Abnormal Metal Bond Distances in PtAu Alloy Nanoparticles: In Situ Back-Illumination XAFS Investigations of the Structure of PtAu Nanoparticles on a Flat HOPG Substrate Prepared by Arc Plasma Deposition
Abnormal Metal Bond Distances in PtAu Alloy Nanoparticles: In Situ Back-Illumination XAFS Investigations of the Structure of PtAu Nanoparticles on a Flat HOPG Substrate Prepared by Arc Plasma Deposition
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PtAu 合金纳米粒子中的异常金属键距：原位背照式 XAFS 研究电弧等离子体沉积制备的平面 HOPG 基底上 PtAu 纳米粒子的结构
DOI：
10.1021/acs.jpcc.1c08393
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发表时间：
2022
期刊：
影响因子：
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通讯作者：
Asakura Kiyotaka
中科院分区：
文献类型：
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作者：
Hu Bing;Bharate Bapurao;Jimenez Juan D.;Lauterbach Jochen;Todoroki Naoto;Wadayama Toshimasa;Higashi Kotaro;Uruga Tomoya;Iwasawa Yasuhiro;Ariga-Miwa Hiroko;Takakusagi Satoru;Asakura Kiyotaka
为了揭示Au（核）-Pt（壳）型（PtAu）纳米颗粒中Pt-Pt键距与Au（111）上的Pt覆盖层中Pt-Pt键距差异的根源，通过电弧等离子体沉积在高取向热解石墨（HOPG）表面上制备了合金型PtAu纳米颗粒，并在不同的电化学条件下研究了它们的结构 弯曲晶体劳厄分析仪（BCLA）支持的背照式X射线吸收精细结构（BCLA + BI-XAFS）和高能分辨率荧光检测（HERFD）支持的背照式X射线吸收近边缘结构（HERFD + BI-XANES）方法。基于两侧边缘的 XAFS 分析，我们提出在 0.4 VRHE 下形成覆盖有富 Pt 壳的 PtAu 合金核，其中 Pt-Pt、Pt-Au 和 Au-Au 键长均约为 2.76 Å。 Au-Au 键长异常短于块状 Au。在高强度 X 射线的帮助下，在大于 0.8 VRHE 的外加电势下，Pt 壳溶解，Au-Au 距离增加。我们得出的结论是，异常的键长是由于富铂壳的强表面张力和晶格畸变的松弛造成的。 PtAu 纳米颗粒中的 Pt-Pt 键长由于纳米颗粒的表面张力而减小；这种表面张力在平坦的 Au 表面上不存在，其中 Pt 覆盖层和基底之间的晶格畸变是 Pt-Pt 键长扩展的主要驱动力。
To reveal the origin of the difference between the Pt–Pt bond distance in Au(core)–Pt(shell)-type (PtAu) nanoparticles and that in a Pt overlayer on Au(111), alloy-type PtAu nanoparticles were prepared on a highly oriented pyrolytic graphite (HOPG) surface by arc plasma deposition and their structure was investigated under various electrochemical conditions by bent-crystal Laue analyzer (BCLA)-empowered back-illuminated X-ray absorption fine structure (BCLA + BI-XAFS) and high-energy-resolution fluorescence detection (HERFD)-empowered back-illuminated X-ray absorption near-edge structure (HERFD + BI-XANES) methods. On the basis of the XAFS analysis at both edges, we proposed the formation of a PtAu alloy core covered with a Pt-rich shell at 0.4 VRHE, where the Pt–Pt, Pt–Au, and Au–Au bond lengths were all found to be ∼2.76 Å. The Au–Au bond length was abnormally shorter than that for bulk Au. The Pt shell was dissolved under applied potentials greater than 0.8 VRHEwith the aid of the high-intensity X-rays, and the Au–Au distance increased. We concluded that the abnormal bond lengths were due to the strong surface tension from the Pt-rich shell and the relaxation of the lattice distortion. The Pt–Pt bond length in the PtAu nanoparticles decreases as a result of the surface tension of the nanoparticles; this surface tension does not exist on flat Au surfaces, where the lattice distortion between the Pt overlayer and the substrate is the main driving force for the expansion of the Pt–Pt bond length.