Au-Ni bimetallic thin films were grown on refractory metal substrates. CO and H₂ adsorption on Au-Ni bimetallic surfaces have been studied by a combination of in situ polarization modulation infrared reflection absorption spectroscopy (PM-IRRAS), temperature-programmed desorption (TPD), and density functional theory (DFT) calculations. It is found CO desorption peak shifts from 413 K on pure Ni surfaces to 293 K on the isolated Ni atoms formed by alloying with Au atoms. The sharp decrease of CO desorption temperature on Au-Ni surfaces with increasing Au coverage is caused by the change of the favored CO adsorption sites from bridge/hollow sites on pure Ni surfaces to Ni top sites on Au-Ni bimetallic surfaces. In situ PM-IRRAS shows two CO adsorption bands on Au sites at 2119 cm⁻¹ and 2103 cm⁻¹ on Au-Ni surfaces at 80 K, which are due to CO bound on under-coordinated Au atoms and electron negatively charged Au sites modified with nearby Ni atoms, respectively. Even with the Au-Ni surface temperature at as low as 100 K, CO adsorption induced Ni surface segregation has been observed by in situ PM-IRRAS. Furthermore, DFT calculation results discover the adsorption energy of CO on Ni top sites continues to decrease with increasing Au coverage due to the geometric ensemble effect and the lowered d-band center after Ni alloying with Au. H₂ desorption temperature decreases from 363 K on pure Ni thin films to 302 K with increasing Au coverage to 0.6 ML. A new H₂ peak appears at around 170 K on the Au-Ni surfaces with Au coverages between 0.6 ML and 0.9 ML. This new H₂ TPD peak is assigned to H₂ desorption from the totally isolated Ni sites. With Au coverage above 1.5 ML, there is no any H₂ desorption detected. The combined surface science studies and DFT calculations provide new insights into the surface structure-activity correlation of Ni-base bimetallic surface alloys.

Au-Ni双金属薄膜生长在难熔金属基材上。已经通过原位偏振调制红外反射吸收光谱 (PM-IRRAS)、程序升温脱附 (TPD) 和密度泛函理论 (DFT) 计算的组合研究了 Au-Ni 双金属表面上的CO 和 H ₂吸附。发现 CO 解吸峰从纯 Ni 表面的 413 K 移至与 Au 原子形成合金形成的孤立 Ni 原子上的 293 K。随着 Au 覆盖率的增加，Au-Ni 表面上 CO 解吸温度的急剧下降是由于有利的 CO 吸附位点从纯 Ni 表面上的桥/空心位点变为 Au-Ni 双金属表面上的 Ni 顶部位点。原位 PM-IRRAS 在 2119 cm ^-1处的 Au 位点上显示了两个 CO 吸附带和 2103 cm ^-1在 80 K 的 Au-Ni 表面上，这是由于 CO 结合在配位不足的 Au 原子上和分别用附近的 Ni 原子修饰的带负电的 Au 位点。即使 Au-Ni 表面温度低至 100 K，原位 PM-IRRAS 也观察到 CO 吸附诱导 Ni 表面偏析。此外，DFT 计算结果发现，由于几何系综效应和Ni 与 Au 合金化后降低的d 带中心，CO 在 Ni 顶部位点的吸附能随着 Au 覆盖率的增加而继续降低。随着金覆盖率增加到 0.6 ML，H ₂解吸温度从纯 Ni 薄膜上的 363 K 降低到 302 K。新的 H ₂峰出现在 Au-Ni 表面的 170 K 附近，Au 覆盖范围在 0.6 ML 和 0.9 ML 之间。这个新的 H ₂ TPD 峰归因于从完全孤立的 Ni 位点的H ₂解吸。当 Au 覆盖率超过 1.5 ML 时，没有检测到任何 H ₂解吸。结合表面科学研究和 DFT 计算为镍基双金属表面合金的表面结构-活性相关性提供了新的见解。