In Situ X-ray Absorption Spectroscopy of a Synergistic Co-Mn Oxide Catalyst for the Oxygen Reduction Reaction.
In Situ X-ray Absorption Spectroscopy of a Synergistic Co-Mn Oxide Catalyst for the Oxygen Reduction Reaction.
复制标题
DOI：
10.1021/jacs.8b12243
复制
发表时间：
2019-01
影响因子：
15
通讯作者：
Yao Yang;Ying Wang;Yin Xiong;Xin Huang;Luxi Shen;Rong Huang;Hongsen Wang;J. Pastore;Seungho Y
中科院分区：
文献类型：
--
作者：
Yao Yang;Ying Wang;Yin Xiong;Xin Huang;Luxi Shen;Rong Huang;Hongsen Wang;J. Pastore;Seungho Y
在实时电化学条件下识别氧还原反应中的催化活性中心(S)对于燃料电池和其他技术的发展至关重要。我们用原位同步加速器X射线吸收光谱(XAS)研究了在碱性燃料电池中表现出令人印象深刻的ORR活性的Co-Mn氧化物催化剂的协同作用。用X射线吸收近边结构(XANES)跟踪了Co和Mn在稳态(恒定外加电位)和非稳态(动电位循环伏安，CV)下的动态结构变化。在稳态条件下，在较低的电势下，Mn和Co的价态均降低，表明Mn(III，IV)和Co(III)分别转化为Mn(II，III)和Co(II)。快速的X射线数据采集与CV中的慢扫描速度相结合，在施加的电位下实现了3 mV的分辨率，接近非稳定(动电位)状态。Co和Mn价态的变化是同时发生的，并且呈现出跟踪循环电位扫描的周期性模式。据我们所知，这是第一次利用原位XAS来解析双金属氧化物的协同催化机理。本文开发/描述的策略可以为揭示其他多金属电催化剂的反应机理提供一种有前途的方法。
Identifying the catalytically active site(s) in the oxygen reduction reaction (ORR), under real-time electrochemical conditions, is critical to the development of fuel cells and other technologies. We have employed in situ synchrotron-based X-ray absorption spectroscopy (XAS) to investigate the synergistic interaction of a Co-Mn oxide catalyst which exhibits impressive ORR activity in alkaline fuel cells. X-ray absorption near edge structure (XANES) was used to track the dynamic structural changes of Co and Mn under both steady state (constant applied potential) and nonsteady state (potentiodynamic cyclic voltammetry, CV). Under steady state conditions, both Mn and Co valences decreased at lower potentials, indicating the conversion from Mn(III,IV) and Co(III) to Mn(II,III) and Co(II), respectively. Rapid X-ray data acquisition, combined with a slow sweep rate in CV, enabled a 3 mV resolution in the applied potential, approaching a nonsteady (potentiodynamic) state. Changes in the Co and Mn valence states were simultaneous and exhibited periodic patterns that tracked the cyclic potential sweeps. To the best of our knowledge, this represents the first study, using in situ XAS, to resolve the synergistic catalytic mechanism of a bimetallic oxide. Strategies developed/described herein can provide a promising approach to unveil the reaction mechanism for other multimetallic electrocatalysts.