Yu-ling Qin

Metal Organic Frameworks Route to in Situ Insertion of Multiwalled Carbon Nanotubes in Co3O4 Polyhedra as Anode Materials for Lithium-Ion Batteries

Hybridizing nanostructured metal oxides with multiwalled carbon nanotubes (MWCNTs) is highly desirable for the improvement of electrochemical performance of lithium-ion batteries. Here, a facile and scalable strategy to fabricate hierarchical porous MWCNTs/Co3O4 nanocomposites has been reported, with the help of a morphology-maintained annealing treatment of carbon nanotubes inserted metal organic frameworks (MOFs). The designed MWCNTs/Co3O4 integrates the high theoretical capacity of Co3O4 and excellent conductivity as well as strong mechanical/chemical stability of MWCNTs. When tested as anode materials for lithium-ion batteries, the nanocomposite displays a high reversible capacity of 813 mAh g(-1) at a current density of 100 mA g(-1) after 100 charge-discharge cycles. Even at 1000 mA g(-1), a stable capacity as high as 514 mAh g(-1) could be maintained. The improved reversible capacity, excellent cycling stability, and good rate capability of MWCNTs/Co3O4 can be attributed to the hierarchical porous structure and the synergistic effect between Co3O4 and MWCNTs. Furthermore, owing to this versatile strategy, binary metal oxides MWCNTs/ZnCo2O4 could also be synthesized as promising anode materials for advanced lithium-ion batteries.

An Efficient Three-Dimensional Oxygen Evolution Electrode†

The challenges of meeting the rapidly increasing global energy demand and developing carbon-neutral economy require untiring efforts to exploit and store abundant but diffuse renewable energy sources. Among many innovative approaches, the efficient production of hydrogen serving as fuel, through electricity-driven water splitting, seems promising and appealing. However, the overall efficiency of the reaction is largely impeded by the kinetically sluggish oxygen evolution reaction (OER), imposing serious overpotential requirement. Although precious metal oxides, such as RuO2 and IrO2, are considered to be the most active OER electrocatalysts, they are not suitable for large-scale applications because of their scarcity and high costs. In response, non-noble transition-metal-based catalysts, especially nickel (Ni), are becoming focus of growing research interests because of their earth-abundant nature and theoretically high catalytic activity. 6] Currently, these non-noble transition-metal-based OER catalysts are usually prepared as thin films from precursor solution containing metal cations by electrodeposition, sputtering, dip-coating, and spin-coating methods on two-dimensional (2D) planar substrates. Although significant improvements have been achieved, the activity and stability of the catalyst layer should be further enhanced by optimizing the structural, mechanical, and electrical contact between the catalyst and the substrates. Compared to the conventional 2D planar architecture, electrodes based on 3D porous materials might improve the activity by increasing the electroactive surface area of the catalysts. Taking the advantages of a comparatively high surface area, high electron conductivity, and low costs, Ni foam is generally chosen to serve as template, support, as well as current collector for battery and supercapacitor. However, the Ni foam cannot be directly used as OER electrode because of its intrinsic instability under the OER experimental condition. In response, constructing protective and conductive interlayers, such as porous carbon, to bridge the outermost oxygen evolution catalyst (OEC) layer and the innermost 3D conductive Ni backbone could be a promising strategy. Other than traditional templates such as mesoprous silica and zeolites, zeolite imidazolate framework (ZIF-8) possesses a high carbon content, high chemical and thermal stability, large Brunauer–Emmett–Teller (BET) surface area, and oxygen-free character, making it a novel and promising template for porous carbon synthesis. To design an efficient OER catalyst with these factors in mind, herein, we first develop a unique approach to fabricate a 3D Ni foam/porous carbon/anodized Ni (NF/PC/AN) electrode, wherein homogeneous coating of the 3D Ni framework with porous carbon membrane plays a key role, which is derived from ZIF-8 and subsequently employed as difunctional interlayer to both protect the inner instable Ni foam and support the outermost Ni OEC layer. It is also the first report that the Ni-based OEC is in situ generated from anodization of the innermost Ni foam skeleton and then penetrated into the voids and finally covered the surface of the porous carbon membrane. Interestingly, the performance of this novel NF/PC/AN electrode is very good for OER, which is considered to be the synergy of the high activity of AN and the high conductivity and stability of the electrode. Briefly, the facile and scalable fabrication process of the 3D NF/PC/AN electrode (see Scheme S1 in the Supporting Information) is described as follows. The Ni foam is first treated with an acid solution containing polyvinylpyrrolidone (PVP) to remove the possible oxide layer and enhance the affinity of the surface. Then, the Ni foam is immersed in methanolic solution of zinc nitrate and 2-methylimidazole to deposit a ZIF-8 membrane. Next, the as-prepared Ni foam/ ZIF-8 is converted to Ni foam/porous carbon under the treatments of calcination in Ar atmosphere and etching the possible Zn species with acid. Finally, anodization is carried out at a constant potential to obtain a 3D NF/PC/AN electrode which can be in situ applied to test the OER activity. The morphology of ZIF-8 supported on a Ni foam skeleton is characterized by scanning electron microscopy (SEM). As shown in Figure 1a,b, the surface of the obtained Ni foam/ZIF-8 is quite different from that of a bare Ni foam (Figure S1), revealing the success of depositing a ZIF-8 membrane on a Ni foam. The ZIF-8 membrane is composed of well intergrown polyhedral crystals with sizes of about 0.2 mm. And no obvious defects such as cracks are observed, indicating the continuous formation of the membrane on the homogeneous support of Ni foam. From the cross-sectional view (Figure 1c), the thickness of the ZIF-8 membrane is measured to be about 4.5 mm. The carbonization of the ZIF-8 membrane is carried out by calcinating the Ni foam/ZIF-8 at 800 8C for 5 h at a heating rate of 3 8Cmin 1 in Ar atmosphere. Although the carbonization temperature is close to the [*] J. Wang, H. X. Zhong, Y. L. Qin, Prof. X. B. Zhang State Key Laboratory of Rare Earth Resource Utilization Changchun Institute of Applied Chemistry Chinese Academy of Sciences, Changchun, 130022 (P.R. China) E-mail: xbzhang@ciac.jl.cn Homepage: http://energy.ciac.jl.cn

In situ synthesis of magnetically recyclable graphene-supported Pd@Co core–shell nanoparticles as efficient catalysts for hydrolytic dehydrogenation of ammonia borane

Graphene supported Pd@Co core–shell nanocatalysts with magnetically recyclability were synthesized via the in situ synthesis strategy utilizing the distinction in reduction potentials of the two precursors with appropriate reductant. The as-synthesized catalysts exerted satisfied catalytic activity (916 L mol−1 min−1) and recycle stability for hydrolytic dehydrogenation of ammonia borane.

Rapid and shape-controlled synthesis of "clean" star-like and concave Pd nanocrystallites and their high performance toward methanol oxidation

Uniform “clean” star-shaped and concave palladium (Pd) nanocrystallites (NCs) are first successfully synthesized via a very simple and rapid route without using any surfactants. Interestingly, the as-prepared Pd NCs manifest superior electrocatalytic activity and stability toward methanol oxidation over the commercial Pd/C catalyst.

Coated/Sandwiched rGO/CoSx Composites Derived from Metal-Organic Frameworks/GO as Advanced Anode Materials for Lithium-Ion Batteries.

Rational composite materials made from transition metal sulfides and reduced graphene oxide (rGO) are highly desirable for designing high-performance lithium-ion batteries (LIBs). Here, rGO-coated or sandwiched CoSx composites are fabricated through facile thermal sulfurization of metal-organic framework/GO precursors. By scrupulously changing the proportion of Co(2+) and organic ligands and the solvent of the reaction system, we can tune the forms of GO as either a coating or a supporting layer. Upon testing as anode materials for LIBs, the as-prepared CoSx -rGO-CoSx and rGO@CoSx composites demonstrate brilliant electrochemical performances such as high initial specific capacities of 1248 and 1320 mA h g(-1) , respectively, at a current density of 100 mA g(-1) , and stable cycling abilities of 670 and 613 mA h g(-1) , respectively, after 100 charge/discharge cycles, as well as superior rate capabilities. The excellent electrical conductivity and porous structure of the CoSx /rGO composites can promote Li(+) transfer and mitigate internal stress during the charge/discharge process, thus significantly improving the electrochemical performance of electrode materials.

Sulfur-impregnated core-shell hierarchical porous carbon for lithium-sulfur batteries.

Core-shell hierarchical porous carbon spheres (HPCs) were synthesized by a facile hydrothermal method and used as host to incorporate sulfur. The microstructure, morphology, and specific surface areas of the resultant samples have been systematically characterized. The results indicate that most of sulfur is well dispersed over the core area of HPCs after the impregnation of sulfur. Meanwhile, the shell of HPCs with void pores is serving as a retard against the dissolution of lithium polysulfides. This structure can enhance the transport of electron and lithium ions as well as alleviate the stress caused by volume change during the charge-discharge process. The as-prepared HPC-sulfur (HPC-S) composite with 65.3 wt % sulfur delivers a high specific capacity of 1397.9 mA h g(-1) at a current density of 335 mA g(-1) (0.2 C) as a cathode material for lithium-sulfur (Li-S) batteries, and the discharge capacity of the electrode could still reach 753.2 mA h g(-1) at 6700 mA g(-1) (4 C). Moreover, the composite electrode exhibited an excellent cycling capacity of 830.5 mA h g(-1) after 200 cycles.

Controllable synthesis of cube-like ZnSnO3@TiO2 nanostructures as lithium ion battery anodes

ZnSnO3 is an attractive anode material for lithium ion batteries because of its higher theoretical capacity compared to the state-of-the-art carbonaceous counterpart. The main challenges associated with ZnSnO3 anodes are structural degradation and instability of the solid-electrolyte interphase, caused by the large volume change during cycling. Herein, we propose a hierarchical structured ZnSnO3@TiO2 nanocomposite anode that tackles this problem. The as-prepared, core–shell, cube-like anode material exhibits enhanced capacity and cycling property. In proof-of-concept experiments, this hierarchical heterostructure shows a high initial discharge capacity of 1590 mA h g−1 at 100 mA g−1 and retained 780 mA h g−1 after 200 cycles, which is much better than the anodes made of pure ZnSnO3 nanomaterials. The enhanced cycle life can be attributed to the reductive volume expansion during the repeated charge–discharge cycles, owing to the hierarchical porous three-dimensional structure and TiO2 shell as well as the synergistic effects of ZnSnO3 and TiO2.

Preparation of Pd-Co-Based Nanocatalysts and Their Superior Applications in Formic Acid Decomposition and Methanol Oxidation

Formic acid (FA) and methanol, as convenient hydrogen-containing materials, are most widely used for fuel cells. However, using suitable and low-cost catalysts to further improve their energy performance still is a matter of great significance. Herein, PdCo and PdCo@Pd nanocatalysts (NCs) are successfully prepared by the facile method. Pd 3d binding energy decreases due to the presence of Co. Consequently, PdCo@Pd NCs exhibit high catalytic activity and selectivity toward FA dehydrogenation at room temperature. The gas-generation rate at 30 min is 65.4 L h(-1)  g(-1) . PdCo/C has the worst catalytic performance in this reaction, despite the fact that it has a high gas-generation rate in the initial 30 min. Furthermore, both PdCo and PdCo@Pd NCs have enhanced electrocatalytic performance toward methanol oxidation. Their maximum currents are 966 and 1205 mA mg(-1) , respectively, which is much higher than monometallic Pd/C.

Improved hydrogen production from formic acid under ambient conditions using a PdAu catalyst on a graphene nanosheets–carbon black support

Formic acid (FA) has great potential as a suitable liquid source for hydrogen and hydrogen storage materials, provided highly active and selective dehydrogenation catalysts under ambient conditions are developed. Here, well-dispersed bimetallic gold–palladium (PdAu) nanoparticles (NPs) grown on graphene nanosheets–carbon black (GNs–CB) composite supports are synthesized via a facile co-reduction method, wherein the GNs–CB composite support proved to be a powerful dispersion agent and a distinct support for the PdAu NPs. Interestingly, the resultant PdAu/GNs–CB catalyst manifests high selectivity and exceedingly high activity to complete the decomposition of FA at room temperature.

Solvothermal synthesis of GO/V2O5 composites as a cathode material for rechargeable magnesium batteries

Herein GO/V2O5 composites as a cathode material for rechargeable magnesium batteries are presented. Synthesized by the solvothermal reaction of vanadium oxytriisopropoxide (VOT) and graphene oxide (GO), the GO/V2O5 composites exhibit greatly enhanced electrochemical performances, and attained a high discharge capacity up to 178 mAh g−1 at a rate of 0.2C.