Synthesis, structure, and intercalation chemistry of tungsten oxyhalides

Tungsten oxyhalides are a unique class of mixed anionic materials that have been lightly studied over the years. There have been multiple structures proposed for both the chloride and iodide and little information beyond these structure papers has been reported. We have synthesized each of the two-dimensional (2D) analogs of the WO2X2 structure where X = Cl, Br, and I. This series of compounds are structurally very similar, but each possess unique differences based on the size of the halide. The basis for these structures is 2D tungsten oxide sheets separated by a van der Waals gap with halide termination. The halides frequently dictate the symmetry of the crystal structure and give rise to several interesting properties. In addition, the synthesis process appears to give rise to several polymorphs implying that there are very small differences in energy between these structures. Finally, we studied the intercalation chemistry of each of the tungsten oxyhalides with alkali and transition metals to better understand the processes governing the intercalation process. The properties of both the base materials and intercalated compounds will be discussed along with potential applications for this fascinating set of materials.