In Situ Synchrotron Powder Diffraction Study of Cd Intercalation into Chevrel Phases: Crystal Structure and Kinetic...

Chevrel phases are molybdenum chalcogenides of formula M _xMo₆X₈ (where M is a cation and X is a chalcogen) that present a complex and captivating intercalation chemistry that has drawn the interest of the solid-state chemistry community since their discovery. This property has a huge potential for applied science and device development for energy storage and pollutant removal and detection, but a deeper knowledge of the intercalation processes and chemistry is still necessary. In the present work, the intercalation of Cd²⁺ in aqueous solution has been studied, taking advantage of the complementarity of electrochemical characterization and synchrotron powder diffraction acquired during an in situ combined experiment. During the experiment, industrially adequate electrochemical conditions (room temperature and reduced process time) were applied, allowing a better understanding of the intercalation processes. The intercalated phases obtained by electrochemistry have been characterized ex situ, and for the first time the structures of Cd₂Mo₆X₈ (X = S, Se) have been determined. Unexpectedly, Cd₂Mo₆Se₈ presents a trigonal crystal structure with only cavity 2 occupied, which has not been encountered before for Chevrel phases.