Size-Dependent Activity Trends Combined with in Situ X-ray Absorption Spectroscopy Reveal Insights into Cobalt Oxide/Carbon Nanotube-Catalyzed Bifunctional Oxygen Electrocatalysis

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• 作者：Bora Seo ; Young Jin Sa ; Jinwoo Woo ; Kyungjung Kwon ; Jongnam Park ; Tae Joo Shin ; Hu Young Jeong ; Sang Hoon Joo
• 刊名：ACS Catalysis
• 出版年：2016
• 出版时间：July 1, 2016
• 年：2016
• 卷：6
• 期：7
• 页码：4347-4355
• 全文大小：629K
• 年卷期：0
• ISSN：2155-5435

文摘

Bifunctional oxygen electrocatalysts play a vital role in important energy conversion and storage devices. Cost-effective, abundant, and active Co-based materials have emerged as promising bifunctional electrocatalysts for which identifying catalytically active structures under reaction conditions and unraveling the structure–activity relationships are of critical importance. Here, we report the size-dependent (3–10 nm) structure and catalytic activity of bifunctional cobalt oxide nanoparticle (CoO_x NP) catalysts for the oxygen evolution reaction (OER) and the oxygen reduction reaction (ORR). In situ X-ray absorption spectroscopy (XAS) revealed that the majority of NPs during OER and ORR were composed of the Co₃O₄ and CoOOH phases regardless of their particle sizes. The OER activity increased with decreasing NP size, which correlated to the increased oxidation state and larger surface area in smaller NPs, whereas the ORR activity was nearly independent of NP size. These particle size-dependent catalytic activities in conjunction with the in situ XAS results can provide insights into the CoO_x-catalyzed bifunctional oxygen electrode reactions.