The Fe4+/3+ Redox Mechanism in NaFeO2: A Simultaneous Operando Nuclear Resonance and X-ray Scattering Study

Abstract

Simultaneous operando Nuclear Forward Scattering and transmission X-ray diffraction and 57Fe Mössbauer spectroscopy measurements were carried out in order to investigate the electrochemical mechanism of NaFeO2 vs. Na metal using a specifically designed in situ cell. The obtained data were analysed using an alternative and innovative data analysis approach based on chemometric tools such as Principal Component Analysis (PCA) and Multivariate Curve Resolution - Alternating Least Squares (MCR-ALS). This approach, which allows the unbiased extraction of all possible information from the operando data, enabled the stepwise reconstruction of the independent “real” components permitting the description of the desodiation mechanism of NaFeO2. This wealth of information allows a clear description of the electrochemical reaction at the redox-active iron centres, and thus an improved comprehension of the cycling mechanisms of this material vs. sodium.