MOFs encapsulated nanorods derived CoNi@CN composites with open structure as highly efficient bifunctional catalysts for rechargeable Zn-air batteries.

Constructing highly efficient cathode catalysts is of significance for the practical application of Zn-air batteries, while the accessibility of electrons and electrolyte to catalytic active sites is essential for the electrocatalytic processes of Zn-air battery. Herein, we established a novel strategy to construct CoNi@CN composites with open structure through template-modulating thermal transformation of Co-NRs@Co-Ni-MOF. The internal elongated Co-NRs will convert into carbon nanotubes to create an open channel to the metal active sites needed for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) processes, thereby increasing the O-containing intermediates transmission and boosting the ORR/OER performances. Surprisingly, the optimal Co3Ni1@CN-900 composites deliver excellent ORR/OER activities, affording a high half-wave potential (E1/2) of 0.869 V for ORR and a low overpotential of 366 mV for OER, as well as a narrow potential gap between ORR and OER of 0.727 V. Most impressively, the optimal Co3Ni1@CN-900 based aqueous and solid-state Zn-air batteries achieve outstanding battery properties with high OCVs, enhanced peak power densities and specific capacities, and excellent long-term charge-discharge stabilities. Meanwhile, the Co3Ni1@CN-900 based ZAB also exhibits an impressive practicality.

Metal-organic frameworks/ hydrotalcite/graphene oxide sandwich composites derived Fe-Ce@GSL hierarchical materials as highly efficient catalysts for rechargeable Zn-air batteries.

The fabrication of efficient bi-functional catalysts for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) applied in energy storage and conversion devices like Zn-air batteries to solve the growing energy and environmental crises has attracted great attentions. In this work, the Fe-Ce@GSL catalysts have developed by first constructing the MOF/LDH/GO templates with multi-stage mixed growth method followed by calcining the template at high temperature. Fe-Ni-LDH (hydrotalcite) plays the role of linking the metal organic frameworks (Fe-Ce-MOF) and graphene oxides (GO), avoiding the separation of MOFs derivatives and GO sheets during pyrolysis process. Rare-earth metal oxide (CeO2) featuring with abundant oxygen vacancies dispersed on the surface of transition-metal oxide can efficiently improve the stability of catalysts. The optimal Fe7-Ce1@GSL-800 catalysts exhibit excellent ORR/OER performances with the potential gap between ORR (E1/2 = 0.87 V) and OER (EJ=10 = 1.59 V) of 0.720 V. The aqueous Zn-air battery assembled with Fe7-Ce1@GSL-800 catalysts exhibits outstanding performances with high open circuit voltage (1.56 V), large specific capacity (801.1 mAh/g@10 mA.cm-2), and good charge-discharge cycle performances (>500 h). The Fe7-Ce1@GSL-800 based solid-state Zn-air battery also delivers an excellent performance with high specific capacity (791.7 mAh/g@5 mA.cm-2) and long cycle stability (>230 h).

One-step synthesis of amorphous nickel iron phosphide hierarchical nanostructures for water electrolysis with superb stability at high current density.

The development of noble-metal-free high-performance bifunctional catalysts for both the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) is essential but challenging for hydrogen production from water electrolysis. Herein, amorphous bimetallic nickel-iron phosphide hierarchical nanostructures enrooted on nickel-iron alloy foam (NiFeP/NFF) are facilely fabricated via direct phosphidation of NFF at low temperature and developed as an efficient self-supporting bifunctional electrocatalyst to catalyze both the OER and HER with high activity, fast kinetics and excellent stability. Moreover, an alkaline water electrolyzer simultaneously utilizing NiFeP/NFF as the cathode and anode only needs a cell voltage of 1.58 V to afford a current density of 10 mA cm-2, overpassing most of the reported bifunctional electrocatalysts and comparable to noble metal-based ones. Impressively, the NiFeP/NFF-based symmetric electrolyzer can work well without appreciable performance degradation at a high current density of 500 mA cm-2 for over 1000 h for continuous hydrogen production with 100% faradaic efficiency, showing superb durability and great promise for industrial application.

Cobalt sulfide/N,S codoped porous carbon core-shell nanocomposites as superior bifunctional electrocatalysts for oxygen reduction and evolution reactions.

Exploring highly-efficient and low-cost bifunctional electrocatalysts for both oxygen reduction reaction (ORR) and oxygen evolution reactions (OER) in the renewable energy area has gained momentum but still remains a significant challenge. Here we present a simple but efficient method that utilizes ZIF-67 as the precursor and template for the one-step generation of homogeneous dispersed cobalt sulfide/N,S-codoped porous carbon nanocomposites as high-performance electrocatalysts. Due to the favourable molecular-like structural features and uniform dispersed active sites in the precursor, the resulting nanocomposites, possessing a unique core-shell structure, high porosity, homogeneous dispersion of active components together with N and S-doping effects, not only show excellent electrocatalytic activity towards ORR with the high onset potential (around -0.04 V vs.-0.02 V for the benchmark Pt/C catalyst) and four-electron pathway and OER with a small overpotential of 0.47 V for 10 mA cm(-2) current density, but also exhibit superior stability (92%) to the commercial Pt/C catalyst (74%) in ORR and promising OER stability (80%) with good methanol tolerance. Our findings suggest that the transition metal sulfide-porous carbon nanocomposites derived from the one-step simultaneous sulfurization and carbonization of zeolitic imidazolate frameworks are excellent alternative bifunctional electrocatalysts towards ORR and OER in the next generation of energy storage and conversion technologies.

Synthesis of α-Fe2O3 nanofibers for applications in removal and recovery of Cr(VI) from wastewater.

PURPOSE: Nanomaterials such as iron oxides and ferrites have been intensively investigated for water treatment and environmental remediation applications. The purpose of this work is to synthesize α-Fe(2)O(3) nanofibers for potential applications in removal and recovery of noxious Cr(VI) from wastewater. METHODS: α-Fe(2)O(3) nanofibers were synthesized via a simple hydrothermal route followed by calcination. The crystallographic structure and the morphology of the as-prepared α-Fe(2)O(3) nanofibers were characterized by X-ray diffraction, scanning electron microscope, and transmission electron microscope. Batch adsorption experiments were conducted, and Fourier transform infrared spectra were recorded before and after adsorption to investigate the Cr(VI) removal performance and adsorption mechanism. Langmuir and Freundlich modes were employed to analyze the adsorption behavior of Cr(VI) on the α-Fe(2)O(3) nanofibers. RESULTS: Very thin and porous α-Fe(2)O(3) nanofibers have been successfully synthesized for investigation of Cr(VI) removal capability from synthetic wastewater. Batch experiments revealed that the as-prepared α-Fe(2)O(3) nanofibers exhibited excellent Cr(VI) removal performance with a maximum adsorption capacity of 16.17 mg g(-1). Furthermore, the adsorption capacity almost kept unchanged after recycling and reusing. The Cr(VI) adsorption process was found to follow the pseudo-second-order kinetics model, and the corresponding thermodynamic parameters ΔG°, ΔH°, and ΔS° at 298 K were calculated to be -26.60 kJ mol(-1), -3.32 kJ mol(-1), and 78.12 J mol(-1) K(-1), respectively. CONCLUSIONS: The as-prepared α-Fe(2)O(3) nanofibers can be utilized as efficient low-cost nano-absorbents for removal and recovery of Cr(VI) from wastewater.

Facile synthesis of ZnO nanorod arrays and hierarchical nanostructures for photocatalysis and gas sensor applications.

A facile one-step hydrothermal route was demonstrated to grow ZnO nanorod arrays and hierarchical nanostructures on arbitrary substrates without any catalysts and seeds coated before the reaction, which are prerequisite in the current two-step protocol. Meanwhile, ZnO nanoflowers composed of nanorods were obtained at the bottom of the autoclaves in the absence of substrates. An in situ spontaneous-seeds-assisted growth mechanism was tentatively proposed on the basis of the experimental data to explain the growth process of ZnO nanostructures. Moreover, the obtained ZnO nanorod arrays exhibited superior photocatalytic activity for decomposing methyl orange, and the nanoflowers showed better gas sensing performance towards some flammable gases and corrosive vapors with high sensitivity, rapid response-recovery characteristics, good selectivity and long-term stability.

Room-temperature solution synthesis of Bi2O3 nanowires for gas sensing application.

A simple room-temperature solution chemical route for bulk synthesis of high quality alpha-Bi(2)O(3) nanowires has been demonstrated. The nanowires have a diameter of about 50 nm and a length in the range of several to tens of micrometers. It was found that oleic acid played an important role in directing the growth of alpha- Bi(2)O(3) nanowires along the [102] direction, and the diameter of the nanowires increased with an increase of the reaction temperature. Furthermore, the Bi(2)O(3) nanowire sensors are highly sensitive to ppm-levels of NO(2) in ambient air with fast response, good selectivity and stability, indicating their potential applications for environmental monitoring and pollution control.

Flutelike porous hematite nanorods and branched nanostructures: synthesis, characterisation and application for gas-sensing.

Flute-like porous alpha-Fe2O3 nanorods and branched nanostructures such as pentapods and hexapods were prepared through dehydration and recrystallisation of hydrothermally synthesised beta-FeOOH precursor. Transmission electron microscopy (TEM), high-resolution TEM and selected area electron diffraction analyses reveal that the nanorods, which grow along the [110] direction, have nearly hollow cavities and porous walls with a pore size of 20-50 nm. The hexapods have six symmetric arms with a diameter of 60-80 nm and length of 400-900 nm. The growth direction of the arms in the hexapod-like nanostructure is also along the [110] direction, and there is a dihedral angle of 69.5 degrees between adjacent arms. These unique iron oxide nanostructures offer the first opportunity to investigate their magnetic and gas sensing properties. The nanostructures exhibited unusual magnetic behaviour, with two different Morin temperatures under field-cooled and zero-field-cooled conditions, owing to their shape anisotropy and magnetocrystalline anisotropy. Furthermore, the alpha-Fe2O3 nanostructures show much better sensing performance towards ethanol than that of the previously reported polycrystalline nanotubes. In addition, the alpha-Fe2O3 nanostructure based sensor can selectively detect formaldehyde and acetic acid among other toxic, corrosive and irritant vapours at a low working temperature with rapid response, high sensitivity and good stability.

Monodisperse hematite porous nanospheres: synthesis, characterization, and applications for gas sensors.

Monodisperse α-Fe(2)O(3) porous nanospheres with uniform shape and size have been synthesized via a facile template-free route. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), and Raman spectroscopy were employed to characterize the product, showing the high quality of the as-prepared α-Fe(2)O(3) porous nanospheres. Furthermore, the α-Fe(2)O(3) porous nanospheres can selectively detect ethanol, formaldehyde and acetic acid, with a rapid response and high sensitivity, from a series of flammable and toxic/corrosive gases, indicating their potential applications for high sensitivity gas sensors.

Shape-controlled synthesis of ternary chalcogenide ZnIn2S4 and CuIn(S,Se)2 nano-/microstructures via facile solution route.

We demonstrated in this paper the shape-controlled synthesis of ZnIn2S4, CuInS2, and CuInSe2 nano- and microstructures through a facile solution-based route. One-dimensional ZnIn2S4 nanotubes and nanoribbons were synthesized by a solvothermal method with pyridine as the solvent, while ZnIn2S4 solid or hollow microspheres were hydrothermally prepared in the presence of a surfactant such as cetyltrimethylammonium bromide (CTAB) or poly(ethylene glycol) (PEG). The mechanisms related to the phase formation and morphology control of ZnIn2S4 are proposed and discussed. The UV-vis absorption spectra show that the as-prepared nano- and micromaterials have strong absorption in a wide range from UV to visible light and that their band gaps are somewhat relevant to the size and morphology. The photoluminescence measurements of the ZnIn2S4 microspheres at room temperature reveal intense excitation at approximately 575 nm and red emission at approximately 784 nm. Furthermore, CuInS2 and CuInSe2 with different morphologies such as spheres, platelets, rods, and fishbone-like shapes were also obtained by similar hydrothermal and solvothermal synthesis.

TiS2 nanotubes as the cathode materials of Mg-ion batteries.

Titanium disulfide (TiS2) nanotubes were used as the cathode materials of rechargeable magnesium-ion batteries, showing potential low-cost, high-capacity, and good-reversibility properties.