Dirac Nodal Arc Semimetal PtSn4: An Ideal Platform for Understanding Surface Properties and Catalysis for Hydrogen Evolution

Conductivity, carrier mobility, and a suitable Gibbs free energy are important criteria that determine the performance of catalysts for a hydrogen evolution reaction (HER). However, it is a challenge to combine these factors into a single compound. Herein, we discover a superior electrocatalyst for a HER in the recently identified Dirac nodal arc semimetal PtSn₄. The determined turnover frequency (TOF) for each active site of PtSn₄ is 1.54 H₂ s^?1 at 100 mV. This sets a benchmark for HER catalysis on Pt‐based noble metals and earth‐abundant metal catalysts. We make use of the robust surface states of PtSn₄ as their electrons can be transferred to the adsorbed hydrogen atoms in the catalytic process more efficiently. In addition, PtSn₄ displays excellent chemical and electrochemical stabilities after long‐term exposure in air and long‐time HER stability tests.     

考虑气压效应平流层平台柔性飞艇变形分析方法与特征研究

为研究气压对平流层飞艇变形性能的影响,基于铁木辛柯梁分析理论,将低阻尼流线形飞艇假设为分段等截面充气梁,采用叠加法推导了考虑气压效应的柔性飞艇总体挠度计算式。同时,将柔性飞艇作为预应力薄膜结构,应用ANSYS软件,采用小杨氏模量法进行充气预应力找形,并基于找形结果进行载荷下非线性变形分析。在此基础上计算了飞艇外气囊在不同头部荷载与气压下的总体挠度并比较了两种方法的计算值,发现两者变化趋势一致。最后,建立了25 m验证飞艇的计算模型,得到了控制点应力和总体变形;给出了飞艇下腹线在不同气压下的位形,将其与测量值进行比较表明:计算值和测量值基本相等,误差小于5%。本文对大型柔性飞艇设计分析具有一定的参考价值。     

14N and 45Sc NMR study of trimetallic nitride cluster (M3N)6+ dynamics inside a icosahedral C80 cage

The dynamics of the trimetallic nitride (M(3)N)(6+) (M = Sc, Y and Lu) clusters in the I(h)-(C(80))(6-) cage have been studied by (14)N and (45)Sc nuclear magnetic resonance. These NMR studies suggest that the motional barrier of (M(3)N)(6+) is related to the cluster size and increases in the series (Sc, Y, and Lu).