingly, due to the internal filtration effect, the blue-emitting oxidized TMB (oxTMB) can also quench the red-emitting light from bimetallic AuAg nanoclusters. Based on the above properties, a kind of robust immunoassay for target protein detection was established. The dual-mode immunoassay is more accurate for SARS-CoV-2 detection on account of the reciprocal corroboration of the signals. More importantly, the immunoassay had high sensitivity with a low limit of detection and excellent recovery rates in simulated urine/saliva samples. Therefore, it is highly anticipated the immunoassay based on the newly developed nanozyme became an accurate instrument for diagnosing SARS-CoV-2 in the biomedical field. [ABSTRACT FROM AUTHOR]

Wearable electronic devices are the new darling of consumer electronics, and energy storage devices are an important part of them. Here, a wearable lithium‐sulfur (Li‐S) bracelet battery using three‐dimensional (3D) printing technology (additive manufacturing) is designed and manufactured for the first time. The bracelet battery can be easily worn to power the wearable device. The "additive" manufacturing characteristic of 3D printing provides excellent controllability of the electrode thickness with much simplified process in a cost‐effective manner. Due to the conductive 3D skeleton providing interpenetrating transmission paths and channels for electrons and ions, the 3D Li‐S battery can provide 505.4 mAh g−1 specific capacity after 500 cycles with an active material loading as high as 10.2 mg cm−1. The practicality is illustrated by wearing the bracelet battery on the wrist and illuminating the red light‐emitting diode. Therefore, the bracelet battery manufactured by 3D printing technology can address the needs of the wearable power supply. [ABSTRACT FROM AUTHOR]

Oxygen reduction reaction (ORR) plays a key role in the application of fuel cells. Here, we used shaddock peel to fabricate a set of N, P dual-doped hierarchical porous carbons, abbreviated as NPSPs, where the carbons were carbonized, activated and dual-doped via a simple one-step pyrolyzation. Contrast results indicate the contents of pyridinic-N, graphitic-N and P–C species increase with the rising of temperatures, and the temperature also affects the degree of graphitization, surface area, morphology, thus influences the ORR performance. More importantly, the NPSP-900 demonstrates an outstanding ORR activity with a comparable half-wave potential (0.83 V vs. RHE) and higher current density with respect to commercial Pt/C, following 4e transfer pathway. Our work illustrates that NPSP-900 is a promising cathode for fuel cells because of its simple preparation, waste utilization, excellent ORR performance, good methanol tolerance and superior stability. Image 1 • One-step pyrolysis can accomplish carbonization, activation and N,P-dual doping. • NPSPs own hierarchical porous structures with high BET surface areas. • Higher temperature can enhance ORR activities with improved doping N/P species. • NPSP-900 owns a close ORR activity compared with Pt/C, following 4e transfer way. • NPSP-900 shows a remarkable methanol tolerance and superior stability. [ABSTRACT FROM AUTHOR]

An electrochemical sensor based on a glassy carbon electrode (GCE) modified by three-dimensional graphene (3D-GE) and polyglutamic acid (PGA) was developed to quantitatively detect Amoxicillin (AMX), a worldwide used antibiotic. AMX response at PGA/3D-GE/GCE involving the transfer of one electron and an equal number of protons were determined using electrochemical approaches. Density functional theory simulations were performed to give insights on the reaction mechanism of AMX on the surface of the modified electrode. When the optimization of the experimental conditions was completed, the linear range of AMX was 2–60 μM. Besides, the detection limit was calculated as 0.118 μM (S/N = 3). And the modified electrode could detect the concentration of the AMX in human urine samples. Overall, the developed PGA/3D-GE/GCE for determination of AMX shows great potentials in practice. Image 1 • A friendly and sensitive method for the determination of amoxicillin was developed. • Polyglutamic acid/three-dimensional porous graphene (PGA/3D-GE) was used for the modification of electrode. • A new reaction mechanism of amoxicillin was proposed by combining computational simulation with electrochemical methods. [ABSTRACT FROM AUTHOR]

• The discarded and cheap mulberry leaves was used to prepare bacterial cellulose. • The as-prepared composite shows good antimicrobial properties and biocompatibility. • The composite may be potential application in wound dressings. It's long been understood that antimicrobial properties are one of the most important function in the field of biomedicine. In this thesis, we introduce a new technique to functionalize bacterial cellulose (BC) with antimicrobial properties by in situ method. We design a series of experiments on hydrolyzing mulberry leaves and exploring the methods of fermenting and purifying to obtain a BC complex with antimicrobial properties. Meanwhile, the anti-bacterial performances of MH-BC (fermented by the mulberry leaves acid hydrolysate fermentation medium) were evaluated with Escherichia coli and Staphylococcus aureus , and the experimental results showed that the MH-BC have excellent anti-bacterial activities. Considering the excellent biocompatibility of MH-BC towards hMSCs, we expect that this antibacterial functional BC composite will find potential applications in biomedicine and regenerative medicine. [ABSTRACT FROM AUTHOR]

A dual-doping strategy was applied to fabricate the novel electrode materials. For the first time, the spinel hybrids of nanosized Ni x Co 1−x Fe 2 O 4 with N-doped graphene (N x -NG) were synthesized by a hydrothermal co-precipitation method. The size of Ni x Co 1−x Fe 2 O 4 (N x) nanoparticles on N-doped graphene can be tuned with the regulation of Ni/Co content. Among these nanocomposites, the Ni 0.4 Co 0.6 Fe 2 O 4 nanoparticles with the smallest average size of 10 nm are uniformly anchored on the N-doped graphene. The electrochemical characterizations display that the N 0.4 -NG exhibits the best electrochemical lithium storage performance compared to other five nanocomposites. It delivers a high capacity of 1367.0 mA h g−1 at the first discharge process，and the reversible capacity retention of 87% (2nd to 50th) at 0.1 A g−1. The excellent electrochemical performance of N 0.4 -NG can be owing to the small size of nanoparticles and its well-combination with N-doped graphene, which provide the large surface area and promote the ion/electron transfer rate. The synergistic effect resulted from the strong interaction between N 0.4 and N-doped graphene is contributed to the enhanced electrochemical performance of N 0.4 -NG. This study not only extends graphene-based electrode materials for lithium ion battery, but also promotes the development of energy resources. Unlabelled Image • A spinel hybrid of nanosized Ni x Co 1-x Fe 2 O 4 with N-doped graphene was fabricated. • Size of Ni x Co 1−x Fe 2 O 4 nanoparticles was tuned with the regulation of Ni/Co content. • A reversible capacity of 785.2 mA h g−1 of N 0.4 -NG after 50 cycles was obtained. [ABSTRACT FROM AUTHOR]

Abstract A novel fluorescent sensor based on g-C 3 N 4 nanofibers for the sensitive detection of dopamine (DA) has been proposed. We synthesized g-C 3 N 4 nanofibers by directly hydrolyzing bulk g-C 3 N 4 in the alkaline atmosphere (3 M NaOH). The obtained ultrathin g-C 3 N 4 nanofibers were verified by characterizations of Transmission electronic microscope (TEM), X-ray diffractometer (XRD), Fourier transformation-infrared (FT-IR) and X-ray photoelectron spectroscopy (XPS). It was found that the fluorescence intensity of g-C 3 N 4 nanofibers was obviously quenched by DA. Fluorescence resonance energy transfer (FRET) between DA and g-C 3 N 4 nanofibers led to the fluorescence reduction of g-C 3 N 4 nanofibers. The fluorescent probe based on g-C 3 N 4 nanofibers exhibits linear responses to the concentration of DA in the range from 0 to 4 μM and 4 to 20 μM, the limit of detection is 17 nM. The fluorescent probe shows excellent stability, good selectivity with its application in serums. Graphical Abstract Unlabelled Image Highlights • A rapid and sensitive approach for detection of DA has been reported. • The developed probe exhibits excellent stability and good selectivity. • The proposed g-C 3 N 4 nanofibers probe has been presented for DA detection in human serums. [ABSTRACT FROM AUTHOR]

Abstract A rapid and sensitive, non-enzymatic electrochemical detection of hydrogen peroxide (H 2 O 2) is of utmost importance for diagnosis and treatment of related diseases in clinical purpose. To meet this requirement, we report a simple and robust microwave-assisted synthetical route via prepared Gd 2 O 3 nanoparticles decorated reduced graphene oxide nanocomposite (Gd 2 O 3 NPs@RGO) modified electrode for non-enzymatic H 2 O 2 detection. The composition and morphological formation were characterized by using XRD, FT-IR, XPS, FESEM, and HRTEM. The impedance and cyclic voltammetry exhibit tremendous electrocatalytic capability and superior performance toward H 2 O 2 reduction. A sensitive and reproducible amperometric H 2 O 2 sensor was fabricated which was able to detect concentration as low as 1.57 nM. The method worked well even in clinical and biological samples, which indicates the reliability of the method in real time analysis. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Mn doped Co 3 O 4 (Mn x Co y O) deposited on NF presents mesoporous nanoneedle structure. • Mn 1.5 Co 0.75 O/NF shows remarkable capacitance retention of 104% after 10,000 cycles. • The assembled ASC shows high energy density of 10.63 Wh kg−1 (at 14.7 kW kg−1). Abstract Long–term cycling stability is an important criterion and big challenge for pseudocapacitive materials. Ultra-stable manganese doped Co 3 O 4 mesoporous nanoneedles were synthesized via one-step hydrothermal reaction followed by annealing grown on nickel foam (noted as Mn x Co y O/NF, x + y = 2.25) for supercapacitors. The Mn doping in Co 3 O 4 was confirmed by several techniques. Among various Mn x Co y O/NF electrodes, the Mn 1.5 Co 0.75 O/NF demonstrated the superior electrochemical performance, with an excellent cycling stability of 104% capacitance retention after 10 000 charge–discharge cycles at 6 A g−1, as well as a good capability (668.4 F g−1 at 1 A g−1 compared to that of undoped Co 3 O 4 which is 201.3 F g−1). Moreover, the assembled asymmetric supercapacitor based on Mn 1.5 Co 0.75 O/NF//graphene performs a high energy density of 25.88 Wh kg−1 (at 359.5 W kg−1) and a high power density of 14.7 kW kg−1(at 10.63 Wh kg−1). The improved electrochemical properties are mainly owing to the enhanced intrinsic conductivity and electrochemical activity of Co 3 O 4 after doped with appropriate Mn concentration. The three-dimensional nanostructure of mesoporous nanoneedle array grown on NF also provides short ion diffusion path and large active surface areas, contributing to the high rate performance and high energy density. This study may offer a new approach to fabricate the unique 3D nanostructured electrode materials based on doped metal oxides for supercapacitors with long-term cycling stability and high energy density. [ABSTRACT FROM AUTHOR]

Abstract Oxygen reduction reaction (ORR) and Lithium storage both play the key roles in energy conversion and storage devices. Here, we report a honeycomb-like nitrogen-doped carbon derived from enteromorpha algae (N-EA), using a one-step pyrolysis process at only 600 °C to simultaneously achieve doping, carbonization and activation. After anchoring CoFe 2 O 4 on N-EA, CoFe 2 O 4 /N-EA, not only inherits the high surface area, porous structure, active nitrogen species from N-EA, but also benefits from the active sites and high theoretical specific capacity of Li storage from CoFe 2 O 4. The synergistic effect makes CoFe 2 O 4 /N-EA an alternative catalyst to commercial Pt/C for ORR with superior activity and stability. Moreover, CoFe 2 O 4 /N-EA exhibits a remarkable cycle performance with a 100% capacity retention (∼900 mAh g−1) after 500 cycles at 0.5 A g−1. Green preparation, waste utilization, good ORR performance and Li storage property of CoFe 2 O 4 /N-EA could make it a promising candidate for fuel cells and LIBs. [ABSTRACT FROM AUTHOR]

Highlights • Graphene oxide (GO) hydrogel was induced by synergistic effect of pyrrole and Co2+. • S and N are doped in graphene framework with doping/reducing agent of L -Cysteine. • 3D-sturctrue are obtained via evaporation induced drying without freeze-drying. • The 3D S/N-co-doped graphene show enhanced response for hydroquinone and catechol. Abstract Herein, a three-dimensional self-assembled hydrogel of graphene oxide sheets induced by pyrrole and Co2+ is described. Controlled shrinkage and sulfur/nitrogen co-doping occurred in the subsequent hydrothermal process. The obtained 3D sulfur/nitrogen co-doped graphene was further dried through direct evaporation, without freeze-drying. SEM images demonstrated a surface 3D structure with high roughness and composed of interconnected sheets. This newly fabricated 3D sulfur/nitrogen co-doped graphene was used in the simultaneous detection of catechol and hydroquinone with low detection limits of 0.28 and 0.15 μM, respectively. [ABSTRACT FROM AUTHOR]

Graphical abstract The novel electrode materials, NiO ultrathin nanosheets anchored to two types of needle-like NiCo 2 O 4 and slice-like NiCo 2 O 4 on carbon cloth (CC), are synthesized by a simple two-step method. Both as-prepared hierarchical electrodes deliver high specific capacitance and excellent cycling performance, which show the potential of its practical application. Highlights • A new strategy for designing freestanding hierarchical structure of CC/NiCo 2 O 4 @NiO. • The electrodes show high specific capacitance and excellent cycle stability. • The capacitive contributions are leading roles in both kinds of electrodes. • All-solid-state asymmetric supercapacitors deliver high energy and power density. Abstract To fabricate free-standing electrodes with hierarchical structured redox-type metal oxides has become a wise strategy for the development of high-performance energy storage systems. Two types of NiCo 2 O 4 with needle-like and slice-like morphologies act as the conducting cores and hydrothermally grow on carbon cloth (CC/NiCo 2 O 4 -N and CC/NiCo 2 O 4 -S). The mesoporous NiO ultrathin nanosheets further are anchored on the surface of the two types of CC/NiCo 2 O 4 to form the novel high-performance electrodes (CC/NiCo 2 O 4 -N@NiO and CC/NiCo 2 O 4 -S@NiO). Particularly, the formation mechanism of NiO ultrathin nanosheets is proposed. The two integrated electrodes of CC/NiCo 2 O 4 -N@NiO and CC/NiCo 2 O 4 -S@NiO exhibit high specific capacitance of 921.9 and 852.9 mF/cm2 (or 709.1 and 775.1F/g) at 2 mA/cm2, respectively and excellent long cycling lifespan (both 100% retention after 10,000 cycles). The assembled asymmetric supercapacitors, CC/NiCo 2 O 4 -N@NiO//graphene and CC/NiCo 2 O 4 -S@NiO//graphene, can still deliver the high energy density and power density, and possess excellent cycling stability (95.2% and 92.3% retention after 10,000 cycles, respectively). Our work not only provides an attractive strategy and a two-step facile method for construction of hierarchical electrodes based on ultrathin NiO sheets and nanostructured NiCo 2 O 4 , but also offers a strategy for high-performance supercapacitors. [ABSTRACT FROM AUTHOR]

Highlights • A novel NC-Ti 3 C 2 T x hybrid has been synthesized. • NC-Ti 3 C 2 T x hybrid exhibits quick charge/discharge rate up to 3.0 V s−1. • NC-Ti 3 C 2 T x hybrid exhibits higher specific capacitance of 82.8 F g−1 at 1.0 A g−1. • The hybrid exhibits excellent cycling stability (100% retention after 5000 cycles). Abstract The MXenes with excellent chemical and physical properties are novel and promising electrode materials for supercapacitors. However, aggregation and restacking of MXene sheets limit material's electrochemical performance. Here, we report a method to prevent MXene sheets from restacking and significantly improved electrochemical capability of Ti 3 C 2 T x MXene by intercalating with N-doped carbon (NC) introduced from ZIF-8. Ti 3 C 2 T x MXene sheets were prepared by etching Ti 3 AlC 2 powder in HF, then ZIF-8/Ti 3 C 2 T x composite was prepared, followed by annealing in H 2 /Ar atmosphere. Benefited from higher specific surface area and electron conductivity, the obtained NC-Ti 3 C 2 T x hybrid shows the quick charge/discharge rate up to 3.0 V s−1, little IR drop at 50.0 A g−1, higher specific capacitance of 82.8 F g−1 at 1.0 A g−1 (about 210% of the origin), and 100% retention in capacitance after 5000 cycles. This new and effective approach efficiently enhanced the electrochemical performance of Ti 3 C 2 T x MXenes and improved them as one of auspicious electrode materials in future energy storage devices. [ABSTRACT FROM AUTHOR]

Abstract Sandwich-like ZIF-8 nanocrystal derived N-doped carbon decorated graphene sheets are developed through in-situ growth and followed by a thermal annealing treatment. The sandwich-like N-doped carbon decorated graphene sheets (NCGs) contain graphene substrate and the carbon nanoparticles with 30–50 nm in size. The sandwich-like NCGs generate a large specific surface area of 816.4 m2 g−1. With the high surface area and nitrogen doping, the as-fabricated NCGs as electrode materials for supercapacitor exhibit high specific capacitance of 225.0 F g−1 at 0.5 A g−1, an enhanced rate capability and excellent electrochemical stability with 96.8% retention after 10000 cycles even at 10 A g−1. The symmetry supercapacitor based on NCGs delivers an energy density of 12.7 Wh kg−1 at a specific power of 447 W kg−1. When the power density increases to 15126 W kg−1, the energy density can still keep 6.5 W h kg−1. Furthermore, the symmetry supercapacitor shows an excellent cycle stability with 96.6% capacitance retention at 2 A g−1 after 10000 cycles. Graphical abstract Image 1 [ABSTRACT FROM AUTHOR]