3d transitional-metal single atom catalysis toward hydrogen evolution reaction on MXenes supports

Single atom catalysis involving atomically dispersed metal active sites on the appropriate supports is the effective way to magnify the catalytic efficiency and reduce the cost. By performing the first-principles calculations, we studied the anchoring of 3d transitional-metal single atoms M (Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu and Zn) on the surfaces of MXenes Cr₂CO₂ and Mo₂CO₂ and the catalytic activity of the single atom sites for hydrogen evolution reaction (HER). Sixteen single atom sites, M-Cr₂CO₂ (M = Sc, Ti, V, Cr, Mn, Fe, Co, Cu and Zn) and M-Mo₂CO₂ (M = Sc, Ti, V, Cr, Mn, Fe and Zn) have been chosen via examining the energetical and thermal stability of the isolated M atoms on the substrates. More importantly, we have calculated the Gibbs free energy change (ΔG_H) of H adsorption on the surface of M anchored Cr₂CO₂ and Mo₂CO₂ and find that Cr, Fe, Zn on Cr₂CO₂ and Sc, V on Mo₂CO₂ are the promising single atom active sites toward HER. Additionally, our results show that M atoms adsorbing turns the nearby sites to be active for catalyzing HER. MXenes Cr₂CO₂ and Mo₂CO₂, in terms of the supporting not only stabilize but also works together with the anchored single atom M as active catalyst toward HER.     

Preparation of nanocrystalline MoSi2 with enhanced lithium storage by sol–gel and carbonthermal reduction method

Herein nanocrystalline MoSi₂ with enhanced lithium storage was successfully synthesized via a sol-gel and carbonthermal reduction method. Reduction of the gel mixture of Mo precursor and Si precursor by carbon at a desired temperature resulted in the formation of MoSi₂ nanoparticles. The gel mixture was obtained through the hydrolysis of TEOS and ammonium molybdate and the polymerization of hydrolysis products of TEOS. The reducing agent carbon was produced via decarburition of sucrose's hydrolysis products, which have been wrapped in the gel during its formation process. Addition of HCl to the mixed solution controlled the hydrolysis and polymerization rate, and enabled the formation of a gel mixture with homogeneously distributed hydrolysis products of ammonium molybdate, TEOS and sucrose. This achievement likely generates a novel route to synthesize non-oxide compounds such as silicide, carbide through the sol–gel and carbonthermal reduction process. In addition, the as-received MoSi₂ nanoparticles showed considerable activities in the reversible lithiation and delithiation process. When using as an anode for Li-ion batteries, MoSi₂ nanoparticles delivered a specific capacity of 325 mAh g^?1 at C/12 and showed an increasing capacity with cycling.     

A multi-start central force optimization for global optimization

Central force optimization (CFO) is an efficient and powerful population-based intelligence algorithm for optimization problems. CFO is deterministic in nature, unlike the most widely used metaheuristics. CFO, however, is not completely free from the problems of premature convergence. One way to overcome local optimality is to utilize the multi-start strategy. By combining the respective advantages of CFO and the multi-start strategy, a multi-start central force optimization (MCFO) algorithm is proposed in this paper. The performance of the MCFO approach is evaluated on a comprehensive set of benchmark functions. The experimental results demonstrate that MCFO not only saves the computational cost, but also performs better than some state-of-the-art CFO algorithms. MCFO is also compared with representative evolutionary algorithms. The results show that MCFO is highly competitive, achieving promising performance.     

Self-assembly of ultralight and compressible inorganic sponges with hierarchical porosity by electrospinning

The construction of three dimensional macroporous architectures holds exciting implications for applications such as catalysis, sensing, tissue engineering and thermal insulation. Here, we report a general self-assembly process for inorganic sponges with hierarchical porosity of intrafibre micro-/meso-/macropores and interfibre macropores. The as-fabricated SiO₂-TiO₂ sponge possesses a high porosity of >99.86%, ultralow bulk density of 2.9 mg cm⁻³ and enhanced compressibility (recovery from 50% compression). The self-assembly mechanism of the SiO₂-TiO₂ sponge has been investigated in detail. The results confirmed that the hydrolysis and polycondensation of mixed inorganic alkoxides could affect the solidification process and the charge transpote during electrospinning, and plays an essential role on the hierarchical porosity and the self-assembly of the sponge macro-structure. The concerted effects of the solidification and electrostatic repulsion between fibres are responsible for the self-assembly process of the electrospun PVP-SiO₂-TiO₂ sponge. When used as a thermal insulation material, the SiO₂-TiO₂ sponge shows good fireproof performances. The current contribution may guide more construction of functional inorganic macroporous architectures for advance applications in future.     

Monomer casting nylon-6-b-polyether amine copolymers: Synthesis and properties

MC nylon-6-b-polyether amine copolymers were prepared with macro-initiator based on amino-terminated polyether amine functionalized with isocyanate via in-situ polymerization. It was found that the introduction of polyether amine delayed the polymerization process of caprolactam by increasing apparent activation energy and pre-exponential factor, resulting in the decrease of molecular weight of nylon-6. The motion of molecular chain of the copolymers was easy because of the decreased hydrogen bonds and weakened inter-molecular forces. The physical entanglement of molecular chains of the copolymers was significant and strong which increased the entanglement density. Only the nylon-6 phase crystallized in the copolymers and the crystal grain size, spherulite size and crystallinity of the copolymers decreased. A small amount of γ crystal formed at high polyether amine content. The copolymers presented obvious strain hardening behavior in stress-strain curves and the loss factor dramatically increased while the glass transition temperature and storage module decreased. The fracture surface of the copolymers became rough and presented hairy structure, indicating that the toughening mechanism of the copolymers corresponded to the multi-layer crack extension mechanism.     

A review of advanced proton-conducting materials for hydrogen separation

This paper provides a comprehensive overview of developments and recent trends in H₂ separation technology that uses dense proton–electron conducting ceramic materials and their associated membranes. Various proton–electron conducting materials and their associated membranes are summarized and classified into several important categories, such as Ni-composite proton-conducting materials, as well as tungstate-based, BaPrO₃-based, LaGaO₃-based, and niobate/tantalite composite metal oxide-based ceramic materials/membranes. Various membrane designs, including asymmetric ceramic membranes (supported and self-supported) and surface-modified membranes, are also reviewed. Several important properties of ceramic materials and membranes, such as proton and electron conductivity and performance (i.e., H₂ transport flux and lifetime stability), are also discussed. To highlight the technical progress in this area, all possible ceramic materials and associated membranes are summarized, along with their properties and performance, to help readers quickly locate the information they are looking for. Based on this review, several challenges hindering the maturation of this technology are analyzed in depth, and possible research directions for overcoming these challenges are suggested.     

车门内饰板优化分析及模具设计

利用CAE分析软件Moldex3D先找出整个设计是否存在缺陷,为了增加优化效率,采用田口实验设计法规划控制因子与配置。L9(34)直交表来求得成型条件的最佳化参数组别,观察结果并找出最佳成型条件,以降低成型后所发生的体积收缩率以及翘曲位移量。由S/N因子反应表可看出对于Z轴变形量在塑料温度209℃、保压时间11.025 s、冷却时间17.85 s时较优良。Z轴的翘曲从1.64 mm降低到1.04 mm,整体改善了36.5%,最终根据优化结果进行了模具设计。