Potential-Dependent Restructuring and Hysteresis in the Structural and Electronic Transformations of Pt/C, Au(Core)-Pt(Shell)/C, and Pd(Core)-Pt(Shell)/C Cathode Catalysts in Polymer Electrolyte Fuel

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• 作者：Shin-ichi Nagamatsu ; Takashi Arai ; Masakuni Yamamoto ; Takuya Ohkura ; Hiroyuki Oyanagi ; Takayuki Ishizaka ; Hajime Kawanami ; Tomoya Uruga ; Mizuki Tada ; Yasuhiro Iwasawa
• 刊名：The Journal of Physical Chemistry C
• 出版年：2013
• 出版时间：June 27, 2013
• 年：2013
• 卷：117
• 期：25
• 页码：13094-13107
• 全文大小：671K
• 年卷期：v.117,no.25(June 27, 2013)
• ISSN：1932-7455

文摘

Potential-dependent transformations of surface structures, Pt oxidation states, and Pt鈥揙 bondings in Pt/C, Au(core)-Pt(shell)/C (denoted as Au@Pt/C), and Pd(core)-Pt(shell)/C (denoted as Pd@Pt/C) cathode catalysts in polymer electrolyte fuel cells (PEFCs) during the voltage-stepping processes were characterized by in situ (operando) X-ray absorption fine structure (XAFS). The active surface phase of the Au@Pt/C for oxygen reduction reaction (ORR) was suggested to be the Pt₃Au alloy layer on Au core nanoparticles, while that of the Pd@Pt/C was the Pt atomic layer on Pd core nanoparticles. The surfaces of the Pt, Au@Pt and Pd@Pt nanoparticles were restructured and disordered at high potentials, which were induced by strong Pt鈥揙 bonds, resulting in hysteresis in the structural and electronic transformations in increasing and decreasing voltage operations. The potential-dependent restructuring, disordering, and hysteresis may be relevant to hindered Pt performance, Pt dissolution to the electrolyte, and degradation of the ORR activity.