Goubard-Bretesché Nicolas, Crosnier Olivier, Douard Camille, Iadecola Antonella, Retoux Richard, Payen Christophe, Doublet Marie-Liesse, Kisu Kazuaki, Iwama Etsuro, Naoi Katsuhiko, Favier Frédéric, Brousse Thierry
Institut des Matériaux Jean Rouxel (IMN), CNRS UMR 6502 - Université de Nantes, Nantes, 44322 Cedex 3, France.
Réseau sur le Stockage Electrochimique de l'Energie, CNRS FR 3459, Amiens, 80039 Cedex, France.
Small. 2020 Aug;16(33):e2002855. doi: 10.1002/smll.202002855. Epub 2020 Jul 12.
In nanosized FeWO electrode material, both Fe and W metal cations are suspected to be involved in the fast and reversible Faradaic surface reactions giving rise to its pseudocapacitive signature. In order to fully understand the charge storage mechanism, a deeper insight into the involvement of the electroactive cations still has to be provided. The present paper illustrates how operando X-ray absorption spectroscopy is successfully used to collect data of unprecedented quality allowing to elucidate the complex electrochemical behavior of this multicationic pseudocapacitive material. Moreover, these in-depth experiments are obtained in real time upon cycling the electrode, which allows investigating the reactions occurring in the material within a realistic timescale, which is compatible with electrochemical capacitors practical operation. Both Fe K-edge and W L -edge measurements point out the involvement of the Fe /Fe redox couple in the charge storage while W acts as a spectator cation. The result of this study enables to unambiguously discriminate between the Faradaic and capacitive behavior of FeWO . Beside these valuable insights toward the full description of the charge storage mechanism in FeWO , this paper demonstrates the potential of operando X-ray absorption spectroscopy to enable a better material engineering for new high capacitance pseudocapacitive materials.
在纳米级FeWO电极材料中，铁（Fe）和钨（W）金属阳离子都被怀疑参与了快速且可逆的法拉第表面反应，从而产生其赝电容特性。为了全面理解电荷存储机制，仍需更深入地了解电活性阳离子的参与情况。本文阐述了如何成功运用原位X射线吸收光谱法收集到前所未有的高质量数据，从而阐明这种多阳离子赝电容材料复杂的电化学行为。此外，这些深入实验是在电极循环过程中实时获得的，这使得能够在与电化学电容器实际运行相兼容的实际时间尺度内研究材料中发生的反应。铁K边和钨L边测量均表明Fe/Fe氧化还原对参与了电荷存储，而钨作为旁观阳离子。这项研究的结果能够明确区分FeWO的法拉第行为和电容行为。除了这些对全面描述FeWO电荷存储机制有价值的见解外，本文还展示了原位X射线吸收光谱法在为新型高电容赝电容材料实现更好的材料工程方面的潜力。
