Ni3+ -Rich Ni/NiOx @C Nanocapsules Below 4 nm Constructed by Low-Temperature Graphitization of Self-Assembled Few-Layer Coordination Polymers toward Efficient Alkaline Hydrogen Evolution Electrocatalysis.

Low-cost and eco-friendly Ni/NiO heterojunctions have been theoretically proven to be the ideal candidate for stepwise electrocatalysis of alkaline hydrogen evolution reaction, attributed to the preferred OHad adsorption by incompletely filled d orbitals of NiO phase and favorable Had adsorption energy of Ni phase. Nevertheless, most Ni/NiO compounds reported so far fail to exhibit excellent catalytic activity, possibly due to the lack of efficient electron transport, limited interfacial active sites, and unregulated Nin+ ratios. To address the above bottlenecks, herein, the ultrasmall Ni/NiOx @C nanocapsules (<5 nm) are directly constructed by graphitization of four-layer Ni-based coordination polymers at record low temperatures of 400 °C. Ascribed to the accelerated electron and mass transfer by the carbon nano-onions coated around Ni/NiOx heterojunctions, the extreme rise in interfaces and Ni3+ defects with t6 2ge1 g electronic configuration owed to the ultrasmall size, the Ni/NiOx @C nanocapsules exhibit the highest catalytic activity and the lowest overpotential of η10 = 80 mV among various Ni/NiO materials (measured on the glassy carbon electrode). This work not only constructs an industrialized high-efficiency electrocatalyst toward alkaline HER, but also provides a novel strategy for the constant-scale preparation of multicomponent transition metals-based nanocrystals below 4 nm.

Ni/NiO@NC as a highly efficient and durable HER electrocatalyst derived from nickel(II) complexes: importance of polydentate amino-acid ligands.

Research on Ni/NiO electrocatalysts has advanced significantly, but the main obstacles to their use and commercialization remain their relatively ordinary activity and stability. In this paper, a chelating structure based on the coordination of multidentate ligands and Ni(II) is proposed to limit the growth of Ni and Ni oxide grains. These features reduce the particle size of Ni/NiO, increase particle dispersion, and maintain the high activity and stability of the catalyst. Aspartic acid, as a polydentate ligand, could coordinate with Ni2+ to form structurally stable chelate rings. The latter can limit grain growth, but also coat the active core with thin carbon layers after calcination to further achieve the confinement and protection of nanoparticles. The hydrogen evolution overpotential of prepared nitrogen-doped graphitized carbon shells (Ni/NiO@NC) nanoparticles was 100 mV (vs. RHE) when the current density was 10 mA cm-2 in 1 M KOH. The hydrogen evolution overpotential increased by only 4 mV after 6000 continuous cyclic-voltammetry scans. Moreover, when coated on different conductive substrates, the overpotential of this catalyst dropped to 34.6 mV (vs. RHE) at a current density of 10 mV cm-2. The lowest overpotential of the composite was only 194.9 mV at a current density of 100 mA cm-2, which is comparable with that of noble metal-based electrocatalysts. This work provides a plausible method for designing high-performance electrocatalysts of small size.

Built-in electric field boosted ionic transport kinetics in the heterostructured ZnCo2O4/ZnO nanobelts for high-performance supercapacitor.

Metal oxides are promising electrode candidates for supercapacitor due to their high theoretical capacitance, good reversibility, and low cost. However, they show inferior specific capacitance and power density because of their sluggish ion diffusion kinetics and intrinsically poor electrical conductivity within the solid phase. Herein, heterostructured ZnCo2O4/ZnO nanobelts are successfully prepared by using self-assembled Zn/Co-based nanosized coordination polymers as the precursors. The resulted nanobelts are composed of uniformly distributed ZnCo2O4 and ZnO nanocrystals, which spontaneously develop built-in electric fields in the nanobelts, and thus improve the conductivity and accelerate charge transport. The as-obtained ZnCo2O4/ZnO nanobelts display a high specific capacitance of 481.0 F g-1 at 1 A/g. The asymmetric supercapacitor, with a ZnCo2O4/ZnO positive electrode and an activated carbon negative electrode, deliver an energy of 23.77 Wh kg-1 at the power density of 399.98 W kg-1 and excellent prolonged cycle life. The excellent electrochemical performance benefits from both the special structure and built-in field at the heterostructure interface, which could significantly reduce the ion diffusion resistance and thus promote charge transport. This strategy may blaze a trail for engineering efficient electrode based on earth-abundant materials.

Facile assembly of 2D Ni-based coordination polymer nanosheets as battery-type electrodes for high-performance supercapacitors.

Large-scale Ni-based nano-sized coordination polymers (Ni-nCPs) are facilely constructed by a self-assembled approach at room temperature and atmosphere pressure. In this strategy, we use only the environmentally friendly solvents of water and ethanol, and the synthesis of 2D Ni-nCPs via a self-assembly route appears close to the "green chemistry" concept. In addition, the morphologies of the Ni-nCPs can be easily adjusted by the water/ethanol ratio. Owing to its unique 2D ultrathin nature and large specific surface area, Ni-nCPs-1 achieves a great number of channels for the transport of electrons and ions and electrochemically redox active sites for a faradaic reaction. Therefore, battery-type Ni-nCPs-1 electrodes have a bright prospect in energy storage, and can reach an outstanding specific capacitance value as high as 1066.9 F g-1 at 1 A g-1. Additionally, the asymmetric supercapacitor (Ni-nCPs-1//active carbon) displays a high energy density of 47.9 W h kg-1 at a power density of 440 W kg-1 and an excellent long-term cycle stability. This work may open up a new path in advanced electrode materials for efficient and real-time energy storge applications.

From coordination polymers to nanocrystals: general and facile synthesis of ultra-small metal oxide nanocrystals.

A facile and general strategy for the large-scale synthesis of ultrasmall metal oxide nanocrystals with particle size of about 2 nm was proposed using coordination polymers (CPs) as templates.

Construction of magnetic NiO/C nanosheets derived from coordination polymers for extraordinary adsorption of dyes.

Herein, a facial stratagem for the large-scale synthesis of NiO/C nanosheets used as magnetic adsorbents is proposed by using nanoscale coordination polymers (nanoCPs) as precursors. The NiO nanoparticles (NPs) scattered on the NiO/C nanosheets have an untrasmall size (~3 nm) as well as uniform dispersion, since the Ni2+ ions are preassembled into the nanoCPs precursors by coordination bonds and transformed to NiO NPs in situ under the restriction of carbon layers. Thanks to the small size and spatially uniform distribution of NiO NPs, fully exposed carbon matrix containing part of graphene structures, and the high specific surface area of the special nanosheet structure, the magnetic NiO/C nanosheets have an a great breakthrough in the adsorption performance toward Congo Red (CR) among many reported NiO-based materials. The maximum adsorption capacity for CR is up to 2000 mg/g, and the adsorption kinetics and thermodynamics are also systematically studied. Moreover, the NiO/C nanosheets can be separated from water and reused simply by an external magnetic field. The NiO/C nanosheets with low cost and extraordinary adsorption ability have great potential in water pollution treatment area.

A general autocatalytic route toward silica nanospheres with ultrasmall sized and well-dispersed metal oxide nanoparticles.

A facile and efficient approach for the synthesis of metal ions@silica nanospheres is proposed by using an intramolecular autocatalytic route. By the rational selection of reactants, metal ions@silica nanospheres can be obtained via successive spontaneous reactions under near neutral conditions. After thermal treatment, spherical silica equipped with ultrasmall and highly dispersed metal oxides nanoparticles was obtained.

Directed self-assembly of dual metal ions with ligands: towards the synthesis of noble metal/metal oxide composites with controlled facets.

The large-scale synthesis of noble metal/metal oxide spheres with controlled facets was for the first time enabled by making use of a bottom-up self-assembly strategy.

The development of novel Au/CaO nanoribbons from bifunctional building block for biodiesel production.

Herein, a novel and facile high-yield strategy is reported to efficiently fabricate 1D self-supported Au/CaO nanocatalysts using dual metal co-ordination polymers as templates. Significantly, a uniform distribution of dual metal nanoparticles can be ensured due to the fact that both Ca2+ and Au3+ ions are initially introduced into the co-ordination polymer via chemical bonding with bifunctional organic linkers and then, the Au and CaO nanoparticles are formed simultaneously in one pot via calcination. Furthermore, the as-prepared Au/CaO nanoribbons exhibit excellent catalytic performance in the transesterification reaction, which can be attributed to the small size and high distribution of CaO nanoparticles as well as the special 1D structure with high surface area. Moreover, leaching and deactivation, which are the main problems of CaO-based catalysts, are remarkably reduced due to the presence of hydrophobic Au nanoparticles on the surface of the CaO nanoribbons. Consequently, the Au/CaO nanoribbons can be used as recyclable catalysts with high activity for biodiesel production.

Autocatalytic synthesis of multifunctional precursors for fabricating silica microspheres with well-dispersed Ag and Co3O4 nanoparticles.

Herein, an autocatalytic route to fabricate dual metal ion-equipped organic/inorganic hybrid silica, an ideal precursor for multifunctional silica-based composites integrated with well-dispersed Ag and Co3O4 nanoparticles was demonstrated. Significantly, by rational selection of reactants, such dual metal ion-equipped organic/inorganic hybrid silica can be synthesized through successive spontaneous reactions under near neutral conditions without an additional catalyst. Both the Ag+ and Co2+ ions are introduced into silica by chemical bonds, which favor the formation of small-sized and well-dispersed Ag and Co3O4 nanoparticles without aggregation in the entire silica matrix. After calcination, multifunctional silica composites equipped with well-dispersed Ag and Co3O4 nanoparticles were obtained. The as-obtained silica composites, as indicated by scanning electron microscopy (SEM) and transmission electron microscopy (TEM), have a spherical morphology and smooth surface. TEM tests also reveal the well dispersed fashion of Ag and Co3O4 nanoparticles. In addition, the obtained Ag-Co3O4@SiO2 composites exhibit good catalytic performance in the reduction of methylene blue (MB) with NaBH4 as a reducing agent, and can be readily recycled by an external magnetic field due to their superparamagnetic properties.

One-step preparation of magnetic recyclable quinary graphene hydrogels with high catalytic activity.

Metal nanoparticles (NPs) displayed overwhelming superiority in catalysis towards the corresponding bulk-phase materials; nevertheless, how to further improve catalytic activity was still an ongoing subject. Herein, we have combined one-step redox reaction and following freeze-dried technology to construct the quinary reduced graphene oxide nanosheets (rGS)/Fe2O3-PdPt/polypyrrole (PPy) hydrogels. Compared with traditional catalysts, their catalytic property was improved via two ways: construction of three-dimensional (3D) rGS hydrogels instead of two-dimensional rGS and synthesis of bimetallic alloys instead of monometallic NPs. The highly dispersed PdPt with diameter as small as 3.2nm uniformly loaded on hydrogel surface. Due to special interconnected and porous structure, the reactants were easily adsorbed in hydrogels and contacted with PdPt alloys. To explain the contributions of bimetallic alloys and 3D rGS structure on enhanced catalytic activity, the catalytic property of quinary hydrogels was compared with reference samples. Besides superior activity, they also displayed good reusability, since hydrogels could be magnetically recycled owing to the existence of Fe2O3 NPs.

A simple way to prepare reduced graphene oxide nanosheets/Fe2O3-Pd/N-doped carbon nanosheets and their application in catalysis.

The catalysts with Pd and γ-Fe2O3 nanoparticles embedded between reduced graphene oxide nanosheets (rGS) and N-doped carbon nanosheets (NCS) were prepared through a two-step method. Firstly, graphene oxide nanosheets (GS)/prussian blue (PB)-Pd/polypyrrole (PPy) composites were synthesized by using pyrrole monomer as reductant, K3Fe(CN)6 and PdCl2 as oxidants in the presence of GS via a redox reaction. Subsequently, the as-obtained GS/PB-Pd/PPy composites were calcinated in N2 atmosphere. During the heat-treatment, carbonization of PPy to NCS, conversion of nonmagnetic PB to magnetic γ-Fe2O3 nanoparticles, and reduction of GS to rGS were finished, simultaneously. rGS/Fe2O3-Pd/NCS composites exhibited good catalytic activity toward reduction of 4-nitrophenol. The rate constant k and turnover frequency were calculated and compared with recent reports. Owing to γ-Fe2O3 nanoparticles, the rGS/Fe2O3-Pd/NCS composites could be quickly separated by magnet and reused without obvious decrease in activity.

A Simple Method for the Preparation of TiO2 /Ag-AgCl@Polypyrrole Composite and Its Enhanced Visible-Light Photocatalytic Activity.

A novel and facile method was developed to prepare a visible-light driven TiO2 /Ag-AgCl@polypyrrole (PPy) photocatalyst with Ag-AgCl nanoparticles supported on TiO2 nanofibers and covered by a thin PPy shell. During the synthesis, the PPy shell and Ag-AgCl nanoparticles were prepared simultaneously onto TiO2 nanofibers, which simplified the preparation procedure. In addition, because Ag-AgCl aggregates were fabricated via partly etching the Ag nanoparticles, their size was well controlled at the nanoscale, which was beneficial for improvement of the contact surface area. Compared with reference photocatalysts, the TiO2 /Ag-AgCl@PPy composite exhibited an enhanced photodegradation activity towards rhodamine B under visible-light irradiation. The superior photocatalytic property originated from synergistic effects between TiO2 nanofibers, Ag-AgCl nanoparticles and the PPy shell. Furthermore, the TiO2 /Ag-AgCl@PPy composite could be easily separated and recycled without obvious reduction in activity.

One Step Preparation of Reduced Graphene Oxide/Pd-Fe3 O4 @Polypyrrole Composites and Their Application in Catalysis.

The simple preparation of catalysts with superior catalytic activity and good reusability is highly desirable. Herein, we report a novel strategy to construct reduced graphene oxide (rGO)/Pd-Fe3 O4 @polypyrrole (PPy) catalysts with Pd and Fe3 O4 nanoparticles anchored on a rGO nanosheet surface and wrapped in a PPy shell. The synthesis and assembly of both the Pd and Fe3 O4 nanoparticles, the preparation of the PPy layer, and the reduction of graphene oxide nanosheets were finished in one step. In the system, the PPy layer not only prevented aggregation of Pd and Fe3 O4 nanoparticles, but also generated a synergistic effect with precursor Pd(2+) ions, which led to a high dispersity of as-prepared Pd nanoparticles. Although the procedure was simplified to one step, the catalytic activity and reusability were not sacrificed. In the reduction of 4-nitrophenol, their catalytic performance was better than that in recent reports. Moreover, the catalysts showed good reusability owing to their magnetic properties.

A simple way to prepare Pd/Fe3O4/polypyrrole hollow capsules and their applications in catalysis.

Preparation of catalysts with good catalytic activity and high stability, together with magnetic separation property, in a simple way is highly desirable. In this paper, we reported a novel strategy to construct magnetic recyclable hollow capsules with Pd and Fe3O4 nanoparticles embedded in polypyrrole (PPy) shell via only two steps: first, synthesization of Pd nanoparticles, preparation of Fe3O4 nanoparticles, and formation of PPy shell were finished in one-step on the surface of polystyrene (PS) nanospheres; then, the PS core was selectively removed by tetrahydrofuran. The Pd/Fe3O4/PPy hollow capsules exhibited good catalytic property in reduction of 4-nitrophenol with NaBH4 as reducing agent, and the reaction rate constants were calculated through pseudo-first-order reaction equation. Due to incorporation of Fe3O4 nanoparticles, the catalysts could be quickly separated from the reaction solution by magnet and reused without obvious catalytic loss. Besides catalytic property and reusability, their stability was also examined by HNO3 etching experiment. Compared with bare Pd and Fe3O4 nanoparticles, the stability of both Pd and Fe3O4 nanoparticles in hollow capsules was largely improved owing to the protection of PPy shell. The good catalytic performance, ease of separation, high stability and especially a simple preparation procedure, made Pd/Fe3O4/PPy hollow capsules highly promising candidates for diverse applications.

Self-catalytic synthesis of metal oxide nanoclusters@mesoporous silica composites based on successive spontaneous reactions at near neutral conditions.

A facile self-catalytic approach for the synthesis of metal oxide nanoclusters@mesoporous silica was proposed by subtly making use of successive spontaneous reactions in solution at near neutral conditions.

A simple way to prepare Au@polypyrrole/Fe3O4 hollow capsules with high stability and their application in catalytic reduction of methylene blue dye.

Metal nanoparticles are promising catalysts for dye degradation in treating wastewater despite the challenges of recycling and stability. In this study, we have introduced a simple way to prepare Au@polypyrrole (PPy)/Fe3O4 catalysts with Au nanoparticles embedded in a PPy/Fe3O4 capsule shell. The PPy/Fe3O4 capsule shell used as a support was constructed in one-step, which not only dramatically simplified the preparation process, but also easily controlled the magnetic properties of the catalysts through adjusting the dosage of FeCl2·4H2O. The component Au nanoparticles could catalyze the reduction of methylene blue dye with NaBH4 as a reducing agent and the reaction rate constant was calculated through the pseudo-first-order reaction equation. The Fe3O4 nanoparticles permitted quick recycling of the catalysts with a magnet due to their room-temperature superparamagnetic properties; therefore, the catalysts exhibited good reusability. In addition to catalytic activity and reusability, stability is also an important property for catalysts. Because both Au and Fe3O4 nanoparticles were wrapped in the PPy shell, compared with precursor polystyrene/Au composites and bare Fe3O4 nanoparticles, the stability of Au@PPy/Fe3O4 hollow capsules was greatly enhanced. Since the current method is simple and flexible to create recyclable catalysts with high stability, it would promote the practicability of metal nanoparticle catalysts in industrial polluted water treatment.

Preparation of yolk-shell Fe(x)O(y)/Pd@mesoporous SiO2 composites with high stability and their application in catalytic reduction of 4-nitrophenol.

Yolk-shell composites with a movable Fe(x)O(y) core and mesoporous SiO2 (mSiO2) shell, together with Pd nanoparticles uniformly anchoring on the inner surface, were prepared. The structure and composition of as-prepared catalysts were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, Brunauer-Emmett-Teller measurement and Fourier-transform infrared spectroscopy, respectively. They are ideal candidates as nanoreactors for heterogeneous catalysis due to their special structure. The catalytic performance of Fe(x)O(y)/Pd@mSiO2 composites was studied by the reduction of 4-nitrophenol with NaBH4 as a reducing agent. Their reaction rate constant was calculated according to the pseudo-first-order reaction equation. The catalysts could be easily recycled by an external magnetic field due to their superparamagnetic property. Besides good catalytic property, another merit of Fe(x)O(y)/Pd@mSiO2 composites was high stability. We have compared the stability between Fe(x)O(y)/Pd@mSiO2 and Fe3O4@C/Pd composites by ultrasonic treatment and HNO3 solution etching, the stability of the former was much better than the later.

Facile access to ultrasmall Eu2O3 nanoparticle-functionalized hollow silica nanospheres based on the spontaneous formation and decomposition of a cross-linked organic/inorganic hybrid core.

We report a promising strategy for the facile synthesis of ultrasmall nanoparticle-functionalized hollow silica nanospheres by using a functional cross-linked organic/inorganic hybrid core, which can be obtained simply through successive spontaneous reactions in water.

A new strategy for assembling multifunctional nanocomposites with iron oxide and amino-terminated PAMAM dendrimers.

A new strategy for assembling multifunctional nanocomposites with magnetic particles and amino dendrimers was reported. In this strategy, the amino terminated PAMAM G5.0 and Fe(3)O(4) NPs prepared by co-deposition method and further modified by aminosilane by two sol-gel processes were combined with the hydrophilic spacer of PEG dicarboxylate by amidation. The nanocomposites were characterized by means of X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), atom force microscopy (AFM), superconducting quantum interference device (SQUID) magnetometer, and hydrophilicity analysis. The results showed that the multifunctional nanocomposites were spherical with the mean diameter of 180 nm and exhibited good dispersion and hydrophilicity. The new strategy put forward here provides an effective route to functionalizing Fe(3)O(4) NPs with various amino dendrimers for drug and gene delivery as well as biological detection.