Nitrogen-doped graphene quantum dots embedding CuCo-LDH hierarchical hollow structure for boosted charge storage capability in supercapacitor.

The nanostructure optimization of layered double hydroxide (LDH) can effectively alleviate fragile agglomerated problems. Herein, nitrogen-doped graphene quantum dots (NGQDs) embedded in CuCo-LDH hierarchical hollow structure is synthesized by hydrothermal and impregnation methods. The electrochemical results show that the ordered multi-component structure could effectively inhibit the aggregation and layer stacking. At the same time, the hierarchical structure establishes new electron and ion transfer channels, greatly reducing the resistance of interlayer transport and accelerating the diffusion rate of electrolyte ions. Besides, NGQDs have both good electrical conductivity and abundant active sites, which can further improve the electron transmission rate and effectively strengthen the energy storage capacity of the material. Therefore, the large specific capacity of 1009 F g-1 can be displayed at 1 A g-1. The energy density of the assembled carbon cloth (CC)@CuCo-LDH/NGQDs//activated carbon (AC) device can reach 58.6 Wh kg-1 at 850 W kg-1. Above test results indicate that CC@CuCo-LDH/NGQDs//AC devices exhibit stable multi-component hierarchical structure and excellent electrical conductivity, which provides an effective strategy for enhancing the electrochemical characteristics of asymmetric supercapacitors.

Effect of Ni on Microstructure and Mechanical Property of a Co-Ti-V-Based Superalloy.

The effect of Ni on microstructure, elemental partition behavior, γ' phase solvus temperature, lattice misfit between γ and γ' phases, and mechanical properties of the Co-8Ti-11V-xNi alloys was investigated. The result shows that the lattice misfit in the alloys decreases from 0.74% to 0.61% as the Ni content increases from 0 to 10%, and the average sizes of the cuboidal γ' phase were measured to be 312.10 nm, 112.86 nm, and 141.84 nm for the Co-8Ti-11V, Co-8Ti-11V-5Ni, and Co-8Ti-11V-10Ni, respectively. Ti, V, and Ni exhibit a slight tendency to partition into the γ' phase, while Co shows a slight tendency to partition into the γ phase. The solvus temperatures of the γ' phase were measured to be 1167°C, 1114°C, and 1108°C for the Co-8Ti-11V, Co-8Ti-11V-5Ni, and Co-8Ti-11V-10Ni alloys, respectively, by using differential scanning calorimetry (DSC). Moreover, the yield strength and ultimate strength of the Co-8Ti-11V, Co-8Ti-11V-5Ni, and Co-8Ti-11V-10Ni alloys were investigated, and the yield strength and ultimate strength of the 10Ni alloy were highest, at 219 MPa and 240 MPa. After compression at 1000°C, the dislocations cannot effectively shear the γ' phase in the 0Ni and 10Ni alloys, resulting in a relatively high compressive strength of the 0Ni and 10Ni alloys. However, the γ' phase of the 5Ni alloy is no longer visible, and its strength is the lowest.

Iodine ion doped bromo bismuth oxide modified bismuth germanate: A direct Z-scheme photocatalyst with enhanced visible-light photocatalytic performance.

A series of Z-scheme I-BiOBr/Bi12GeO20 heterostructures were successfully obtained by a simple method. The Z-scheme I-BiOBr/Bi12GeO20 heterostructures show outstanding photocatalytic performance for degrading the various organic pollutants of the waste water. For degradation of Tetracycline (TC), the Z-scheme 30I-BiOBr/Bi12GeO20 heterostructure exhibits the superior rate constant, which is about 7.73 times, 3.52 times and 1.66 times higher than that of the pure Bi12GeO20, BiOBr and I-BiOBr, respectively. Meanwhile, as we expected, the Z-scheme 30I-BiOBr/Bi12GeO20 heterostructure also displays the enhanced photocatalytic perfomance for degradation of Ciprofloxacin (CIP), 2-Mercaptobenzothiazole (MBT) and reduction of aqueous Cr(VI). The enhancement of photocatalytic performance is attributed to the high redox capacity and the strong interfacial interaction between I-BiOBr and Bi12GeO20, which can effectively improve the separation of photo-induced electron-hole pairs. Additionally, the photocatalytic mechanism over the Z-scheme I-BiOBr/Bi12GeO20 heterostructure is provided. The research work may provide a promising approach to fabricate other Z-scheme heterostructures with efficient photocatalytic performance.

Precursor-reforming strategy induced g-C3N4 microtubes with spatial anisotropic charge separation established by conquering hydrogen bond for enhanced photocatalytic H2-production performance.

Precursor-reforming strategy induced graphitic carbon nitride (g-C3N4) with different morphologies for enhanced photocatalytic hydrogen (H2) evolution activity is highly desirable. Herein, g-C3N4 microtubes (mg-C3N4) with adjustable closure degree of microtube orifice and spatial anisotropic charge separation are established by conquering hydrogen bond during thermally exfoliate precursor. Compared to the bulk g-C3N4 (bg-C3N4) and ultrathin g-C3N4 (ug-C3N4), the tubular structure endows mg-C3N4 with spatial anisotropic charge separation that accelerates transfer of charge carriers. As expected, the photocatalytic H2 evolution (PHE) activity of mg-C3N4 has been obviously enhanced. Particularly, the mg-C3N4-24 shows the best PHE activity (957.9 µmol h-1 g-1), which is over 18.72 and 3.77 times higher than the bg-C3N4 and ug-C3N4, respectively. In addition, selective photo-deposition experiment results reveal a charge carriers migration behavior that photoproduction electrons migrate to the outer shell and holes prefer to move onto the inner shell of mg-C3N4, thus achieving efficient spatial anisotropic charge separation. We firmly believe that the work presents significant advancement for the design of other materials by precursor-reforming strategy.

Yeast-derived carbon sphere as a bridge of charge carriers towards to enhanced photocatalytic activity of 2D/2D Cu2WS4/g-C3N4 heterojunction.

It is very challenging to fabricate novel, high-efficiency photocatalysts with an enhanced visible light absorption capacity, high charge carrier separation efficiency, and large specific surface area. For this purpose, a yeast-derived carbon (YC) sphere was added as a charge carrier bridge to the 2D-2D Cu2WS4/g-C3N4 heterojunction through a facile hydrothermal method. The YC sphere, as a bridge for electrons, is not only advantageous in inhibiting rapid recombination by electrons, but also remarkably enhances the visible light absorption capacity. Moreover, the YC sphere can also increase the specific surface area and surface roughness, which can enhance the adsorption of pollutant molecules and provide abundant active sites for photocatalytic reactions. The g-C3N4/YC/Cu2WS4 heterojunction showed the best photocatalytic activity for reducing hexavalent chromium Cr(VI) and decomposing tetracycline (TC) under visible light. Meanwhile, the acute toxicity of Daphnia magna (D. magna) gradually decreases with the conversion of Cr(VI) to Cr(III) in solution. In addition, the possible intermediate products and the photocatalytic reaction mechanism are revealed in depth. This work provides a general example for improving the photocatalytic activity of 2D-2D based heterojunctions by introducing a biomass material.

Compositional Dependence of Phase Selection in CoCrCu0.1FeMoNi-Based High-Entropy Alloys.

To study the effect of alloy composition on phase selection in the CoCrCu0.1FeMoNi high-entropy alloy (HEA), Mo was partially replaced by Co, Cr, Fe, and Ni. The microstructures and phase selection behaviors of the CoCrCu0.1FeMoNi HEA system were investigated. Dendritic, inter-dendritic, and eutectic microstructures were observed in the as-solidified HEAs. A simple face centered cubic (FCC) single-phase solid solution was obtained when the molar ratio of Fe, Co, and Ni was increased to 1.7 at the expense of Mo, indicating that Fe, Co, and Ni stabilized the FCC structure. The FCC structure was favored at the atomic radius ratio δ ≤ 2.8, valence electron concentration (VEC) ≥ 8.27, mixing entropy ΔS ≤ 13.037, local lattice distortion parameter α2 ≤ 0.0051, and ΔS/δ² > 1.7. Mixed FCC + body centered cubic (BCC) structures occurred for 4.1 ≤ δ ≤ 4.3 and 7.71 ≤ VEC ≤ 7.86; FCC or/and BCC + intermetallic (IM) mixtures were favored at 2.8 ≤ δ ≤ 4.1 or δ > 4.3 and 7.39 < VEC ≤ 8.27. The IM phase is favored at electronegativity differences greater than 0.133. However, ΔS, α2, and ΔS/δ² were inefficient in identifying the (FCC or/and BCC + IM)/(FCC + BCC) transition. Moreover, the mixing enthalpy cannot predict phase structures in this system.