Nature of Reaction Intermediates and Origin of Bifunctionality in Manganese Oxide
Nature of Reaction Intermediates and Origin of Bifunctionality in Manganese Oxide
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反应中间体的性质和氧化锰双官能团的起源
DOI：
10.1021/acs.jpcc.0c00714
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发表时间：
2020-02
影响因子：
3.7
通讯作者：
Indroneil Roy;Qi Wang;V. Chakrapani
中科院分区：
文献类型：
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作者：
Indroneil Roy;Qi Wang;V. Chakrapani
能够同时催化氧还原反应（ORR）和氧析反应（OER）的双功能催化剂在再生燃料电池和金属-空气电池等氧基能量转换装置中具有重要的应用价值。然而，这种催化剂产生双功能的潜在性质尚不清楚，也未被探索。我们首次使用近红外光致发光光谱技术，结合原位重量和电阻测量，跟踪电催化过程中单个金属阳离子价态的变化，揭示了在各种双功能和非双功能表面上，催化活性、电位依赖电阻和反应中间体性质之间的潜在相关性。结果表明，在OER和ORR过程中，双功能MnOx可逆地将电极性从p型转换为n型，同时形成高价阳离子Mn4+活性位点和低价阳离子Mn2+活性位点。
Bifunctional catalysts capable of catalyzing both oxygen reduction reaction (ORR) and oxygen evolution (OER) reaction are extremely valuable for oxygen-based energy conversion devices such as regenerative fuel cells and metal–air batteries. However, the underlying property of such catalysts that gives rise to their bifunctionality is not yet known nor explored. With the first use of near-infrared photoluminescence spectroscopy for tracking the changes in the individual metal cation valence states during electrocatalysis in combination with in situ gravimetric and resistance measurements, we show the underlying correlation between catalytic activity, potential-dependent resistance, and nature of reaction intermediates on various bifunctional and nonbifunctional surfaces. Our results show that bifunctional MnOx reversibly switches electrical polarity from p-type to n-type along with the formation of high-valent cationic Mn4+ active sites as well as low-valent cationic Mn2+ active sites during OER and ORR, r...