Exploiting a High-Performance "Double-Carbon" Structure Co9S8/GN Bifunctional Catalysts for Rechargeable Zn-Air Batteries.

Rational synthesis of bifunctional electrocatalysts with high performance and strong durability is highly demanded rechargeable metal-air battery. In this work, ZIF-derived Co9S8/C coated with conductive graphene nanosheet (Co9S8/GN) was synthesized by a simple solvothermal method and formed a stable double-carbon structure. As expected, the prepared Co9S8/GN catalyst exhibits a high catalytic activity (ΔE: 0.88 V) and long-term durability toward both oxygen reduction reaction and oxygen evolution reaction (ORR and OER), which is even superior to the Pt/C + Ir/C mixture (0.91 V). In addition, the Zn-air battery with the Co9S8/GN catalyst showed higher power density (186 mW cm-2) and more stable charge-discharge cycling performances (2000 cycles) than the Pt/C + Ir/C (118 mW cm-2). Based on these analysis results, the favorable catalytic performance of ORR/OER should be illustrated by the following reasons: (i) large specific surface area and unique mesoporous structure, providing abundant active sites; (ii) good conductivity, accelerating the electrons transfer; and (iii) the unique stable "double-carbon" structures (metal-S-C-C), preventing the agglomeration of metal sulfide, building new quick transfer pathway, and forming the strong electron coupling ability and synergistic effect.

Controllable Hortensia-like MnO2 Synergized with Carbon Nanotubes as an Efficient Electrocatalyst for Long-Term Metal-Air Batteries.

The exploitation of a high-activity and low-cost bifunctional catalyst for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) as the cathode catalyst is a research priority in metal-air batteries. Herein, a novel bifunctional hybrid catalyst of hortensia-like MnO2 synergized with carbon nanotubes (CNTs) (MnO2/CNTs) is controllably synthesized by reasonably designing the crystal structure and morphology as well as electronic arrangement. On the basis of these strategies, the hybrid accelerates the reaction kinetics and avoids the change of structures. As expected, MnO2/CNTs exhibit a remarkable ORR and OER activity [low ORR Tafel slope: 71 mV dec-1, low OER Tafel slope: 67 mV dec-1, and small potential difference (Δ E): 0.85 V] and a long-term stability, which should be attributed to its unique morphology, K+ ions in the 2 × 2 tunnels, and synergistic effect between MnO2 and CNTs. Notably, in zinc-air batteries (ZABs), aluminum-air batteries (AABs), and magnesium-air batteries (MABs), the composite shows high power density (ZABs: 243 mW cm-2, AABs: 530 mW cm-2, and MABs: 614 mW cm-2) and large specific capacities (793 mA h gZn-1, 918 mA h gAl-1, and 878 mA h gMg-1). Importantly, the rechargeable ZABs reveal small charge-discharge voltage drop (0.81 V) and strong cycle durability (500 h), which are better than the noble-metal Pt/C + IrO2 mixture catalyst (the voltage drop: 1.15 V at first and 2 V after 100 h). These superior performances together with the simple synthetic method of the hybrid reveal great promise in large-power energy storage and conversion equipment.

Alkaline Exchange Polymer Membrane Electrolyte for High Performance of All-Solid-State Electrochemical Devices.

As a potential solution to ubiquitous energy concerns, anion-exchange membranes (AEMs) have been widely used as the electrolyte in alkaline fuel cells (AFCs), and significant refinement of AEMs has been achieved in the past few decades. However, it remains unknown whether AEMs can be used as an electrolyte in a solid-state supercapacitor or zinc-air battery. A low-cost alkaline exchange membrane electrolyte composed of chitosan and poly(diallyldimethylammonium chloride) that possesses a high OH- conductivity (0.024 S cm-1), strong alkaline stability (216 h at 8 M KOH), good thermal stability, and low degree of anisotropic swelling, was found to provide a high electrochemical performance in all-solid-state devices. Prototypes of the solid AFC with the membrane shows superior stability over 500 h. The carbon nanotube-based all-solid-state supercapacitor with the membrane generated a rectangular cyclic voltammetry curve up to 10 V s-1 and excellent cycling stability of 4000 cycles with 84% specific capacitance retention. The all-solid-state zinc-air battery demonstrates high power density (48.9 mW cm-2). These advantages indicate that the membrane is a promising electrolyte for all-solid-state electrochemical devices.

A sensitive impedimetric DNA biosensor for the determination of the HIV gene based on graphene-Nafion composite film.

An impedimetric HIV-1 gene biosensor has been developed based on graphene-Nafion composite film. The biosensor was fabricated by adsorbing the single-stranded DNA (ssDNA) on graphene-Nafion modified on the surface of glassy carbon electrode via the π-π* stacking interactions. As the negative ssDNA and the steric hindrance, the electron transfer resistance of the electrodes toward the [Fe(CN)6]3-/4 redox couple was difficult, the electron transfer resistance value increased. In the measurement of HIV gene, ssDNA probe with the target DNA to form double-stranded DNA (dsDNA), the formation of helix induced dsDNA to release from the surface of the biosensor. The decrease in the electron transfer resistance was in logarithmically direct proportion to the concentration of HIV-1 gene over a range from 1.0×10-13 to 1.0×10-10M. The detection limit of this sensor was 2.3×10-14M. It was found that Nafion could not only stabilize graphene but also increase the dispersion of graphene. The results demonstrate that this graphene-Nafion biosensor possesses good selectivity, acceptable stability and reproducibility for HIV-1 gene detection.

An environmentally friendly method for the fabrication of reduced graphene oxide foam with a super oil absorption capacity.

Three kinds of graphene oxide (GO) foams were fabricated using different freezing methods (unidirectional freezing drying (UDF), non-directional freezing drying, and air freezing drying), and the corresponding reduced graphene oxide (RGO) foams were prepared by their thermal reduction of those GO foams. These RGO foams were characterized by Fourier transform infrared spectroscopy, thermal gravimetric analysis, X-ray diffraction, X-ray photoelectron spectroscopy, and scanning electron microscopy. The absorption process and the factors that influence the absorption capacity were investigated. The RGO foams are hydrophobic and showed extremely high absorbing abilities for organic liquids. The absorption capacity of the RGO foams made by UDF was higher than 100 g g(-1) for all the oils tested (gasoline, diesel oil, pump oil, lubricating oil and olive oil) and had the highest value of about 122 g g(-1) for olive oil. The oil absorption capacity of the GO foams was lower than that of the RGO foams, but for olive oil, the absorption capacity was still high than 70 g g(-1), which is higher than that of most oil absorbents.

catena-Poly[[dichloridocobalt(II)]-µ-4,4'-bis-(benzimidazol-1-yl)biphen-yl].

In the title compound, [CoCl(2)(C(26)H(18)N(4))](n), the Co(II) atom (site symmetry 2) is tetra-hedrally coordinated by two chloride ions and two N atoms from 4,4'-bis-(benzimidazol-1-yl)biphenyl ligands: the complete ligand is generated by crystallographic twofold symmetry. The dihedral angle between the benzene rings is 34.67 (8)° and the angle between the benene ring and the adjacent benzimidazole ring system is 43.26 (10)°. The bridging ligand links the Co(II) atoms into chains propagating in [[Formula: see text]01].

catena-Poly[[dichloridoiron(II)]-µ-4,4''-bis-(benzimidazol-1-yl)-1,1':4',1''-terphen-yl].

In the title coordination polymer, [FeCl(2)(C(32)H(22)N(4))](n), the Fe(II) atom lies on a crystallographic twofold axis and a distorted FeCl(2)N(2) tetra-hedral coordination geometry arises. The complete ligand is generated by crystallographic twofold symmetry, resulting in an infinite one-dimensional architecture along [101].