Nakamura Takashi, Oike Ryo, Kimura Yuta, Tamenori Yusuke, Kawada Tatsuya, Amezawa Koji
Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, 980-8577, Japan.
Japan Synchrotron Radiation Institute, 1-1-1, Kouto, Sayo-cho, Sayo-gun, Hyogo, 679-5198, Japan.
ChemSusChem. 2017 May 9;10(9):2008-2014. doi: 10.1002/cssc.201700237. Epub 2017 Apr 13.
An operando soft X-ray absorption spectroscopic technique, which enabled the analysis of the electronic structures of the electrode materials at elevated temperature in a controlled atmosphere and electrochemical polarization, was established and its availability was demonstrated by investigating the electronic structural changes of an La NiO dense-film electrode during an electrochemical oxygen reduction reaction. Clear O K-edge and Ni L-edge X-ray absorption spectra could be obtained below 773 K under an atmospheric pressure of 100 ppm O /He, 0.1 % O /He, and 1 % O /He gas mixtures. Considerable spectral changes were observed in the O K-edge X-ray absorption spectra upon changing the PO2 and application of electrical potential, whereas only small spectral changes were observed in Ni L-edge X-ray absorption spectra. A pre-edge peak of the O K-edge X-ray absorption spectra, which reflects the unoccupied partial density of states of Ni 3d-O 2p hybridization, increased or decreased with cathodic or anodic polarization, respectively. The electronic structural changes of the outermost orbital of the electrode material due to electrochemical polarization were successfully confirmed by the operando X-ray absorption spectroscopic technique developed in this study.
建立了一种原位软X射线吸收光谱技术，该技术能够在可控气氛和电化学极化条件下对高温下电极材料的电子结构进行分析，并通过研究La NiO致密膜电极在电化学氧还原反应过程中的电子结构变化来证明其有效性。在100 ppm O₂/He、0.1% O₂/He和1% O₂/He气体混合物的大气压下，在773 K以下可以获得清晰的O K边和Ni L边X射线吸收光谱。改变PO₂和施加电势时，在O K边X射线吸收光谱中观察到相当大的光谱变化，而在Ni L边X射线吸收光谱中仅观察到小的光谱变化。O K边X射线吸收光谱的一个预边峰反映了Ni 3d - O 2p杂化的未占据态密度，分别随着阴极或阳极极化而增加或减少。通过本研究开发的原位X射线吸收光谱技术成功证实了由于电化学极化导致的电极材料最外层轨道的电子结构变化。
