Crystal phase control in two-dimensional materials

It is the nature of crystals to exist in different polymorphs. The recent emergence of two-dimensional (2D) materials has evoked the discovery of a number of new crystal phases that are different from their bulk structures at ambient conditions, and revealed novel structure-dependent properties, which deserve in-depth understanding and further exploration. In this contribution, we review the recent development of crystal phase control in 2D materials, including group V and VI. transition metal dichalcogenides (TMDs), group IVA metal chalcogenides and noble metals. For each group of materials, we begin with introducing the various existing crystal phases and their structure-related properties, followed by a detailed discussion on factors that influence these crystal structures and thus the possible strategies for phase control. Finally, after summarizing the whole paper, we present the challenges and opportunities in this research direction.     

The Synergistic Photocatalytic Effect of H3PW12O40 and Pt Nanoparticles Comodified UiO-66-NH2 on the Reduction of Aqueous Cr(VI) under Original pH

Kinetics and Catalysis - A ternary synergistic photocatalyst H3PW12O40/Pt/UiO-66-NH2 was successfully fabricated for the first time through a simple solvothermal synthetic strategy. We found that...     

介质阻挡放电甲醇脱氢偶联一步合成乙二醇反应中氢气的催化作用

利用原位发射光谱表征和在线色谱分析,研究了甲醇介质阻挡放电脱氢偶联一步合成乙二醇反应中氢气的催化作用,考察了放电频率、甲醇和氢气进料量以及反应压力的影响.结果表明,在介质阻挡放电产生的非平衡等离子体中,H2不但能显著提高甲醇转化率,而且能显著提高乙二醇的选择性.在300°C,0.1 MPa,反应器注入功率为11 W,放电频率为12.0 k Hz,甲醇气体进料量为11.1 m L/min,氢气进料量为80–180 m L/min的条件下,甲醇转化率接近30%,乙二醇选择性大于75%.乙二醇收率与激发态氢原子的Hα谱线强度之间存在同增同减关系.由此推测,氢原子是起催化作用的活性氢物种.活性氢物种的生成途径是:基态氢分子通过与电子碰撞变成激发态,激发态氢分子通过第一激发态氢自动解离为基态氢原子.放电反应条件通过影响氢分子解离来影响氢气的催化作用.氢气在非平衡等离子体中显示的催化作用有可能为开辟新的化学合成途径提供重要机遇.     

Solvent induced enhancement of nonlinear optical response of graphdiyne

Flat and crystalline materials with exceptional nonlinear optical(NLO) properties are highly desirable for their potential applications in integrated NLO photonic devices.Graphdiyne(GD),a new twodimensional(2 D) carbon allotrope,has recently evoked burgeoning research attention by virtue of its tunable bandgap along with a high carrier mobility and extended π-conjugation compared with most conventional optical materials.Here,we experimentally probe the third-order nonlinear optical response of GD dispersed in several common solvents(alcohols) using a femtosecond Z-scan technique.The measured nonlinear optical refractive index is in the order of ~10^-8 cm²/W,which is approximately one order of magnitude higher than that of most 2 D materials.In particular,we find that different NLO responses can be observed from GD when dispersed in different solvents,with the strongest NLO response when dispersed in 1-propanol.It is proposed that some intrinsic properties of the solvents,such as the polarity and viscosity,could influence the NLO response of GD materials.Our experimental results confirm the assumptions on the NLO behavior in GD and demonstrate its great potential for future generations of Kerr-effect-based NLO materials and devices.     

Functional molecular materials

正Molecular materials,together with metals,ceramics,and polymer materials,are among the most important materials.The research efforts on molecular materials are targeting three main aspects,namely the assembly technique,multi-functionality,and their diverse application.In this regard,the main attention from the community is focused on the identification and     

浅海波导界面对点源振速方向的影响

采用“虚源法”分析计算了浅海波导环境中接收点处点源总振速方向与水平面夹角,侧重讨论确定性界面反射对总振速方向的影响。研究结果表明：总振速方向和接收点与声源的水平距离、两者深度,海底、海面特性以及声速剖面等有关。在等声速均匀浅海波导中,由于确定性界面反射的影响,当直达声掠射角为1°～50°时,合成总振速方向偏离直达声方向达1.5°～10.5°,声速剖面呈负梯度时,偏离程度更甚.     

Nanoporous Palladium Hydride for Electrocatalytic N2 Reduction under Ambient Conditions

The electrocatalytic nitrogen reduction reaction (NRR) is an alternative eco‐friendly strategy for sustainable N₂ fixation with renewable energy. However, NRR suffers from sluggish kinetics owing to difficult N₂ adsorption and N≡N cleavage. Now, nanoporous palladium hydride is reported as electrocatalyst for electrochemical N₂ reduction under ambient conditions, achieving a high ammonia yield rate of 20.4 μg h^?1 mg^?1 with a Faradaic efficiency of 43.6 % at low overpotential of 150 mV. Isotopic hydrogen labeling studies suggest the involvement of lattice hydrogen atoms in the hydride as active hydrogen source. In situ Raman analysis and density functional theory (DFT) calculations further reveal the reduction of energy barrier for the rate‐limiting *N₂H formation step. The unique protonation mode of palladium hydride would provide a new insight on designing efficient and robust electrocatalysts for nitrogen fixation.