Understanding the chemisorption of atoms on precious metal surfaces is of substantial interest for the rational design of heterogeneous and electrochemical catalysts. In this study, we report density functional theory (DFT) investigations of the chemisorption of atomic H and O on bimetallic Pt x Ir y (111) surfaces for bifunctional anode catalyst materials in polymer electrolyte membrane (PEM) fuel cells. We found that for both adsorbates, the adsorption on the Pt(111) surface is in general less exothermic than on the Ir(111) surface. Our study has revealed that chemisorption on the bimetallic surfaces becomes more stable with increasing number of Ir surface atoms at the adsorption site. While for hydrogen atoms the ONTOP sites yield the most negative adsorption energies, the chemisorption of oxygen atoms appears to be most stable on the FCC sites for both the mono- and bimetallic surfaces. Using the ab initio thermodynamics approach, we calculated phase diagrams for the chemisorption of H and O atoms on these metal surfaces in order to transfer our findings to finite temperature and pressure conditions. Our theoretical results may provide an improved understanding of the hydrogen oxidation reaction (HOR) and oxygen evolution reaction (OER) on intermetallic Pt x Ir y (111) surfaces and may be helpful for the rational design of new bifunctional PEM fuel cell anode catalyst materials.

中文翻译：

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从头计算原子 H 和 O 在 Pt 和 Ir 金属以及双金属 Pt x Ir y 表面上的化学吸附

了解原子在贵金属表面上的化学吸附对于合理设计多相催化剂和电化学催化剂具有重要意义。在这项研究中，我们报告了双金属 Pt 上原子 H 和 O 化学吸附的密度泛函理论 (DFT) 研究 X 红外线 y （111）聚合物电解质膜（PEM）燃料电池中双功能阳极催化剂材料的表面。我们发现，对于两种吸附物，Pt(111) 表面上的吸附通常比 Ir(111) 表面上的吸附放热少。我们的研究表明，随着吸附位点上铱表面原子数量的增加，双金属表面上的化学吸附变得更加稳定。对于氢原子来说，ONTOP 位点产生最负的吸附能，而对于单金属和双金属表面，氧原子的化学吸附似乎在 FCC 位点上最稳定。使用从头开始利用热力学方法，我们计算了这些金属表面上 H 和 O 原子化学吸附的相图，以便将我们的发现转移到有限的温度和压力条件下。我们的理论结果可以加深对金属间化合物 Pt 上的氢氧化反应 (HOR) 和析氧反应 (OER) 的理解 X 红外线 y (111)表面活性可能有助于新型双功能质子交换膜燃料电池阳极催化剂材料的合理设计。