Overpotential-Induced Introduction of Oxygen Vacancy in La0.67Sr0.33MnO3 Surface and Its Impact on Oxygen Reduction Reaction Catalytic Activity in Alkaline Solution

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• 作者：Daisuke Kan ; Yuki Orikasa ; Kiyofumi Nitta ; Hajime Tanida ; Ryo Kurosaki ; Tomoe Nishimura ; Takahiro Sasaki ; Haichuan Guo ; Yusuke Ozaki ; Yoshiharu Uchimoto ; Yuichi Shimakawa
• 刊名：Journal of Physical Chemistry C
• 出版年：2016
• 出版时间：March 24, 2016
• 年：2016
• 卷：120
• 期：11
• 页码：6006-6010
• 全文大小：323K
• ISSN：1932-7455

文摘

Oxygen reduction reaction (ORR) catalytic activity of La_0.67Sr_0.33MnO₃ epitaxial thin films was investigated in a KOH solution by using a rotating-disk electrode. We found that while the films exhibit ORR current, the current is not limited by oxygen transport resulting from the film electrode rotation and shows the large hysteresis against the potential sweep direction. This behavior is in stark contrast to the oxygen reduction reaction activity of an electrode ink made from LSMO bulk powder, whose ORR current is oxygen-transport limited. In situ synchrotron X-ray absorption spectroscopy also reveals that the valence state of Mn in the LSMO film surface is lowered under the reducing atmosphere caused by the overpotential. This indicates the overpotential-induced introduction of oxygen vacancies in the film surface. We also show that the ORR current of the LSMO films exposed to the reducing atmosphere is lowered than that of the original surface. These results indicate that the ORR catalytic activity of LSMO surfaces is strongly influenced by oxygen vacancies.