For decades, it has been recognized that alloying platinum (Pt) with a secondary metal can enhance the catalytic activity of the oxygen reduction reaction (ORR) compared to pristine Pt catalysts. However, the mechanisms underlying this phenomenon vary significantly from one alloy to another. Here, we report the results of a computational study on the origin of the experimentally observed enhanced ORR activity of AgPt/Pt(111) monolayer surface alloy with 7 %–50 % Ag contents. A phase-separation model was developed and able to generate 2D phase-separation distributions of Ag and Pt atoms in AgPt/Pt(111) surfaces in line with atomic resolution scanning tunneling microscopy. We employed DFT-calculated *OH adsorption energy as a descriptor to obtain the activity of those surfaces, which reveals the ORR activity dominated by the reaction on Pt(Pt) heptamers and also gives evidence of long-range self-induced surface strain as the source of the enhanced activity of binary AgPt/Pt(111) surfaces, i.e., the slightly larger surface Ag atoms induce a compressive strain of Pt-Pt bonds of the Pt(Pt) heptamers, which increases the activity of binary surfaces compared to the pristine Pt(111) surface. Moreover, the excellent simulated-experimental agreement for the polarization curves shows the high quality of this approach and its more general potential for an improved understanding of the catalytic properties of inhomogeneous binary surfaces as the basis for a rational design of binary catalysts.

中文翻译：

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自诱导的长程表面应变改善了氧还原反应

几十年来，人们已经认识到，与原始 Pt 催化剂相比，将铂 (Pt) 与辅助金属合金化可以增强氧还原反应 (ORR) 的催化活性。然而，这种现象背后的机制因合金而异。在这里，我们报告了对实验观察到的Ag含量为7%–50%的AgPt/Pt(111)单层表面合金增强ORR活性的起源的计算研究结果。开发了相分离模型，能够生成 AgPt/Pt(111) 表面中 Ag 和 Pt 原子的二维相分离分布，与原子分辨率扫描隧道显微镜一致。我们使用 DFT 计算的 *OH 吸附能作为描述符来获得这些表面的活性，这揭示了 ORR 活性由 Pt(Pt) 七聚体上的反应主导，并且还提供了长程自诱导表面应变作为二元AgPt/Pt(111)表面活性增强的来源，即稍大的表面Ag原子诱导Pt(Pt)七聚体的Pt-Pt键的压缩应变，与二元表面相比，这增加了二元表面的活性原始的 Pt(111) 表面。此外，极化曲线的出色模拟实验一致性表明了该方法的高质量及其更广泛的潜力，可以更好地理解不均匀二元表面的催化性能，作为二元催化剂合理设计的基础。