Biochar-Mediated Zirconium Ferrite Nanocomposites for Tartrazine Dye Removal from Textile Wastewater.

To meet the current challenges concerning the removal of dyes from wastewater, an environmentally friendly and efficient treatment technology is urgently needed. The recalcitrant, noxious, carcinogenic and mutagenic compound dyes are a threat to ecology and its removal from textile wastewater is challenge in the current world. Herein, biochar-mediated zirconium ferrite nanocomposites (BC-ZrFe2O5 NCs) were fabricated with wheat straw-derived biochar and applied for the adsorptive elimination of Tartrazine dye from textile wastewater. The optical and structural properties of synthesized BC-ZrFe2O5 NCs were characterized via UV/Vis spectroscopy, Fourier transform Infra-red (FTIR), X-Ray diffraction (XRD), Energy dispersive R-Ray (EDX) and Scanning electron microscopy (SEM). The batch modes experiments were executed to explore sorption capacity of BC-ZrFe2O5 NCs at varying operative conditions, i.e., pH, temperature, contact time, initial dye concentrations and adsorbent dose. BC-ZrFe2O5 NCs exhibited the highest sorption efficiency among all adsorbents (wheat straw biomass (WSBM), wheat straw biochar (WSBC) and BC-ZrFe2O5 NCs), having an adsorption capacity of (mg g-1) 53.64 ± 0.23, 79.49 ± 0.21 and 89.22 ± 0.31, respectively, for Tartrazine dye at optimum conditions of environmental variables: pH 2, dose rate 0.05 g, temperature 303 K, time of contact 360 min and concentration 100 mg L-1. For the optimization of process variables, response surface methodology (RSM) was employed. In order to study the kinetics and the mechanism of the adsorption process, kinetic and equilibrium mathematical models were used, and results revealed 2nd order kinetics and a multilayer chemisorption mechanism due to complexation of hydroxyl, Fe and Zr with dyes functional groups. The nanocomposites were also recovered in five cycles without significant loss (89 to 63%) in adsorption efficacy. This research work provides insight into the fabrication of nanoadsorbents for the efficient adsorption of Tartrazine dye, which can also be employed for practical engineering applications on an industrial scale as efficient and cost effective materials.

Ultrathin Pd-based nanosheets: syntheses, properties and applications.

Two-dimensional (2D) noble metal-based nanosheets (NSs) have received considerable interest in recent years due to their unique properties and widespread applications. Pd-based NSs, as a typical member of 2D noble metal-based NSs, have been most extensively studied. In this review, we first summarize the research progress on the synthesis of Pd-based NSs, including pure Pd NSs, Pd-based alloy NSs, Pd-based core-shell NSs and Pd-based hybrid NSs. The synthetic strategy and growth mechanism are systematically discussed. Then their properties and applications in catalysis, biotherapy, gas sensing and so on are introduced in detail. Finally, the challenges and opportunities towards the rational design and controlled synthesis of Pd-based NSs are proposed.

Mixed-dimensional heterostructures of hydrophobic/hydrophilic graphene foam for tunable hydrogen evolution reaction.

The synergetic effect of hydrophilic and hydrophobic carbon can be used to obtain tunable hydrogen evolution reaction (HER) at the interface. Herein, graphene oxide (GO-Hummers method) was coated on graphene foam (GF) synthesized via chemical vapor deposition to develop mixed-dimensional heterostructure for the observation of HER. The porosity of GF not only provides an optimized diffusion coefficient for better mass transport but also modified surface chemistry (GF/GO-hydrophobic/hydrophilic interface), which results in an onset potential 50 mV and overpotential of 450 mV to achieve the current density 10 mA/cm2. The surface analysis shows that inherent functional groups at the surface played a key role in tuning the activity of hybrid, providing a pathway to introduce non-corrosive electrodes for water splitting.

Noble Metal Based Alloy Nanoframes: Syntheses and Applications in Fuel Cells.

Noble metal nanostructures are being used broadly as catalysts for energy conversion in fuel cells. To overcome the future energy crises, fuel cells are anticipated as clean energy sources because they can be operated at low temperature, their energy conversion is high and their carbon release is almost zero. However, an active and stable electrocatalyst is essential for the electrochemical reactions in fuel cells. Therefore, properties of the nanostructures greatly depend on the shape of the nanostructures. Individual as well as interaction properties are greatly affected by changes in the surface area of the nanostructures. By shape controlled synthesis, properties of the nanostructures could be further enhanced by increasing the surface area or active sites for electrocatalysts. Therefore, an efficient approach is needed for the fabrication of nanostructures to increase their efficiency, activity, or durability in fuel cells by reducing the usage of noble metals. Different types of hollow nanostructures until now have been prepared including nanoboxes, nanocages, nanoshells, nanoframes (NFs), etc. NFs are the hollow unique three-dimensional structure which have no walls-they only contain corners or edges so they have large surface area. In electrocatalytic reactions, the molecules involved in the reaction can easily reach the inner surface of the nanoframes, thus noble metals' utilization efficiency increases. NFs usually have high surface area, greater morphological and compositional stabilities, allowing them to withstand harsh environmental conditions. By considering the current challenges in fabrication of noble metal based alloy NFs as electrocatalysts, this review paper will highlight recent progress, design, and fabrication of noble metal alloy NFs through different strategies-mainly photocatalytic template, electrodeposition, Kirkendall effect, galvanic replacement, chemical/oxidative etching, combination of both and other methods. Then, electrochemical applications of NFs in fuel cells toward formic acid, methanol, ethanol, oxygen reduction reaction as well as bifunctional catalyst will also be highlighted. Finally, we will summarize different challenges in the fabrication of highly proficient nanocatalysts for the fuel cells with low cost, high efficiency and high durability, which are the major issues for the highly commercial use of fuel cells in the future.

Facile synthesis of complex shaped Pt-Cu alloy architectures.

Several intricate Pt-Cu alloy architectures have been synthesized including hexapod backbones with stretchers and caved octahedron like hexapods, as well as some other intermediates with complex structures. The mechanistic study indicates that the shape is realized via a competitive effect between etching and growth induced by different chemicals.

Noble metal alloy complex nanostructures: controllable synthesis and their electrochemical property.

Noble metal nanocrystals have been extensively utilized as promising catalysts for chemical transformations and energy conversion. One of their significant applications lies in electrode materials in fuel cells (FCs) due to their superior electrocatalytic performance towards the reactions both on anode and cathode. Nowadays, tremendous efforts have been devoted to improve the catalytic performance and minimize the usage of precious metals. Constructing multicomponent noble metal nanocrystals with complex structures provides the opportunity to reach this goal due to their highly tunable compositions and morphologies, leading to the modification of the related electrochemical properties. In this review, we first highlight the recent advances in the controllable synthesis of noble metal alloy complex nanostructures including nanoframes/nanocages, branched structures, concave/convex structures, core-shell structures and ultrathin structures. Then the effects of the well-defined nanocrystals on the modified and improved electrochemical properties are outlined. Finally, we make a conclusion with the points on the challenges and perspectives of the controllable synthesis of noble metal alloy complex nanostructures and their electrocatalytic performance.

Atomically thick Pt-Cu nanosheets: self-assembled sandwich and nanoring-like structures.

Atomically thick and flexible Pt-Cu alloy nanosheets are prepared and loaded with either Pd or Pt to produce sandwich structures or nanoring-like nanosheet structures, respectively. Core-shell alloy nanoparticles containing Rh, Ir, and Ru are also prepared. All of these structures exhibit superior specific and mass activities for the oxidation of formic acid for fuel cells for portable electronic devices as compared to commercial Pd/C catalyst.

Hierarchical Zn/Ni-MOF-2 nanosheet-assembled hollow nanocubes for multicomponent catalytic reactions.

Metal-organic frameworks (MOFs) are potentially useful molecular materials that can exhibit structure flexibilities induced by some external stimuli. Such structure transformations can furnish MOFs with improved properties. The shape-controlled growth of MOFs combined with crystal-structure transformation is rarely achieved. Herein, we demonstrate the synthesis of hierarchical Zn/Ni-MOF-2 nanosheet-assembled hollow nanocubes (NAHNs) by a facile surfactant-free solvothermal approach. The unique nanostructures undergo crystal-structure transformation from Zn/Ni-MOF-5 nanocubes to Zn/Ni-MOF-2 nanosheets, which is analogous to the dissolution and recrystallization of inorganic nanocrystals. The present synthetic strategy to fabricate isostructural MOFs with hierarchical, hollow, and bimetallic nanostructures is expected to expand the diversity and range of potential applications of MOFs.

Hierarchical MnO2/SnO2 heterostructures for a novel free-standing ternary thermite membrane.

We report the synthesis of a novel hierarchical MnO2/SnO2 heterostructures via a hydrothermal method. Secondary SnO2 nanostructure grows epitaxially on the surface of MnO2 backbones without any surfactant, which relies on the minimization of surface energy and interfacial lattice mismatch. Detailed investigations reveal that the cover density and morphology of the SnO2 nanostructure can be tailored by changing the experimental parameter. Moreover, we demonstrate a bottom-up method to produce energetic nanocomposites by assembling nanoaluminum (n-Al) and MnO2/SnO2 hierarchical nanostructures into a free-standing MnO2/SnO2/n-Al ternary thermite membrane. This assembled approach can significantly reduce diffusion distances and increase their intimacy between the components. Different thermite mixtures were investigated to evaluate the corresponding activation energies using DSC techniques. The energy performance of the ternary thermite membrane can be manipulated through different components of the MnO2/SnO2 heterostructures. Overall, our work may open a new route for new energetic materials.

One-pot fabrication of single-crystalline octahedral Pt-Cu nanoframes and their enhanced electrocatalytic activity.

Octahedral Pt-Cu nanoframes have been synthesized by a one-pot aqueous method. Due to the unique structure and possible synergetic effect of Pt and Cu components, these octahedral Pt-Cu nanoframes exhibited significantly enhanced catalytic activity toward the electro-oxidation of formic acid in comparison with commercial Pt black and Pt/C catalysts.

Fine tuning of the structure of Pt-Cu alloy nanocrystals by glycine-mediated sequential reduction kinetics.

Uniform Pt-Cu alloy nanocrystals in the shape of dendrite, yolk-cage, and box structures are prepared via a facile wet-chemical reduction route in which glycine is demonstrated to alter the reduction kinetics of metal cations, critical to the morphology of the obtained product. These alloy nanocrystals exhibit superior specific activity and stability in the electro-oxidation of methanol.

3-[(E)-(2,4-Dichloro-pbenzyl-idene)amino]-benzoic acid.

In the crystal of the title compound, C(14)H(9)Cl(2)NO(2), inversion-related dimers with R(2) (2)(8) ring motifs are formed by inter-molecular O-H⋯O hydrogen bonding. The 3-amino-benzoic acid group and the 2,4-dichlobenzaldehyde moiety subtend a dihedral angle of 55.10 (2)°. The H atom of the carboxyl group is disordered over two sites with equal occupancies.