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.

Titanium dioxide@polypyrrole core-shell nanowires for all solid-state flexible supercapacitors.

Herein, we developed a facile two-step process to synthesize TiO2@PPy core-shell nanowires (NWs) on carbon cloth and reported their improved electrochemical performance for flexible supercapacitors (SCs). The fabricated solid-state SC device based on TiO2@PPy core-shell NWs not only has excellent flexibility, but also exhibits remarkable electrochemical performance.

catena-Poly[[tetra-kis-(1H-pyrazole-κN(2))copper(II)]-µ-hexa-fluoridosilicato-κ(2)F:F'].

In the title one-dimensional coordination polymer, [Cu(SiF(6))(C(3)H(4)N(2))(4)](n), the Cu(II) atom is coordinated by two hexafluoridosilicate F atoms and four pyrazole N atoms in a distorted trans-CuF(2)N(4) octa-hedral environment. The dihedral angle between the planes of the pyrazlole rings in the asymmetric unit is 74.4 (3)°. The hexa-fluoridosilicate dianion acts as a bridging ligand, connecting the Cu(II) atoms into a [1-10] chain. The Cu and Si atoms lie on special positions with 2/m site symmetry. In the crystal, intra-chain N-H⋯F hydrogen bonds occur and weak C-H⋯F inter-actions link the chains.

catena-Poly[[[diaqua-diformatonickel(II)]-µ-1,4-bis-(1H-benzimidazol-1-yl)benzene] dihydrate].

In the title one-dimensional coordination polymer, {[Ni(CHO(2))(2)(C(20)H(14)N(4))(H(2)O)(2)]·2H(2)O}(n), the Ni(II) atom lies on a crystallographic inversion centre. It is coordinated by two formate O atoms, two water O atoms and two N atoms from two 1,4-bis-(1H-benzimidazol-1-yl)benzene (bzb) ligands, resulting in a distorted trans-NiN(2)O(4) octa-hedral coordination geometry. The bzb mol-ecule acts as a bridging ligand to connect the metal atoms into a chain propagating in [1[Formula: see text][Formula: see text]]. The dihedral angle between the benzimidazole ring and the central benzene ring in the ligand is 38.16 (9)°. In the crystal, O-H⋯O hydrogen bonds crosslink the chains into (010) sheets.

Synthesis, crystal structure, magnetic property and thermal studies of [Ni(CH(3)COO)2·(NH2CH2Ph)4].

[Ni(CH(3)COO)(2)·(NH(2)CH(2)Ph)(4)] complex was synthesized using benzylamine and nickel acetate. The molecular structure of this complex was obtained by single crystal X-ray diffraction and characterized by elemental analysis, IR spectrometry and thermal analysis. The complex crystallized in the monoclinic space group P2(1)/n with cell parameters a=11.234(4)Å, b=6.459(2)Å, c=22.647(8)Å, α=90.00, ß=91.149(4)°, γ=90.00, V=1642.8(10)Å(3), Z=2. The structure has been solved by direct methods and refined to R(1)=0.0876 for 6377 observed reflections I>2σ(I). Magnetic studies for complex show the data over the whole temperature range 5-300 K are well fitted to the Curie-Weiss law with C=1.03 cm(3) K mol(-1) and θ=-1.38 K. This fitting indicates antiferromagnetic interaction between the Ni ions and the metal center exhibits distorted octahedral coordination geometries. The thermal analysis was carried out to understand the thermal stability of the title complex.

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].