Yue-E Miao

High-performance supercapacitors based on hollow polyaniline nanofibers by electrospinning.

Hollow polyaniline (PANI) nanofibers with controllable wall thickness are fabricated by in situ polymerization of aniline using the electrospun poly(amic acid) fiber membrane as a template. A maximum specific capacitance of 601 F g(-1) has been achieved at 1 A g(-1), suggesting the potential application of hollow PANI nanofibers for supercapacitors. The superior electrochemical performance of the hollow nanofibers is attributed to their hollow structure, thin wall thickness, and orderly pore passages, which can drastically facilitate the ion diffusion and improve the utilization of the electroactive PANI during the charge-discharge processes. Furthermore, the high flexibility of the self-standing fiber membrane template provides possibilities for the facile construction and fabrication of conducting polymers with hollow nanostructures, which may find potential applications in various high-performance electrochemical devices.

Biomass-Derived Nitrogen-Doped Carbon Nanofiber Network: A Facile Template for Decoration of Ultrathin Nickel-Cobalt Layered Double Hydroxide Nanosheets as High-Performance Asymmetric Supercapacitor Electrode.

The development of biomass-based energy storage devices is an emerging trend to reduce the ever-increasing consumption of non-renewable resources. Here, nitrogen-doped carbonized bacterial cellulose (CBC-N) nanofibers are obtained by one-step carbonization of polyaniline coated bacterial cellulose (BC) nanofibers, which not only display excellent capacitive performance as the supercapacitor electrode, but also act as 3D bio-template for further deposition of ultrathin nickel-cobalt layered double hydroxide (Ni-Co LDH) nanosheets. The as-obtained CBC-N@LDH composite electrodes exhibit significantly enhanced specific capacitance (1949.5 F g(-1) at a discharge current density of 1 A g(-1) , based on active materials), high capacitance retention of 54.7% even at a high discharge current density of 10 A g(-1) and excellent cycling stability of 74.4% retention after 5000 cycles. Furthermore, asymmetric supercapacitors (ASCs) are constructed using CBC-N@LDH composites as positive electrode materials and CBC-N nanofibers as negative electrode materials. By virtue of the intrinsic pseudocapacitive characteristics of CBC-N@LDH composites and 3D nitrogen-doped carbon nanofiber networks, the developed ASC exhibits high energy density of 36.3 Wh kg(-1) at the power density of 800.2 W kg(-1) . Therefore, this work presents a novel protocol for the large-scale production of biomass-derived high-performance electrode materials in practical supercapacitor applications.

Ni-Doped Graphene/Carbon Cryogels and Their Applications As Versatile Sorbents for Water Purification

Ni-doped graphene/carbon cryogels (NGCC) have been prepared by adding resorcinol and formaldehyde to suspension of graphene oxide (GO), using Ni(2+) ions as catalysts for the gelation process to substitute the usually used alkaline carbonates. The metal ions of Ni(2+) have elevated the cross-linking between GO and RF skeletons, thus strengthening the whole cryogel. The as-formed three-dimensional (3D) interconnected structures, which can be well-maintained after freeze-drying of the hydrogel precursor and subsequent carbonization under an inert atmosphere, exhibit good mechanical properties. During the carbonization process, Ni(2+) ions are converted into Ni nanoparticles and thus embedded in the interconnected structures. The unique porosity within the interconnected structures endows the cryogels with good capability for the extraction of oils and some organic solvents while the bulk form enables its recycling use. When ground into powders, they can be used as adsorbents for dyestuffs. Therefore, the as-obtained cryogels may find potential applications as versatile candidates for the removal of pollutants from water.

Electrospun carbon nanofibers decorated with Ag-Pt bimetallic nanoparticles for selective detection of dopamine.

Electrospun nanoporous carbon nanofibers (pCNFs) decorated with Ag-Pt bimetallic nanoparticles have been successfully synthesized by combining template carbonization and seed-growth reduction approach. Porous-structured polyacrylonitrile (PAN) nanofibers (pPAN) were first prepared by electrospinning PAN/polyvinylpyrrolidone (PVP) blend solution, followed by subsequent water extraction and heat treatment to obtain pCNFs. Ag-Pt/pCNFs were then obtained by using pCNFs as support for bimetallic nanoparticle loading. Thus, the obtained Ag-Pt/pCNFs were used to modify glassy carbon electrode (GCE) for selective detection of dopamine (DA) in the presence of uric acid (UA) and ascorbic acid (AA). This novel sensor exhibits fast amperometric response and high sensitivity toward DA with a wide linear concentration range of 10-500 μM and a low detection limit of 0.11 μM (S/N = 3), wherein the interference of UA and AA can be eliminated effectively.

Electrospun Self-Standing Membrane of Hierarchical SiO2@γ-AlOOH (Boehmite) Core/Sheath Fibers for Water Remediation

Hierarchical SiO(2)@γ-AlOOH (Boehmite) core/sheath fibers are fabricated based on a combination of electrospinning and hydrothermal reaction. γ-AlOOH (Boehmite) nanoplatelets are uniformly anchored on the surface of SiO(2) fibers, which significantly improves the adsorption efficiency of the SiO(2) fiber membrane for organic dyes and microorganisms. Compared to conventional nanoparticle adsorbents, the self-standing membrane thus prepared is highly flexible and easy to handle and retrieve, making it a promising material for water treatment. By virtue of electrospinning and a hydrothermal reaction, it provides possibilities to fabricate other functional fiber membranes with hierarchical structures, which can find potential applications in adsorption, catalysis, filtration, and other environmental remediation fields.

Flexible Hybrid Membranes with Ni(OH)2 Nanoplatelets Vertically Grown on Electrospun Carbon Nanofibers for High-Performance Supercapacitors

The practical applications of transition metal oxides and hydroxides for supercapacitors are restricted by their intrinsic poor conductivity, large volumetric expansion, and rapid capacitance fading upon cycling, which can be solved by optimizing these materials to nanostructures and confining them within conductive carbonaceous frameworks. In this work, flexible hybrid membranes with ultrathin Ni(OH)2 nanoplatelets vertically and uniformly anchored on the electrospun carbon nanofibers (CNF) have been facilely prepared as electrode materials for supercapacitors. The Ni(OH)2/CNF hybrid membranes with three-dimensional macroporous architectures as well as hierarchical nanostructures can provide open and continuous channels for rapid diffusion of electrolyte to access the electrochemically active Ni(OH)2 nanoplatelets. Moreover, the carbon nanofiber can act both as a conductive core to provide efficient transport of electrons for fast Faradaic redox reactions of the Ni(OH)2 sheath, and as a buffering matrix to mitigate the local volumetric expansion/contraction upon long-term cycling. As a consequence, the optimized Ni(OH)2/CNF hybrid membrane exhibits a high specific capacitance of 2523 F g(-1) (based on the mass of Ni(OH)2, that is 701 F g(-1) based on the total mass) at a scan rate of 5 mV s(-1). The Ni(OH)2/CNF hybrid membranes with high mechanical flexibility, superior electrical conductivity, and remarkably improved electrochemical capacitance are condsidered as promising flexible electrode materials for high-performance supercapacitors.

Hierarchical ZnCo2O4@NiCo2O4 Core–Sheath Nanowires: Bifunctionality towards High-Performance Supercapacitors and the Oxygen-Reduction Reaction

Increasing energy demands and worsening environmental issues have stimulated intense research on alternative energy storage and conversion systems including supercapacitors and fuel cells. Here, a rationally designed hierarchical structure of ZnCo2 O4 @NiCo2 O4 core-sheath nanowires synthesized through facile electrospinning combined with a simple co-precipitation method is proposed. The obtained core-sheath nanostructures consisting of mesoporous ZnCo2 O4 nanowires as the core and uniformly distributed ultrathin NiCo2 O4 nanosheets as the sheath, exhibit excellent electrochemical activity as bifunctional materials for supercapacitor electrodes and oxygen reduction reaction (ORR) catalysts. Compared with the single component of either ZnCo2 O4 nanowires or NiCo2 O4 nanosheets, the hierarchical ZnCo2 O4 @NiCo2 O4 core-sheath nanowires demonstrate higher specific capacitance of 1476 F g(-1) (1 A g(-1) ) and better rate capability of 942 F g(-1) (20 A g(-1) ), while maintaining 98.9 % capacity after 2000 cycles at 10 A g(-1) . Meanwhile, the ZnCo2 O4 @NiCo2 O4 core-sheath nanowires reveal comparable catalytic activity but superior stability and methanol tolerance over Pt/C as ORR catalyst. The impressive performance may originate from the unique hierarchical core-sheath structures that greatly facilitate enhanced reactivity, and faster ion and electron transfer.

Electrically Conductive Polyaniline/Polyimide Nanofiber Membranes Prepared via a Combination of Electrospinning and Subsequent In situ Polymerization Growth

Highly aligned polyimide (PI) nanofiber membranes have been prepared by electrospinning equipped with a high speed rotating collector. As the electrospun polyimide nanofiber membranes possess large surface area, they can be used as the template for in situ growth of polyaniline (PANi) by using FeCl₃ as the oxidant. It is found that PANi nanoparticles can be uniformly distributed on the surface of highly aligned PI nanofibers due to the low oxidization/reduction potential of FeCl₃ and the active nucleation sites of the functionalized PI nanofibers. The as-prepared PANi/PI composite membranes not only possess excellent thermal and mechanical properties but also show good electrical conductivity, pH sensitivity and significantly improved electromagnetic impedance properties. This is a facile method for fabricating high-performance and multifunctional composites that can find potential applications in electrical and aerospace fields.

Morphology and Photocatalytic Property of Hierarchical Polyimide/ZnO Fibers Prepared via a Direct Ion-exchange Process

A simple and efficient method has been developed for preparing hierarchical nanostructures of polyimide (PI)/ZnO fibers by combining electrospinning and direct ion-exchange process. Poly(amic acid) (PAA) nanofibers are first prepared by electrospinning, and then, the electrospun PAA fibers are immersed into ZnCl2 solution. After a subsequent thermal treatment, imidization of PAA and formation of ZnO nanoparticles can be simultaneously achieved in one step to obtain PI/ZnO composite fibers. SEM images show that ZnO nanoparticles are densely and uniformly immobilized on the surface of electrospun PI fibers. Furthermore, the morphology of ZnO can be tuned from nanoplatelets to nanorods by changing the initial concentration of ZnCl2 solution. Photocatalytic degradation tests show an efficient degradation ability of PI/ZnO composite membranes toward organic dyes. Meanwhile, the free-standing membrane is highly flexible, easy to handle, and easy to retrieve, which enables its use in water treatment. This simple and inexpensive approach can also be applied to fabricating other hierarchically nanostructured composites.

Perpendicularly oriented few-layer MoSe2 on SnO2 nanotubes for efficient hydrogen evolution reaction

Maximizing the number of exposed active edges in newly emerged two-dimensional few-layer MoSe2 nanostructures is a key issue to fully realize the excellent electrochemical properties of MoSe2. In this work, a SnO2@MoSe2 nanostructure was successfully fabricated through a facile electrospinning technique combined with sintering and a solvothermal method. This rationally designed hierarchical architecture has perpendicularly oriented few-layered MoSe2 nanosheets uniformly and fully covering both inner and outer surfaces of SnO2 nanotubes, which exhibits excellent electrochemical activity as a hydrogen evolution reaction (HER) catalyst with a small onset potential of −0.11 V vs. reversible hydrogen electrode (RHE) and a small Tafel slope of 51 mV per decade. This excellent performance may originate from the unique hierarchical tubular structure with fully exposed active edges and open spaces for fast electron/electrolyte transfer, enabling their potential to replace Pt as a future electrocatalyst in HER.