Blocking the defect sites on ultrathin Pt nanowires with Rh atoms to optimize the reaction path toward alcohol fuel oxidation

Anodic electrocatalyst plays the core role in direct alcohol fuel cells (DAFCs), while traditional Pt-catalysts suffer from limited catalytic activity, high over potential and severe CO poisoning. Herein, by selectively depositing Rh atoms on the defective-sites of Pt nanowires (NWs), we developed a new Pt@Rh NW electrocatalyst that exhibited enhanced electrocatalytic performance for both methanol oxidation (MOR) and ethanol oxidation (EOR). Both cyclic voltammetry (CV) and in-situ infrared spectroscopy revealed that the presence of Rh atoms suppressed the generation of poisonous intermediates and completely oxidized alcohols molecule into CO₂. Atomic resolusion spherical aberration corrected high-angle annular dark field scanning transmission electron microscopy (CS-HAADF-STEM) and energy-dispersive X-ray spectroscopy (EDS) mapping analysis revealed that Rh atoms were primarily deposited on the defective sites of Pt NWs. Meanwhile, the presence of Rh atoms also modified the electronic state of Pt atoms and therefore lowered the onset potential for alcohols oxidation potential. This work gives the first clear clue on the role of the defective sites of Pt nanocatalyst poisoning, and propose that selectively blocking these sites with trace amount of Rh is an effective strategy in designing advantageous electrocatalysts.     

Templated synthesis and assembly with sustainable cellulose nanomaterial for functional nanostructure

Cellulose - Templated synthesis and assembly for nanostructured materials with tailored properties have received considerable attention. The powerful templates with predefined structures can guide...     

Transition metal decorated bismuthene for ammonia synthesis: A density functional theory study

The electrochemical nitrogen reduction reaction (NRR) for the ammonia production under ambient conditions is regarded as a sustainable alternative to the industrial Haber–Bosch process. However, the electrocatalytic systems that efficiently catalyze nitrogen reduction remain elusive. In the work, the nitrogen reduction activity of the transition metal decorated bismuthene TM@Bis is fully investigated by means of density functional theory calculations. Our results demonstrate that W@Bis delivers the best efficiency, wherein the potential-determining step is located at the last protonation step of *NH₂ + H⁺ + e^– → *NH₃ via the distal mechanism with the limiting potential U_L of 0.26 V. Furthermore, the dopants of Re and Os are also promising candidates for experimental synthesis due to its good selectivity, in despite of the slightly higher U_L of NRR with the value of 0.55 V. However, the candidates of Ti, V, Nb and Mo delivered the relative lower U_L of 0.35, 0.37, 0.41 and 0.43 V might be suffered from the side hydrogen evolution reaction. More interestingly, a volcano curve is established between U_L and valence electrons of metal elements wherein W with 4 electrons in d band located at the summit. Such phenomenon originates from the underlying acceptance-back donation mechanism. Therefore, our work provides a fundament understanding for the material design for nitrogen reduction electrocatalysis.     

Effect of spatial configuration on adhesion of 1,2-disubstituted cyclohexane derivatives

Spatial configuration has a significant effect on chemical self-assembly. However, the importance of spatial configuration in supramolecular adhesive materials has been frequently ignored. In this study, the effects of the spatial configuration on cohesion and adhesion were investigated. Owing to the diversities of the chemical structures and assembly patterns, 1,2-disubstituted cyclohexane derivatives were used in this combined experimental and theoretical investigation. The self-sorting assembly of enantiopure isomers improved cohesion but had a negative effect on adhesion. In contrast, racemic mixtures displayed stronger adhesion effects. Moreover, it was proven that the cis-configuration was more favorable for supramolecular adhesion than the trans-counterpart. In addition, the influence of the spatial configuration of 1,2-disubstituted cyclohexane derivatives could be effectively mitigated by hydrogen bond donors or acceptors. The addition of natural acids yielded three-dimensional polymeric networks, in which the spatial configuration was not the decisive factor for supramolecular adhesion.     

Ethylene glycol-regulated ammonium vanadate with stable layered structure and favorable interplanar spacing as high-performance cathode for aqueous zinc ion batteries

Ammonium vanadate compounds featuring large capacity, superior rate capability and light weight are regarded as promising cathode materials for aqueous zinc ion batteries (AZIBs). However, the controllable synthesis of desired ammonium vanadates remains a challenge. Herein, various ammonium vanadate compounds were successfully prepared by taking advantage of ethylene glycol (EG) regulated polyol-reduction strategy and solvent effect via hydrothermal reaction. The morphology and crystalline phase of resultant products show an evolution from dendritic (NH₄)₂V₆O₁₆ to rod-like NH₄V₄O₁₀ and finally to lamellar (NH₄)₂V₄O₉ as increasing the amount of EG. Specifically, the NH₄V₄O₁₀ product exhibits a high initial capacity of 427.5 mAh/g at 0.1 A/g and stable cycling with a capacity retention of 90.4% after 5000 cycles at 10 A/g. The relatively excellent electrochemical performances of NH₄V₄O₁₀ can be ascribed to the stable open-framework layered structure, favorable (001) interplanar spacing, and peculiar rod-like morphology, which are beneficial to the highly reversible Zn²⁺ storage behaviors. This work offers a unique way for the rational design of high-performance cathode materials for AZIBs.     

A Subtle Change in the Flexible Achiral Spacer Does Matter in Supramolecular Chirality: Two-Fold Odd-Even Effect in Polymer Assemblies

Precise control over the chirality and morphologies of polymer assemblies, a remaining challenge for both chemists and materials scientists, is receiving ever-increasing attention in the recent years. Herein, we report the subtle manipulation of the achiral spacers from the chiral stereocenter to the azobenzene (Azo) unit, of which the chiroptical consistency or chiroptical inversion of self-assemblies could be successfully controlled and present “two-fold” odd-even effect. Furthermore, morphological transitions from 0D spherical micelles, 1D worms, and nanowires to 3D vesicles, spindle- and dumbbell-shaped vesicles were also unexpectedly found to exhibit odd-even correlations. These observations were collectively elucidated by mesomorphic properties, stacking modes, chiroptical dynamics, and stimuli-responsive behaviors. Negligible modifications to the spacer structures can enable remarkable modulation of supramolecular chirality and anisotropic topologies in polymer assemblies, which is of great significance for the design of complex chiral functional polymers.     

碳自掺杂石墨相氮化碳纳米片的制备及其在可见光照射下的光解水产氢性能

石墨相氮化碳(g?C3N4)由于具有对可见光吸收范围较窄和光生载流子分离效率低等缺陷,其光解水产氢活性较差。我们采用简单的一步热共聚法,以尿素和2,4,6?三氨基嘧啶(TAPD)混合物为前驱物,制备碳自掺杂纳米片(CNNS?x,x mg代表掺入TAPD的质量)。X射线衍射(XRD)、元素分析(EA)和X射线光电子能谱(XPS)等测试结果表明,来自TAPD的嘧啶环成功引入g?C3N4共轭体系中,使所得的CNNS?x具有较窄的带隙,较快的光生载流子迁移速率,从而提高其对可见光的吸收效率和光生载流子的分离效率。得益于此,CNNS?x在可见光照射下表现出较好的光解水产氢活性。特别是CNNS?30具有最佳光解水性能,其产氢速率可达57.6μmol·h-1,是g?C3N4纳米片(CNNS)的4倍。     

Electrical conductivity,optical properties and mechanical stability of 3, 4, 9, 10-perylenetetracarboxylic dianhidride based organic semiconductor

The 3, 4, 9, 10-perylenetetracarboxylic dianhydride (PTCDA) doped polymer films were prepared with Polypyrrole (PPy) and Polyvinyl alcohol (PVA) polymers by solution-casting. The change in structure and chemical composition of samples was identified by XRD and FTIR respectively. The UV–visible spectroscopy demonstrates the optical characteristics and band gap properties of sample. The homogeneous morphology of sample for higher wt% of PTCDA was examined by atomic force microscopy (AFM). The differential scanning calorimetry (DSC) results demonstrate the decrease in melting temperature (T_m) and degree of crystallinity (χ_c%) of polymeric organic semiconductor. The mechanical property demonstrates the high tensile strength and improved plasticity nature. Impedance spectroscopy was evaluated to determine the conductivity response of polymeric organic semiconductor. The highest DC conductivity (2.08×10⁻³ S/m) was obtained for 10 wt% of PTCDA at 140 °C. The decrease in activation energy (E_a) represents the non-Debye process and was evaluated from the slope of ln σ_dc vs. 10³/T plot.     

Optimizing the optical field distribution of near-field SIL optical storage system using five-zone binary phase filters

Five-zone binary phase filters (FBPFs) are proposed for decreasing the spot size and/or increasing the focal depth of the near-field optical storage system with a hemisphere solid immersion lens (SIL). The design of filters is based on the vector diffraction theory and the MATLAB optimizing toolbox. Three FBPFs with rotationally symmetrical pupil function have been designed, where the one FBPF is for increasing the focal depth as big as possible, the second FBPF is for improving the resolution as high as possible, and the third FBPF integrate the increase of focal depth with the improvement of resolution. Numerical results show that compared with the three-zone amplitude filter, the designed five-zone binary phase-only filters have more prominent performances in improving the focal depth and the resolution of the near-field SIL optical storage system.