Porous nanostructured ZnCo2O4 derived from MOF-74:High-performance anode materials for lithium ion batteries

Nanostructured metal oxides derived from metal organic frameworks have been shown to be promising materials for application in high energy density lithium ion batteries. In this work, porous nanostructured ZnCo2O4and Co3O4were synthesized by a facile and cost-effective approach via the calcination of MOF-74 precursors and tested as anode materials for lithium ion batteries. Compared with Co3O4, the electrochemical properties of the obtained porous nanostructured ZnCo2O4exhibit higher specific capacity, more excellent cycling stability and better rate capability. It demonstrates a reversible capacity of 1243.2 m Ah/g after 80 cycles at 100 m A/g and an excellent rate performance with high average discharge specific capacities of 1586.8, 994.6, 759.6 and 509.2 m Ah/g at 200, 400, 600 and 800 m A/g, respectively.The satisfactory electrochemical performances suggest that this porous nanostructured ZnCo2O4is potentially promising for application as an efficient anode material for lithium ion batteries.

Micro–meso-macroporous FeCo-N-C derived from hierarchical bimetallic FeCo-ZIFs as cathode catalysts for enhanced Li-O2 batteries performance

Developing bifunctional catalysts that increase both the OER and ORR kinetics and transport reactants with high efficiency is desirable. Herein, micro–meso-macroporous FeCo-N-C-X(denoted as "MFeCo-N-C-X", X represents Fe/Co molar ratio in bimetallic zeolite imidazole frameworks FeCo-ZIFs) catalysts derived from hierarchical M-FeCo-ZIFs-X was prepared. The micropores in M-FeCo-N-C-X have strong capability in O2 capture as well as dictate the nucleation and early-stage deposition of Li2O2,the mesopores provided a channel for the electrolyte wetting, and the macroporous structure promoted more available active sites when used as cathode for Li-O2 batteries. More importantly, M-Fe CoN-C-0.2 based cathode showed a high initial capacity(18,750 mAh g-1@0.1 A g-1), good rate capability(7900 m Ah g-1@0.5 A g-1), and cycle stability up to 192 cycles. Interestingly, the FeCo-N-C-0.2 without macropores suffered relatively poorer stability with only 75 cycles, although its discharge capacity was still as high as 17,200 mA h g-1(@0.1 A g-1). The excellent performance attributed to the synergistic contribution of homogeneous Fe, Co nanoparticles and N co-doping carbon frameworks with special micro–meso-macroporous structure. The results showed that hierarchical FeCo-N-C architectures are promising cathode catalysts for Li-O2 batteries.

Preparation and application of ZnO doped Pt-CeO2 nanofibers as electrocatalyst for methanol electro-oxidation

ZnO doped Pt/CeO2 nanocomposites were prepared by electrospinning and reduction impregnation.Xray diffraction（XRD）,transmission electron microscopy（TEM）,energy disperse spectroscopy（EDS） and X-ray photoelectron spectroscopy（XPS） were employed to characterize the nanocomposites.It is observed that ZnO and CeO2 form the hexagonal wurtzite phase and cubic fluorite phase in the nanocomposite,respectively,whilst Pt nanoparticles（NPs） with the number-averaged size of ca.3.1 nm are uniformly distributed on the surface of nanofibers.The mass fraction of Pt NPs in the nanocomposites is about 10 wt%.The doping of ZnO is effective to promote reactive oxygen species,surface reaction sites and the interaction between Pt and oxides.The catalytic performance of nanocomposites was evaluated by the methanol electro-oxidation.indexed with the catalytic activity,stability of catalyst.As a result,it is found that the nanocomposite exhibits much higher activity and stability for methanol oxidation than the undoped Pt/CeO2 catalyst.

Rod-shaped thiocyanate-induced abnormal band gap broadening in SCN^- doped CsPbBr3 perovskite nanocrystals

In this work, the pseudohalide thiocyanate has been demonstrated as a promising alternative to the halide anion to engineer optoelectronic properties of inorganic/ organic hybrid perovskites because it exhibits better chemical stability than the halide anion. Previous reports have suggested that the ionic radii and electronegativity of SCN- is close to that of I^-; the SCN^- doped CH3NH3PbI3 exhibited similar optical properties as pure CH3NH3PbI3. Consequently, it was expected that doping of CsPbBr3 perovskite with SCN^- would result in band gap narrowing. Interestingly, the photoluminescent all-inorganic CsPbBr3 perovskite nanocrystals exhibit an abnormal blue shift in optical properties and improvement of the crystallinity when successfully doped by SCN^-. Combined experimental and theoretical investigations revealed that doping of the CsPbBr3 perovskite with the rod-like SCN^- anion introduced disorder in the crystal lattice, leading to its expansion, and impacted the electronic structure of the perovskite with band gap broadening.

Near UV luminescent Cs_(2)NaBi_(0.75)Sb_(0.25)Cl_(6)perovskite colloidal nanocrystals with high stability

Near UV highly luminescent colloidal Cs_(2)NaBiCl_(6)nanocrystals(NCs)were synthesized by a simple low-cost ligand-assisted reprecipitation method.In our strategy,metal chloride precursors were added to the mixture of anti-solvent and ligand at room-temperature.The obtained Cs_(2)NaBiCl_(6)NCs exhibited a bright blue emission with significantly improved photoluminescence quantum yield(PLQY)of 39.05%.The optical properties and stability were greatly enhanced by doping Sb where Cs_(2)NaBi_(0.75)Sb_(0.25)Cl_(6)showed a high PLQY of 46.57%,and both the powder and the colloidal solution exhibited superior stability.