Tayal Akhil, Seo Okkyun, Kim Jaemyung, Kobayashi Hirokazu, Yamamoto Tomokazu, Matsumura Syo, Kitagawa Hiroshi, Sakata Osami
Deutsches Elektronen-Synchrotron, Notkestrasse 85, 22607 Hamburg, Germany.
Synchrotron X-ray Group, Research Center for Advanced Measurement and Characterization, National Institute for Materials Science, 1-1-1 Kouto, Sayo, Hyogo 679-5148, Japan.
ACS Appl Mater Interfaces. 2021 May 26;13(20):23502-23512. doi: 10.1021/acsami.0c22432. Epub 2021 May 14.
The hydrogen storage capacity of Pd nanoparticles (NPs) decreases as the particles become smaller; however, this reduced capacity is ameliorated by addition of Pt. In the present work, the hydrogen storage mechanism and structural transformations of core (Pd)-shell (Pt) (CS) and solid-solution (SS) NPs during hydrogen absorption and desorption (PHAD) processes are investigated. In situ X-ray absorption spectroscopy measurements were performed to study the evolution of electronic and local structures around Pd and Pt during PHAD. Under ambient conditions, Pd and Pt have distinct local structures. The Pd atomic pairs are more strained in CS NPs than in SS NPs. A similar behavior has been seen in CS NPs after PHAD. The Pd K-edge extended X-ray absorption fine structure data indicate that in CS and SS NPs a substantial fraction of the signal derives from Pd-Pd atomic pairs, indicating that Pd clusters remain present even after PHAD. PHAD causes a rearrangement of the interfacial structure, which becomes homogeneously distributed. The higher coverage of active bimetallic sites results in a higher observed hydrogen storage capacity in the SS phase.
随着钯纳米颗粒（NPs）尺寸变小，其储氢容量会降低；然而，通过添加铂可改善这种降低的容量。在本工作中，研究了核（钯）-壳（铂）（CS）和固溶体（SS）纳米颗粒在吸氢和解吸（PHAD）过程中的储氢机制及结构转变。进行了原位X射线吸收光谱测量，以研究PHAD过程中钯和铂周围电子结构及局部结构的演变。在环境条件下，钯和铂具有不同的局部结构。CS纳米颗粒中的钯原子对比SS纳米颗粒中的更受应变。在PHAD后的CS纳米颗粒中也观察到了类似行为。钯K边扩展X射线吸收精细结构数据表明，在CS和SS纳米颗粒中，相当一部分信号来自钯-钯原子对，这表明即使在PHAD后钯簇仍存在。PHAD导致界面结构重排，其变得均匀分布。活性双金属位点的更高覆盖率导致在SS相中观察到更高的储氢容量。
