Casting amorphorized SnO2/MoO3 hybrid into foam-like carbon nanoflakes towards high-performance pseudocapacitive lithium storage.

We report an amorphorization-hybridization strategy to enhance lithium storage by casting atomically mixed amorphorized SnO2/MoO3 into porous foam-like carbon nanoflakes (denote as SnO2/MoO3@CNFs, or SMC in short), which are simply prepared by annealing tin(II)/molybdenum(IV) 2-ethylhexanoate within CNFs under ambient atmosphere at a low temperature (300 °C). The SnO2/MoO3 loading amount within CNFs can be easily adjusted by controlling the Sn/Mo/C precursors. When examined as lithium ion battery (LIB) anode materials, the amorphorized SnO2/MoO3@CNFs with carbon content of 32 wt% (also denote as SMC-32, in which the number represents the carbon content) deliver a high reversible capacity of 1120.5 mA h/g after 200 cycles at 200 mA/g and then 651.5 mA h/g after another 300 cycles at 2000 mA/g, which is much better than that of the crystalline SnO2/CNFs (carbon content of 34 wt%), MoO3/CNFs (carbon content of 22.7 wt%), or SnO2/MoO3@CNFs (with lower carbon contents of 11 and 25 wt%). The electrochemical measurements as well as the ex situ structure characterization clearly suggest that combination of amorphorization and hybridization of SnO2/MoO3 with CNFs synergistically contributes to the superior lithium storage performance with high pseudocapacitive contribution.

Integrating TiO2/SiO2 into Electrospun Carbon Nanofibers towards Superior Lithium Storage Performance.

In order to overcome the poor electrical conductivity of titania (TiO2) and silica (SiO2) anode materials for lithium ion batteries (LIBs), we herein report a facile preparation of integrated titania⁻silica⁻carbon (TSC) nanofibers via electrospinning and subsequent heat-treatment. Both titania and silica are successfully embedded into the conductive N-doped carbon nanofibers, and they synergistically reinforce the overall strength of the TSC nanofibers after annealing (Note that titania⁻carbon or silica⁻carbon nanofibers cannot be obtained under the same condition). When applied as an anode for LIBs, the TSC nanofiber electrode shows superior cycle stability (502 mAh/g at 100 mA/g after 300 cycles) and high rate capability (572, 518, 421, 334, and 232 mAh/g each after 10 cycles at 100, 200, 500, 1000 and 2000 mA/g, respectively). Our results demonstrate that integration of titania/silica into N-doped carbon nanofibers greatly enhances the electrode conductivity and the overall structural stability of the TSC nanofibers upon repeated lithiation/delithiation cycling.

Chemical vapor deposition growth of carbon nanotube confined nickel sulfides from porous electrospun carbon nanofibers and their superior lithium storage properties.

Multidimensional architecture design is a promising strategy to explore unique physicochemical characteristics by synergistically integrating different structural and compositional materials. Herein, we report the facile synthesis of a novel dendritic hybrid architecture, where carbon nanotubes (CNTs) with nickel sulfide nanoparticles encapsulated inside are epitaxially grown out of the porous electrospun N-doped carbon nanofibers (CNFs) (denoted as CNT@NS@CNFs) through a combined strategy of electrospinning and chemical vapor deposition (CVD). The adopted thiophene (C4H4S) not only serves as a carbon source for the growth of CNTs but also as a sulfur source for the sulfurization of Ni particles and S-doping into carbon matrices. When examined as an anode material for lithium-ion batteries (LIBs), the dendritic CNT@NS@CNFs display superior lithium storage properties including good cycle stability and high rate capability, delivering a high reversible capacity of 630 mA h g-1 at 100 mA g-1 after 200 cycles and 277 mA h g-1 at a high rate of 1000 mA g-1. These outstanding electrochemical properties can be attributed to the novel hybrid architecture, in which the encapsulation of nickel sulfide nanoparticles within the CNT/CNFs not only efficiently buffers the volume changes upon lithiation/delithiation, but also facilitates charge transfer and electrolyte diffusion owing to the highly conductive networks with open frame structures.

Atomic layer deposition of TiO2 shells on MoO3 nanobelts allowing enhanced lithium storage performance.

Atomic layer deposition (ALD) of TiO2 shells on MoO3 nanobelts (denote as TiO2@MoO3) is realized using a home-made ALD system, which allows a controllable hydrolysis reaction of TiCl4-H2O on an atomic scale. When used as an anode material for lithium ion batteries, the TiO2@MoO3 electrode demonstrates much enhanced lithium storage performance including higher specific capacity, better cycling stability and rate capability.

Waterproof, Ultrahigh Areal-Capacitance, Wearable Supercapacitor Fabrics.

High-performance supercapacitors (SCs) are promising energy storage devices to meet the pressing demand for future wearable applications. Because the surface area of a human body is limited to 2 m2 , the key challenge in this field is how to realize a high areal capacitance for SCs, while achieving rapid charging, good capacitive retention, flexibility, and waterproofing. To address this challenge, low-cost materials are used including multiwall carbon nanotube (MWCNT), reduced graphene oxide (RGO), and metallic textiles to fabricate composite fabric electrodes, in which MWCNT and RGO are alternatively vacuum-filtrated directly onto Ni-coated cotton fabrics. The composite fabric electrodes display typical electrical double layer capacitor behavior, and reach an ultrahigh areal capacitance up to 6.2 F cm-2 at a high areal current density of 20 mA cm-2 . All-solid-state fabric-type SC devices made with the composite fabric electrodes and water-repellent treatment can reach record-breaking performance of 2.7 F cm-2 at 20 mA cm-2 at the first charge-discharge cycle, 3.2 F cm-2 after 10 000 charge-discharge cycles, zero capacitive decay after 10 000 bending tests, and 10 h continuous underwater operation. The SC devices are easy to assemble into tandem structures and integrate into garments by simple sewing.

Facile synthesis of nitrogen and sulfur codoped carbon from ionic liquid as metal-free catalyst for oxygen reduction reaction.

Developing metal-free catalysts for oxygen reduction reaction (ORR) is a great challenge in the development of fuel cells. Nitrogen and sulfur codoped carbon with remarkably high nitrogen content up to 13.00 at % was successfully fabricated by pyrolysis of homogeneous mixture of exfoliated graphitic flakes and ionic liquid 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ([Bimi][Tf2N]). The exfoliated graphite flakes served as a structure-directing substance as well as additional carbon source in the fabrication. It was demonstrated that the use of graphite flakes increased the nitrogen doping level, optimized the composition of active nitrogen configurations, and enlarged the specific surface area of the catalysts. Electrochemical characterizations revealed that the N and S codoped carbon fabricated by this method exhibited superior catalytic activities toward ORR under both acidic and alkaline conditions. Particularly in alkaline solution, the current catalyst compared favorably to the conventional 20 wt % Pt/C catalyst via four-electron transfer pathway with better ORR selectivity. The excellent catalytic activity was mainly ascribed to high nitrogen doping content, appropriate constitution of active nitrogen configurations, large specific surface area, and synergistic effect of N and S codoping.

In situ deposition of Ag-Ag2S hybrid nanoparticles onto TiO2 nanotube arrays towards fabrication of photoelectrodes with high visible light photoelectrochemical properties.

Ag-Ag2S hybrid nanoparticles were deposited onto Anatase anodic TiO2 nanotubular arrays via a one-step in situ hydrothermal method. Characterization was carried out using FE-SEM, HRTEM, XRD, XPS and UV-vis DRS. The fabricated nano-composites exhibit high visible light-sensitivity and photocurrent output as photoanodes in photoelectrochemical applications. The outstanding performance of the final composite is attributed to the surface plasmonic resonance effect of Ag, which is further enhanced by an Ag2S outer-layer.

Electrochemical determination of hydroquinone using hydrophobic ionic liquid-type carbon paste electrodes.

Three types of carbon paste electrodes (CPEs) with different liquid binders were fabricated, and their electrochemical behavior was characterized via a potassium hexacyanoferrate(II) probe. 1-Octyl-3-methylimidazolium hexafluorophosphate ionic liquid (IL) as a hydrophobic conductive pasting binder showed better electrochemical performance compared with the commonly employed binder. The IL-contained CPEs demonstrated excellent electroactivity for oxidation of hydroquinone. A diffusion control mechanism was confirmed and the diffusion coefficient (D) of 5.05 × 10-4 cm2 s-1 was obtained. The hydrophobic IL-CPE is promising for the determination of hydroquinone in terms of high sensitivity, easy operation, and good durability.