Search

Hydrogen production by electrochemical water splitting is one of the best ways to store renewable energy. Metal organic framework (MOF)-derived non-precious metal catalysts are an effective idea for large-scale commercialization and electrolysis of water for hydrogen production. Herein, we have synthesized Ni,Mo bimetallic selenide MoSe 2 @NiSe 2 heterojunctions with hollow core-shell using a selenization reaction to combine MoSe 2 with NiMOF-derived NiSe 2. The spherical clusters of MoSe 2 prevents the agglomeration and sintering of NiSe 2 and shorten the electron transfer distance form MoSe 2 to NiSe 2. The electron flow between the transition metals Ni and Mo after the selenization reaction, which alters the electronic structure of NiMOF and MoSe 2. NiSe 2 derived from NiMOF provides more active center as well as better conductivity to accelerate the electron transfer rate. Thus facilitating the HER catalytic process. Electrochemical analysis confirmed that the activity of Hydrogen evolution reaction (HER) of MoSe 2 @NiSe 2 was significantly increased in 0.5 M H 2 SO 4 , with an overpotential of 187 mV at 10 mA cm−2 and a tafel slope of 71.43 mV dec−1. This work provides a new route for the design and preparation of the NiMOF-based catalysts in HER. [Display omitted] • MoSe 2 @NiSe 2 heterojunctions with hollow core-shell was synthesized. • The HER activity of MoSe 2 @NiSe 2 was significantly increased. • The core-shell interface of MoSe 2 @NiSe 2 exhibiting sufficient active sites. • NiSe 2 and MoSe 2 synergistically accelerate the charge transfer rate. [ABSTRACT FROM AUTHOR]

In this paper, porous NiO nanoflake arrays@V 2 O 5 nanoparticles (PNFAs@VNPs) composite is fabricated on Ni foam through a facile hydrothermal process. The PNFAs@VNPs composite has an ordered array structure, a large active surface, and favorable physical stability. Based on the CV profile, the specific capacitance can achieve 950 F g−1 and remain stable at 95.8 % of the original value after 5000 loops. When the PNFAs@VNPs composite is assembled into a symmetric supercapacitor, the energy density can reach 67.0 W h kg−1 at a power density of 550 W kg−1. Even if the power density rises to 11,000 W kg−1, the energy density can still be held at 25.3 W h kg−1. The high supercapacitive property of the PNFAs@VNPs composite is owed to the synergic action of the PNFAs and VNPs. The PNFAs@VNPs composite with the advantages of battery-type and capacitive-type pseudocapacitances has higher charge transfer dynamics, making it a potential supercapacitive electrode material. [Display omitted] • Porous NiO nanoflake arrays (PNFAs) is successfully prepared on nickel foam. • V 2 O 5 nanoparticles (VNPs) are loaded on the PNFAs to form a hierarchical structure. • The PNFAs@VNPs has the advantages of Faraday and intercalation type pseudocapacitor. • The PNFAs@VNPs shows a specific capacitance of 950 F g−1at 5 mV s−1. • The PNFAs@VNPs supercapacitor has an energy density of 67.0 W h kg−1 at 550 W kg−1. [ABSTRACT FROM AUTHOR]

V 2 O 5 nanobelt arrays (VNBAs) is fabricated on Ni foam by using an easy hydrothermal route and then NiO nanosheet arrays (NNSAs) is grown on VNBAs by using a simple chemical bath deposition approach to form VNBAs/NNSAs composite. It is found that the monocrystalline VNBAs with a lamellar structure is uniformly distributed on nickel foam and the polystalline NNSAs with a close packed structure is closely covered on the VNBAs. CV, GCD, EIS and CA electrochemical techniques are used to test the supercapacitive properties of the VNBAs/NNSAs composite. The single electrode displays a high specific capacity of 875 F g−1, a good cycling stability of 96.1%, a small charge transfer resistance of 1.32 Ω and a rapid ion diffusivity of 2.5 × 10−8 cm2 s−1. The symmetric supercapacitor combined by the VNBAs/NNSAs displays a large energy density of 120.1 W h kg−1 at 400 W kg−1 and it retains 68.3 W h kg−1 at 8000 W kg−1. The VNBAs/NNSAs composite with high electrochemical performance is a potential supercapacitor electrode material. [Display omitted] • The V 2 O 5 nanobelt arrays (VNBAs) is successfully prepared on a nickel foam. • The NiO nanosheet arrays (NNSAs) is compounded on the VNBAs to form a hierarchy. • The VNBAs/NNSAs shows a high specific capacitance of 875 F g−1 at 5 mV s−1. • The VNBAs/NNSAs has an energy density of 120.1 W h kg−1 at 400 W kg−1. • The high performance of the VNBAs/NNSAs are ascribed to its synergistic effect. [ABSTRACT FROM AUTHOR]

In this work, the Bi 2 Se 3 /Mo 3 Se 4 composite is obtained through electrochemical activation of Bi 2 Se 3 /MoSe 2 composite, which has been synthesized by an ordinary hydrothermal reaction closely followed by selenization process. The Bi 2 Se 3 /Mo 3 Se 4 composite appears good electrochemical property as the negative electrode material for sodium ion batteries (the stable reversible capacity is 409 (346) mAh g−1 at 100 (1000) mA g−1). The outstanding electrochemical property can be attributed to the unique Bi 2 Se 3 /Mo 3 Se 4 composite architecture, in which Bi 2 Se 3 is responsible for offering a high capacity, and Mo 3 Se 4 is responsible for improving electrochemcial stability. Moreover, the small particle sizes for Bi 2 Se 3 /Mo 3 Se 4 resulting from the amorphous to crystalline transitions during cycling is also the cause of the increased stability of the electrode. The design of the Bi 2 Se 3 /Mo 3 Se 4 composite provides a potential tactics to construct other metal selenides composites for sodium-ion battery anode. • Bi 2 Se 3 /Mo 3 Se 4 composite was synthesized by convenient strategy. • Bi 2 Se 3 /Mo 3 Se 4 composite exhibits excellent cycling performance for SIBs anode. • Bi 2 Se 3 /Mo 3 Se 4 composite shows good rate capability for SIBs anode. [ABSTRACT FROM AUTHOR]

In this paper, four NiO nano-arrays with different morphology on nickel foam were synthesized by a hydrothermal approach. It is found that the porous single crystal NiO nanoflake array (PNFA) holds superior electrochemical properties, better than the other three samples. The specific capacitance of the PNFA obtained from the cyclic voltammetry curve was 716 F g−1 and that derived from the galvanostatic charge-discharge curve was 589 F g−1 in three-electrode system. The cycling stability of the PNFA could retain as high as 92.4% after 5000 cycles. When the PNFA was assembled into a symmetric supercapacitor, the PNFA//PNFA device exhibited an energy density of 39.3 W h kg−1 (at 550 W kg−1) and could retain 13.2 W h kg−1 (at 11,000 W kg−1) in two-electrode system. Furthermore, the SEM, XRD, TEM and XPS results prove that the PNFA is a special porous single crystal structure, which combines the advantages of the cross-linked single crystal structure for facilitating electron transfer and the porous structure providing more interfaces for insertion/exit of electrolyte ions from the active material. It indicates that the PNFA is a potential electrode material for supercapacitors. [Display omitted] • Porous single crystal NiO nanoflake array (PNFA) is directly grown on nickel foam. • The PNFA is prepared by a facile hydrothermal method following an annealing process. • The PNFA combines the advantages of porous material and single crystal material. • The PNFA shows a specific capacitance of 716 F g−1 at a scan rate of 5 mV/s. • The PNFA//PNFA supercapacitor has an energy density of 39.3 W h kg−1 at 550 W kg−1. [ABSTRACT FROM AUTHOR]

• The effects of Sc, Y and Zr on the performances and microstructure evolution of Al-0.7Mg-0.6Si-0.2Ce alloys were studied. • An excellent combination of strength, elongation and electrical conductivity was achieved with the addition of Sc and Y. • The strengthening and electrical resistance mechanism of the studied alloys were revealed by statistical calculation. [Display omitted] In order to achieve the compatibility between excellent mechanical properties and good electrical conductivity of Al-Mg-Si alloys, detailed investigation was carried out to understand the microstructure evolution and their influences on performances of different Al-0.7Mg-0.6Si-0.2Ce-X (X Sc, Y and Zr) alloys prepared by casting, homogenization, hot extrusion, solution and aging treatments. Under aging state, Ce can form a large number of micron-sized AlCeSi and a few AlCeFeSi phase. The strength increased to 334 MPa as a result of decreased grain size and improved precipitation effect and the electrical conductivity increased up to 53.53%IACS because of lower solute Si atoms. The β" precipitates were coarsened and consequently the volume fracture was largely reduced due to the presence of Sc element, leading to the decreased strength of 311 MPa. The more solute Mg, Si and Sc atoms increased the degree of free electron scattering and the electrical conductivity decreased to 51.86%IACS. It is also found that Sc significantly enhanced the elongation of the alloy from 11.8% to 18.0%, which might be attributed to the formation of Al 3 Sc and (Al, Si) 3 Sc phases. The addition of Y raised the electrical conductivity of Al-Mg-Si-Ce alloy to 55.79%IACS by ameliorating the volume fraction and distribution of β" precipitates and decreasing the solute Si atoms. The co-addition of Sc and Y inherited the advantages of such two alloys. The ultimate tensile strength, elongation, electrical conductivity of Al-0.7Mg-0.6Si-0.2Ce-0.2Sc-0.1Y alloy processed by aging treatments is 336 MPa, 19.4% and 53.11%IACS, respectively. [ABSTRACT FROM AUTHOR]