电化学界面化学吸附层--金电极上铜层的电子结构
Electronic Structure of a Chemisorbed Layer at Electrochemical Interface: Copper Layer on Gold Electrode
摘要：
一个适当的模型哈密顿为基础的形式主义提出了一个随机的吸附层与任意的覆盖率和随后的二维带形成的金属吸附在单层政权。相干势近似被用来处理随机性。明确地使用状态密度的基板带的吸附物自能进行评估。这使我们超越了传统的宽带近似，并消除了与结合能计算相关的对数发散。将该理论应用于铜离子在金电极上的电吸附，确定了吸附物电荷、结合能和吸附物态密度与覆盖度的关系。分析预测了一个独特的电荷配置的铜吸附物，具有净正电荷，在高覆盖率制度，和多个电荷状态时，覆盖率低。虽然铜的电荷构型之一在小覆盖率下接近中性，但其正电荷状态在整个覆盖率范围内是最稳定的。过渡从相对中性状态的铜在低覆盖率的正电荷配置急剧发生在中间覆盖区域。这种转变是由于铜离子随着覆盖度的增加而逐渐去溶剂化造成的。能量计算表明，铜的s-轨道键合对金属-真空界面的结合能贡献最大，而铜的d-轨道键合使金电极上的化学吸附成为可能。最后，我们的数值计算结果与相关的实验研究进行了比较。
英文摘要：
An appropriate model Hamiltonian based formalism is proposed for a random adsorbate layer with arbitrary coverage and the ensuing two-dimensional band formation by metallic adsorbates in the monolayer regime. The coherent potential approximation is employed to handle the randomness. The adsorbate self-energy is evaluated explicitly using the density of states for the substrate band. This takes us beyond the conventional wide-band approximation and removes the logarithmic divergence associated with the binding energy calculations. The formalism is applied to the electrosorption of copper ion on gold electrode, and the coverage dependence of adsorbate charge, binding energy, and adsorbate density of states are determined. The analysis predicts a unique charge configuration of copper adsorbate, having a net positive charge, in the high-coverage regime, and multiple charge states when the coverage is low. Though one of the charge configurations of copper is nearly neutral at small coverage, its positive charge state is the most stable in the entire coverage range. The transition from the relative neutral state of copper at low coverage to a positive charge configuration occurs sharply at the intermediate-coverage region. This transition is caused due to the progressive desolvation of copper adion with increasing coverage. The energy calculations show that copper s-orbital bonding contributes maximally toward the binding energy at the metal-vacuum interface, whereas it is the copper d-orbital bonding which makes chemisorption feasible at the gold electrode. Finally, our numerical results are compared with the relevant experimental studies.
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