Heng-guo Wang

Nitrogen-doped porous graphene with surface decorated MnO2 nanowires as a high-performance anode material for lithium-ion batteries

An effective strategy was developed to prepare a unique composite by growing MnO2 nanowires on the surface of nitrogen-doped porous graphene (MNPG). The nitrogen-doped porous graphene (NPG) can not only be used as a conductive matrix to greatly improve the conductivity of the MnO2 nanowires but also serve as the active material contributing lithium storage capacity to the composite. As expected, when evaluated as an anode material for lithium-ion batteries (LIBs), the MNPGs show a highly stable capacity of up to 1132.4 mA h g−1 after 300 cycles at 0.1 A g−1, a capacity higher than 300 mA h g−1 even after 2400 cycles at 1 A g−1 and a good rate capability of 248.5 mA h g−1 even at 10 A g−1, which might open new avenues for the design of high-performance electrode materials.

One-step facile synthesis of TiO2/Fe2O3 fiber-in-tube hierarchical heterostructures with improved lithium-ion battery performance

We demonstrate a simple, efficient, yet versatile strategy for the synthesis of novel TiO2/Fe2O3 fiber-in-tube hierarchical heterostructures by using a simple electrospinning technique and subsequent annealing. The mechanism for the formation of these controllable structures is investigated. When tested as the anode materials in lithium-ion batteries (LIBs), the TiO2/Fe2O3 fiber-in-tube hierarchical heterostructures not only deliver a high reversible capacity of 987.2 mA h g−1, which is almost quadruple that of the pure TiO2 nanofibers, and 65.1% capacity retention over 240 cycles, but also show excellent rate capability due to the synergetic effect between Fe2O3 and TiO2 as well as the unique features.

Facile synthesis of Co3O4-CeO2 composite oxide nanotubes and their multifunctional applications for lithium ion batteries and CO oxidation

In this study, Co3O4-CeO2 composite oxide nanotubes (CCONs) have been fabricated by using a simple electrospinning technique followed subsequent annealing and their multifunctional applications for lithium ion batteries and CO oxidation have also been investigated for the first time. When utilized as attractive anodes for lithium-ion batteries (LIBs), the CCONs exhibit good rate capability (497.3mAhg-1 at 2Ag-1), high initial capacity (826.2mAhg-1 at 0.05Ag-1) and improved cycling stability (1286.3mAhg-1 after 180 cycles at 0.1Ag-1 and 300.5mAhg-1 with 63.5% retention after 1500 cycles at 1Ag-1). Furthermore, a preliminary CO catalytic oxidation study has demonstrated that the CCONs samples exhibit high catalytic activity. Thus, these properties endorse CCONs as attractive candidates for both LIBs and CO oxidation and this strategy might open new avenues for the design of a series of transition metal oxides with multicomponent for multifunctional applications.

Facile fabrication of Co3O4/nitrogen-doped graphene hybrid materials as high performance anode materials for lithium ion batteries

Novel hybrid materials of well-dispersed Co3O4 nanoparticles with high density anchored on nitrogen-doped graphene (CNGs) are reported. The prepared CNGs show high performance as anode materials for lithium-ion batteries (LIBs), such as high initial discharge capacity (1080.9 mA h g−1 at 50 mA g−1), long cycling stability (a high reversible capacity of 867.9 mA h g−1 after 350 cycles), and high rate capability (155.6 mA h g−1 at 2 A g−1). The high performance arises from the synergetic effect of conductive nitrogen-doped graphene sheets and ultra-small Co3O4 nanoparticles, which highlights the importance of the anchoring of the small sized nanoparticles on the doped graphene sheets for applications in LIBs.

Nitrogen doped carbon nanofiber derived from polypyrrole functionalized polyacrylonitrile for applications in lithium-ion batteries and oxygen reduction reaction

Nitrogen doped carbon nanofiber films (NCNFs) is successfully synthesized via the carbonization of polypyrrole (PPY) functionalized electrospun polyacrylonitrile (PAN) nanofibers. Benefitting from the nitrogen-doped one-dimensional (1D) nanostructure, the as-obtained NCNFs show multifunctional applications as electrode materials for lithium ion batteries (LIBs) and catalysts for oxygen reduction reaction (ORR). For LIB application, the obtained NCNFs could be directly used as flexible, free-standing and binder-free electrode, which exhibits high specific capacity up to 698.9mAhg-1 (higher than that of carbon nanofiber derived from PAN), long life over 160 cycles, and good rate capability (148.8mAhg-1 at 2Ag-1). In addition, a preliminary ORR catalytic activity study has demonstrated that the NCNFs exhibit good catalytic activity. Therefore, these properties endorse NCNFs as auspicious candidates for both LIBs and ORR.

Synthesis of zincphthalocyanine-based conjugated microporous polymers with rigid-linker as novel and green heterogeneous photocatalysts

The novel zincphthalocyanine-based conjugated microporous polymers with rigid-linker (α-ZnPc-CMP and β-ZnPc-CMP) were synthesized by copolymerization of zinc phthalocyanine (ZnPc) and 4, 6-diaminoresorcinol dihydrochloride (DADHC). The α-ZnPc-CMP and β-ZnPc-CMP were utilized as heterogeneous photocatalysts to degrade Rhodamine B (RhB) in aqueous solution. It is the first time for MPc-based CMPs used as heterogeneous photocatalysts for photodegradation of RhB to date. The highly ordered skeletal alignment and two-dimensional open-channel structure of α-ZnPc-CMP and β-ZnPc-CMP not only solve the aggregation of ZnPc and enhance its photocatalytic activity, but also facilitate the recycling and avoid the secondary pollution. The chemical structures and morphologies of α-ZnPc-CMP and β-ZnPc-CMP were well characterized by Fourier transform infrared spectra (FT-IR), solid-state 13C nuclear magnetic resonance (13C NMR), scanning electron microscopy (SEM), N2-sorption/ desorption and X-ray diffraction (XRD). The solubility experiments and thermogravimetric analysis (TGA) showed they have good chemical stability and recyclability. Furthermore, the photocatalytic tests indicated α-ZnPc-CMP and β-ZnPc-CMP have excellent photocatalytic performances for degradation of RhB (3 h, degraded 98 and 97.47%) in the presence of H2O2 under visible-light irradiation. All results reveal that α-ZnPc-CMP and β-ZnPc-CMP have great potential as photocatalysts on the degradation of organic dye contaminants. Moreover, the possible reaction mechanism of α-ZnPc-CMP and β-ZnPc-CMP as photocatalysts for the degradation of RhB is proposed.

Free-standing and flexible organic cathode based on aromatic carbonyl compound/carbon nanotube composite for lithium and sodium organic batteries

Free-standing and flexible organic cathode based on aromatic carbonyl compound/carbon nanotubes (CNTs) has been successfully synthesized by a simple vacuum filtration strategy. The obtained flexible and free-standing film could be directly used as the binder-, additive- and current collector-free cathode for lithium ion batteries (LIBs) and sodium ion batteries (SIBs). Benefitting from the synergistic effect provided by the aromatic carbonyl compound and CNTs, the flexible organic cathode shows excellent lithium and sodium storage properties, including high reversible capacity (∼150 mAh g-1 at 50 mA g-1 for LIBs and 57.8 mAh g-1 at 25 mA g-1 for SIBs), excellent cycling stability (over 500 cycles for LIBs and 300 cycles for SIBs) and good rate capability (48 mAh g-1 even at 2000 mA g-1 for LIBs and 48 mAh g-1 even at 1000 mA g-1 for SIBs). In view of the simple preparation process and excellent performance, the proposed strategy might open new avenues for the design of high-performance flexible organic electrode for the application in energy storage and conversion.

A photo- and thermo-responsive star-shaped diblock copolymer with a porphyrin core prepared via consecutive ATRPs

A star-shaped and diblock copolymer poly(6-[4-(4-methoxyphenylazo)phenoxy]hexylmethacrylate)s-b-poly(N-isopropylacrylamide)s with a zinc-porphyrin core (PAzo-b-PNIPAM) is synthesized via consecutive atom transfer radical polymerizations (ATRPs). The synthesis involves the preparation of the intermediate poly(6-[4-(4-methoxyphenylazo)phenoxy]hexyl methacrylate) with a zinc-porphyrin core (por-PAzo) via ATRP, and then por-PAzo is used as a macroinitiator to polymerize N-isopropylacrylamide (NIPAM) via ATRP to gain PAzo-b-PNIPAM. The structures of the target products are characterized by FT-IR, 1H NMR and UV-vis spectra, and the polydispersity index (PDI) indicates that the molecular weight distribution is narrow and the polymerization is well controlled. Furthermore, the photo- and thermo-responsive properties are also investigated in detail, which demonstrate that the star-shaped diblock copolymer PAzo-b-PNIPAM has a potential application in targeted photodynamic therapy and photo-electro informational storage.

In situ anchoring of metal nanoparticles in the N-doped carbon framework derived from conjugated microporous polymers towards an efficient oxygen reduction reaction

An effective strategy is developed to in situ anchor metal nanoparticles into the nitrogen-doped carbon framework (MNCs) by thermal treatment of metallophthalocyanine based conjugated microporous polymers. The metal nanoparticles are uniformly distributed into the porous nitrogen-doped carbon framework and interact with N active sites, thus showing enhanced diffusion kinetics as catalysts for oxygen reduction reaction. Benefiting from the effective strategy and specific structure, the as-obtained MNCs show superior oxygen reduction reaction activity in both alkaline and acid media, and their long-time stability and methanol tolerance are superior to the commercial Pt–C. Moreover, the MNCs also display high performance as cathode catalysts for Zn–air batteries. In view of the novel synthesis process and excellent performance, the proposed strategy could open new avenues for the design of high-performance oxygen reduction reaction catalysts for energy storage and conversion.