New X-Ray Spectroscopy Techniques for Energy Materials Research

X-ray Absorption Spectroscopy (XAS) is an established experimental technique that is used for the study of the electronic and local atomic structure of materials. The high sensitivity of the method together with its element selectivity make it very suitable for the study of energy materials. The technique is also frequently used for the study of processes in situ and under operando conditions.<br/>In recent years, advanced spectroscopy techniques and analysis methods have been used to circunvent some of the shortcomings of traditional XAS. For example, X-ray Emission Spectroscopy at the Kb emission line can be used to perform spin-selective spectroscopy. In addition, the use of Modulation Excitation assisted by phase-sensitive detection (ME-PSD) analysis methods can significantly enhance the sensitivity of XAS by filtering out contributions of spectator species that are unaltered by the external stimulation.<br/>In this contribution I will present two recent examples ilustrating the application of these new methodologies to the study of electrochochemical systems and energy materials. The changes in the structure of the iron metal centre in prussian blue and prussian blue analogues have been studied as a function of the applied potential, and the changes have been assigned to the iron in low and high spin. ME-PSD analysis has been applied to the study of the reversible ferrocyanide/ferricyanide couple using XAS.