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Atomic Structure01:33

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Atoms — and the protons, neutrons, and electrons that compose them — are extremely small. For example, a carbon atom weighs less than 2 × 10−23 g. When describing the properties of tiny objects such as atoms, we use appropriately small units of measure, such as the atomic mass unit (amu). The amu was originally defined based on hydrogen, the lightest element, then later in terms of oxygen. Since 1961, it has been defined with regard to the most abundant isotope of carbon, atoms of which...
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Activation energy is the minimum amount of energy necessary for a chemical reaction to move forward. The higher the activation energy, the slower the rate of the reaction. However, adding heat to the reaction will increase the rate, since it causes molecules to move faster and increase the likelihood that molecules will collide. The collision and breaking of bonds represents the uphill phase of a reaction and generates the transition state. The transition state is an unstable high-energy state...
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An atomic orbital represents the three-dimensional regions in an atom where an electron has the highest probability to reside. The radial distribution function indicates the total probability of finding an electron within the thin shell at a distance r from the nucleus. The atomic orbitals have distinct shapes which are determined by l, the angular momentum quantum number. The orbitals are often drawn with a boundary surface, enclosing densest regions of the cloud.
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The mathematical expression known as the wave function, ψ, contains information about each orbital and the wavelike properties of electrons in an isolated atom. When atoms are bound together in a molecule, the wave functions combine to produce new mathematical descriptions that have different shapes. This process of combining the wave functions for atomic orbitals is called hybridization and is mathematically accomplished by the linear combination of atomic orbitals. The new orbitals that...
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In an atom, the negatively charged electrons are attracted to the positively charged nucleus. In a multielectron atom, electron-electron repulsions are also observed. The attractive and repulsive forces are dependent on the distance between the particles, as well as the sign and magnitude of the charges on the individual particles. When the charges on the particles are opposite, they attract each other. If both particles have the same charge, they repel each other.
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Synthesis and Performance Characterizations of Transition Metal Single Atom Catalyst for Electrochemical CO2 Reduction
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用于CO2激活的Ni单原子催化剂

Marie-Mathilde Millet1, Gerardo Algara-Siller1, Sabine Wrabetz1

  • 1Department of Inorganic Chemistry , Fritz-Haber-Institut der Max-Planck-Gesellschaft , Faradayweg 4-6 , 14195 Berlin , Germany.

Journal of the American Chemical Society
|January 15, 2019
PubMed
概括

单原子催化剂激活二氧化碳 (CO2) 进行逆水气转移反应. 然而,孤立的原子不能进一步化产品,这突显了复杂反应的单原子催化极限.

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科学领域:

  • 材料科学
  • 催化剂
  • 表面化学

背景情况:

  • 由于最大的原子利用,单原子催化剂 (SAC) 具有独特的反应性.
  • 对于催化剂设计来说,了解孤立的金属原子与集群的作用至关重要.
  • 二氧化碳转化是碳捕获和利用的一个关键过程.

研究的目的:

  • 调查二氧化碳激活的单原子催化剂 (SAC) 的催化活性.
  • 阐明反应机制并确定二氧化碳转化的活性位点.
  • 在二氧化碳化反应中评估Ni SAC的稳定性和限制.

主要方法:

  • 通过Ni2+在MgO中的固体溶液合成Ni SAC.
  • 使用X射线光电子光谱 (XPS) 和微热量计进行表征.
  • 使用混合功能计算的计算建模.
  • 在现场进行二氧化碳转化和化的催化试验.

主要成果:

  • 原子优先占据MgO的低协调表面位置.
  • 通过逆水气转移 (rWGS) 反应,Ni SAC有效催化二氧化碳转化为二氧化碳.
  • 碳化合物形成率与表面度呈现线性相关性.
  • 在反应过程中没有观察到Ni集群形成,Ni SACs在100多小时内保持稳定.
  • 将二氧化碳化为CH4或甲醇需要Ni集群,而不是孤立的Ni原子.
  • 表面碳酸盐的形成和分解与Ni聚合有关.

结论:

  • 原子分散的Ni在MgO上作为CO2激活和rWGS的活性位点.
  • 隔离的Ni原子不足以用于随后的化步骤,这表明SACs对复杂的转换有局限性.
  • 已证明Ni SAC的稳定性,但在反应条件下可以发生聚合.
  • 这项工作提供了关于二氧化碳利用和SAC边界的基本见解.