TY - JOUR
T1 - Hydrogen adsorption and absorption on a Pd-Ag alloy surface studied using in-situ X-ray photoelectron spectroscopy under ultrahigh vacuum and ambient pressure
AU - Tang, Jiayi
AU - Yamamoto, Susumu
AU - Koitaya, Takanori
AU - Yoshikura, Yuki
AU - Mukai, Kozo
AU - Yoshimoto, Shinya
AU - Matsuda, Iwao
AU - Yoshinobu, Jun
N1 - Funding Information:
This study was supported by the Advanced-Catalytic-Transformation program for Carbon utilization (ACT-C) of the Japan Science and Technology Agency ( JST , Grant No. JPMJCR12YU ), and JSPS Grand-in-Aid for Scientific Research on Innovative Area (“3D Active-Site Science”, Grant No. 17H05212 ), and JSPS Grant-in-Aid for Young Scientists (A) (No. 16H06027 ). The synchrotron radiation UHV-XPS experiments were performed under the approval of the Photon Factory Program Advisory Committee (Proposal No. 2015S2-008). The AP-XPS measurement using synchrotron radiation were carried out at SPring-8 BL07LSU as joint research in the Synchrotron Radiation Research Organization and The Institute for Solid State Physics, The University of Tokyo (Proposal No. 2016B7401, 2017A7401, 2017B7401). The PdAg alloy sample was supplied by Tanaka Kikinzoku Kogyo K.K. The sample measurements tests and preparations for synchrotron-radiation UHV-XPS experiments were performed at SPring-8 BL23SU with the approval of the Japan Synchrotron Radiation Research Institute (Proposal Nos. 2017A3835, 2017A3801, 2017B3801).
Publisher Copyright:
© 2018 Elsevier B.V.
PY - 2019/1/1
Y1 - 2019/1/1
N2 - The hydrogen permeation process is crucial for hydrogen purification through a metal alloy. At the initial stage, it is connected with the dissociation and adsorption of hydrogen on the surface; subsequently, the process involves hydrogen absorption in the bulk. On the PdAg 23 alloy, we investigated the mechanisms of adsorption and absorption by in-situ ultrahigh vacuum and ambient pressure X-ray photoelectron spectroscopy (AP-XPS) measurements, respectively. During the adsorption under a H 2 pressure of 5 × 10 −8 Torr at 300–620 K, the surface Ag atoms act as adsorption sites for the hydrogen atoms. The AP-XPS results show that hydrogen absorption is significantly enhanced above 473 K under H 2 exposure at 1.5 Torr, which is likely correlated to the α-β hydride phase transition occurring around 473 K. Hydrogen preferentially bonds with the Pd atoms rather than the Ag atoms in the case of hydrogen absorption into the PdAg 23 alloy. The atomic fractions of Pd on the surface were enhanced after hydrogen absorption, and hydrogen adsorption at a hydrogen pressure of 5 × 10 −8 Torr at 620 K. This surface segregation of Pd atoms provides more reactive sites for hydrogen absorption, which may promote the hydrogen permeability of a PdAg 23 alloy.
AB - The hydrogen permeation process is crucial for hydrogen purification through a metal alloy. At the initial stage, it is connected with the dissociation and adsorption of hydrogen on the surface; subsequently, the process involves hydrogen absorption in the bulk. On the PdAg 23 alloy, we investigated the mechanisms of adsorption and absorption by in-situ ultrahigh vacuum and ambient pressure X-ray photoelectron spectroscopy (AP-XPS) measurements, respectively. During the adsorption under a H 2 pressure of 5 × 10 −8 Torr at 300–620 K, the surface Ag atoms act as adsorption sites for the hydrogen atoms. The AP-XPS results show that hydrogen absorption is significantly enhanced above 473 K under H 2 exposure at 1.5 Torr, which is likely correlated to the α-β hydride phase transition occurring around 473 K. Hydrogen preferentially bonds with the Pd atoms rather than the Ag atoms in the case of hydrogen absorption into the PdAg 23 alloy. The atomic fractions of Pd on the surface were enhanced after hydrogen absorption, and hydrogen adsorption at a hydrogen pressure of 5 × 10 −8 Torr at 620 K. This surface segregation of Pd atoms provides more reactive sites for hydrogen absorption, which may promote the hydrogen permeability of a PdAg 23 alloy.
KW - Absorption
KW - Adsorption
KW - Ambient-pressure
KW - Hydrogen
KW - PdAg alloy
KW - X-ray photoelectron spectroscopy
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U2 - 10.1016/j.apsusc.2018.07.078
DO - 10.1016/j.apsusc.2018.07.078
M3 - Article
AN - SCOPUS:85053491672
VL - 463
SP - 1161
EP - 1167
JO - Applied Surface Science
JF - Applied Surface Science
SN - 0169-4332
ER -