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Developing a high-efficienct, low-cost and stable non-noble-metal-based bifunctional electrocatalyst for the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) as oxygen electrode material in the rechargeable zinc–air battery is crucial in renewable energy conversion technologies. In this work, nitrogen-doped hollow carbon sphere (NHCS) decorated with various nickel selenide (NixSe) nanoparticles had been designed and successfully prepared. Among them, the Ni0.85Se–NHCS with the highest percentage of Ni3+ could serve as a new efficient bifunctional electrocatalyst toward ORR/OER (with an onset potential of 0.850 V for ORR and a potential of 1.583 V at 10 mA·cm−2 for OER) in an alkaline medium. Furthermore, the assembled Zn–air battery coupled with Ni0.85Se–NHCS electrode has excellent discharging–charging performance and long lifetime. This work provides a valuable understanding on transition metal non-oxide electrocatalysts and expands the applications of selenide-based materials.

The nanofluid as a pivotal role in heat transfer system has attracted more and more attention. Herein, the stearic acid-modified CuS (SA-CuS) nanoparticles with a uniform diameter of 60 nm were synthesized successfully by a facile two-phase approach. Accordingly, the CuS-oil nanofluids, with SA-CuS concentrations ranging from 0.01 to 0.04 vol%, were prepared by a one-step method in the heat transfer oil. These CuS-oil nanofluids exhibit good stability and considerable enhanced thermal conductivity. The improvement is even up to 20.5% with a volume fraction of 0.04 vol% at 30 °C. Furthermore, the effect of volume fraction and temperature on the viscosity of the nanofluids was also systematically investigated.

Seven 3-D metallic complexes coordinated and controlled by the deprotonated anions of H2BTA ligand (H2BTA = bis(tetrazolyl)amine): a 0-D compound of Co(HBTA)3·4.5H2O (1), two 1-D compounds of Cu(BTA)(H2O)2 (2) and Mn4(BTA)4(H2O)12·2H2O (3), a 2-D compounds [Mn7(BTA)6(OH)2(H2O)12] (4) and three 3-D compounds containing two isomorphous complexes of [Mn(BTA)2Na2(H2O)2] (5) and [Co(BTA)2Na2(H2O)2] (6) as well as Mn(BTA)(H2O) (7) have been synthesized under different synthetic conditions and characterized by single crystal X-ray diffraction analysis. In 1–7, the deprotonated anions of the H2BTA ligand control the different crystal structures using not only the different coordinations to transition metal ions as several different multidentate ligands but simultaneously the formation of complementary intermolecular hydrogen bonds.

The centrosymmetric title complex, [Fe(C2H2N9)2(H2O)2]·2H2O, has been prepared by an in situ [2+3] cyclo­addition reaction of dicyanamide with sodium azide and ferrous sulfate, with heating and stirring. The FeII ion is coordinated by four N atoms from two 5-(1H-tetra­zol-5-ylamino)-1H-tetra­zolate ligands and two water mol­ecules in axial positions in an octa­hedral geometry. The complex is linked into a three-dimensional network by O—H⋯N, N—H⋯O and N—H⋯N hydrogen bonds.