Abstract

A study on the molecular adsorption of a water (H₂O) monomer on Pt alloy surfaces with binary Pt-Ru and Pt-Mo and ternary Pt-Ru-Mo surface models was conducted. Some calculations of the interaction between a H₂O monomer and the Pt surface were also done for reference. This study is based on density functional theory (DFT) with periodic models and aims to understand the H₂O adsorption mechanism. In Pt, Pt-Ru, and Pt-Mo surfaces, H₂O preferably adsorbs via an oxygen atom in a flat configuration at the top sites of Pt, Ru, Mo, respectively. However, on the ternary Pt-Ru-Mo surface, the adsorption configuration has the most inclined H₂O structure relative to the surface. The results showed that the binding energy of H₂O/Pt-Ru-Mo > H₂O/Pt-Mo > H₂O/Pt-Ru > H₂O/Pt. The adsorption mechanism was then clarified by charge transfer and natural bonding. The charge transfer from the surface to the adsorbate is observed in all models, with the greatest charge transfer occurring on the surface of Pt doped with two Mo atoms. This is probably due to the fact that oxygen can attract the most charge on Mo, because the difference in electronegativity is greatest. The calculation results also show that Ru is the most hydrophilic metal for oxygen. However, since the adsorption structure is parallel to the surface, hydrogen (H) is also more sensitive to receive the charge. Subsequently, the most acceptable reason for the most stable adsorption for H₂O/Pt-Ru-Mo is that the inclined structure yields the most orbitals hybridization at the H₂O's highest occupied molecular orbital (HOMO). This drives the interaction by forming bonding states at the lowest energy and anti-bonding states at the highest energy.

中文翻译：

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钌和钼合金Pt（111）表面吸附H 2 O的第一性原理研究

摘要

利用二元Pt-Ru和Pt-Mo以及三元Pt-Ru-Mo表面模型研究了水（H ₂ O）单体在Pt合金表面上的分子吸附。还对H ₂ O单体与Pt表面之间的相互作用进行了一些计算，以供参考。这项研究基于具有周期性模型的密度泛函理论（DFT），旨在了解H ₂ O的吸附机理。在Pt，Pt-Ru和Pt-Mo表面中，H ₂ O优选通过氧原子以平面构型分别吸附在Pt，Ru，Mo的顶部部位。然而，在三元Pt-Ru-Mo表面上，吸附构型具有最倾斜的H _2。相对于表面的O结构。结果表明，H ₂ O / Pt-Ru-Mo> H ₂ O / Pt-Mo> H ₂ O / Pt-Ru> H _{2的结合能}选择。然后通过电荷转移和自然键合阐明了吸附机理。在所有模型中都观察到了从表面到吸附物的电荷转移，其中最大的电荷转移发生在掺杂有两个Mo原子的Pt表面上。这可能是由于氧的电负性差异最大，因此氧可以在Mo上吸引最多的电荷。计算结果还表明，Ru是氧最亲水的金属。但是，由于吸附结构与表面平行，因此氢（H）对接收电荷也更敏感。随后，最稳定地吸附H ₂ O / Pt-Ru-Mo的最可接受的理由是，倾斜结构在H ₂处产生的轨道杂交最多O的最高占据分子轨道（HOMO）。这通过在最低能量下形成键合状态和在最高能量下形成反键合状态来驱动相互作用。