Lixue Zhang

Synthesis of Nitrogen-Doped MnO/Graphene Nanosheets Hybrid Material for Lithium Ion Batteries

Nitrogen-doped MnO/graphene nanosheets (N-MnO/GNS) hybrid material was synthesized by a simple hydrothermal method followed by ammonia annealing. The samples were systematically investigated by X-ray diffraction analysis, Raman spectroscopy, X-ray photoelectron spectroscopy, transmission electron microscopy, and atomic force microscopy. N-doped MnO (N-MnO) nanoparticles were homogenously anchored on the thin layers of N-doped GNS (N-GNS) to form an efficient electronic/ionic mixed conducting network. This nanostructured hybrid exhibited a reversible electrochemical lithium storage capacity as high as 772 mAh g(-1) at 100 mA g(-1) after 90 cycles, and an excellent rate capability of 202 mA h g(-1) at a high current density of 5 A g(-1). It is expected that N-MnO/GNS hybrid could be a promising candidate material as a high capacity anode for lithium ion batteries.

Graphene oxide nanosheets/multi-walled carbon nanotubes hybrid as an excellent electrocatalytic material towards VO2+/VO2+ redox couples for vanadium redox flow batteries

A graphene oxide nanosheets/multi-walled carbon nanotubes (GO/MWCNTs) hybrid with excellent electrocatalytic redox reversibility towards VO2+/VO2+ redox couples for vanadium redox flow batteries (VRFB) has been prepared by an electrostatic spray technique after efficient ultrasonic treatment. The structures and electrochemical properties of GO/MWCNTs are investigated by transmission electron microscopy, scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, Raman spectroscopy and cyclic voltammetry. GO/MWCNTs are shown to be cross-linked and form an electrocatalytic hybrid with an effective mixed conducting network, leading to efficiently fast ion and electron transport characteristics. Compared with the pure GO nanosheets and MWCNTs, GO/MWCNTs deliver a much better electrocatalytic redox reversibility towards the positive VO2+/VO2+ couple, especially for the reduction from VO2+ to VO2+. The excellent experimental results demonstrate that the newly developed hybrid material holds great promise in the application of VRFB.

Mesoporous NiCo2O4 nanoflakes as electrocatalysts for rechargeable Li–O2 batteries

Herein, we report the facile synthesis of mesoporous NiCo(2)O(4) nanoflakes and their application in nonaqueous Li-O(2) batteries as cathode catalysts. The assembled Li-O(2) batteries presented lower overpotentials and enhanced cyclability, which should be attributed to the superior electrocatalytic activity and the mesoporous nanostructure of NiCo(2)O(4).

Molybdenum nitride based hybrid cathode for rechargeable lithium-O2 batteries

Molybdenum nitride/nitrogen-doped graphene nanosheets (MoN/NGS) are synthesized and used as an alternative O(2) electrode for Li-O(2) batteries. In comparison with electrocatalysts proposed previously, this hybrid cathode exhibits a high discharge potential (around 3.1 V) and a considerable specific capacity (1490 mA h g(-1), based on carbon + electrocatalyst).

Nanostructured Titanium Nitride/PEDOT:PSS Composite Films As Counter Electrodes of Dye-Sensitized Solar Cells

The composite films of titanium nitride in conjunction with polystyrenesulfonate-doped poly (3,4-ethylene-dioxythiophene) (PEDOT:PSS) were prepared by a simple mechanical mixture of TiN and PEDOT:PSS under ultrasonication, which was demonstrated to deliver an effectively combined network of both high electrical conductivity and superior electrocatalytic activity. The composite films have been explored as an alternative for the counter electrodes of dye-sensitized solar cells. It was manifested that these nanostructured TiN-PEDOT:PSS composite films displayed excellent performance comparable to Pt-FTO counter electrode due to the combined network endowing more favorable and efficient interfacial active sites. Among them, the energy conversion efficiency of the cell with TiN(P)-PEDOT:PSS as counter electrode reached 7.06%, which was superior to 6.57% of the cell with Pt-FTO counter electrode under the same experimental conditions.

One-step, solution-processed formamidinium lead trihalide (FAPbl((3-x))Cl(x)) for mesoscopic perovskite-polymer solar cells

Formamidinium (FA) lead triiodide perovskite with chlorine addition (NH2CH=NH2PbI(3-x)Clx) is employed as a light harvester in mesoscopic solar cells for the first time. It is demonstrated that a phase-pure FAPbI(3-x)Clx perovskite layer can be synthesized using a one-step solution-process at 140 °C, and the resultant solar cells deliver a maximum power conversion efficiency of 7.51%, which is the most efficient formamidinium-lead-halide perovskite mesoscopic solar cell employing a polymer hole-transporting layer. The effects of the thermal annealing temperature on the quality/morphology of the perovskite layer and the solar cells performance are discussed. The advantages offered by the one-step solution-processing method and the reduced bandgap make FAPbI(3-x)Clx perovskites an attractive choice for future hybrid photovoltaics.

Molybdenum nitride/n-doped carbon nanospheres for lithium-o2 battery cathode electrocatalyst.

Molybdenum nitride/N-doped carbon nanospheres (MoN/N-C) are synthesized by hydrothermal method followed by ammonia annealing. The as-prepared MoN/N-C nanospheres manifest considerable electrocatalytic activity toward oxygen reduction reaction in nonaqueous electrolytes because of its nanostructure and the synergetic effect between MoN and N-C. Furthermore, the MoN/N-C nanospheres are explored as cathode catalyst for Li-O2 batteries with tetra-(ethylene glycol) dimethyl ether as the electrolyte. The assembled batteries deliver alleviated overpotentials and improved battery lifespan, and their excellent performances should be attributed to the unique hierarchical structure and high fraction of surface active sites of cathode catalyst.

Compatible interface design of CoO-based Li-O 2 battery cathodes with long-cycling stability

Lithium-oxygen batteries with high theoretical energy densities have great potential. Recent studies have focused on different cathode architecture design to address poor cycling performance, while the impact of interface stability on cathode side has been barely reported. In this study, we introduce CoO mesoporous spheres into cathode, where the growth of crystalline discharge products (Li2O2) is directly observed on the CoO surface from aberration-corrected STEM. This CoO based cathode demonstrates more than 300 discharge/charge cycles with excessive lithium anode. Under deep discharge/charge, CoO cathode exhibited superior cycle performance than that of Co3O4 with similar nanostructure. This improved cycle performance can be ascribed to a more favorable adsorption configuration of Li2O2 intermediates (LiO2) on CoO surface, which is demonstrated through DFT calculation. The favorable adsorption of LiO2 plays an important role in the enhanced cycle performance, which reduced the contact of LiO2 to carbon materials and further alleviated the side reactions during charge process. This compatible interface design may provide an effective approach in protecting carbon-based cathodes in metal-oxygen batteries.

Oxygen-enriched carbon material for catalyzing oxygen reduction towards hybrid electrolyte Li-air battery

Graphene oxide, with sufficient oxygen-containing groups, is integrated with electronically conductive carbon nanotubes to be explored as an efficient metal-free catalyst for the oxygen reduction reaction. Preliminary theoretical calculations with the density functional theory method indicate that the existence of graphene oxide is favorable for the adsorption and subsequent four-electron reduction reactions of O2. Furthermore, this oxygen-enriched hybrid material was tested as a cathode in aprotic/aqueous hybrid electrolyte Li-air batteries. The hybrid material exhibited a very low overpotential (the voltage gap at 0.1 mA cm−2 is only 0.17 V) and better electrocatalytic performance owing to abundant oxygen containing groups and its excellent electroconductivity. These experimental and theoretical demonstrations should provide an important mechanistic insight into carbon-based metal-free catalysts in fuel cells and metal-air battery applications. We believe that the demonstrations shown in this paper provide a promising strategy to investigate highly efficient metal-free catalysts for advanced energy devices.

1D coaxial platinum/titanium nitride nanotube arrays with enhanced electrocatalytic activity for the oxygen reduction reaction: towards Li-air batteries.

CAT ON A HOT TIN SUPPORT: Coaxial Pt/TiN nanotube arrays are used to achieve a superior electrocatalytic activity of platinum towards the oxygen reduction reaction (ORR). Compared to a commercial Pt/C catalyst, the Pt/TiN NTA materials delivers a higher mass activity and specific activity for the ORR. Hence, these materials are useful as cathodes for hybrid electrolyte Li-air batteries, as demonstrated.