In Situ Spectroscopic Identification and DFT-Assisted Prediction of the Valence and Structure of Tungsten Ions in a Cationic/Anionic Molten Salt System

Understanding the reduction mechanism and coordination of tungsten ions in molten salt is one of the key factors to improve the electrolysis efficiency of tungsten carbide. In situ spectroscopy combined with simulation calculation is a strong analytical technique for characterizing chemical species and their behaviors in molten salts. The tungsten ion group was investigated by in situ high-temperature and room-temperature spectroscopy combined with density functional theory (DFT) calculations. For the described in situ spectroscopic studies, a new setup was used, which allowed the registration of UV–vis spectra of tungsten ions in cationic and anionic molten salt systems. The DFT calculation results proved useful for estimating the trend of experimental spectra. Through experimental and theoretical studies, the tungsten ion groups in various molten salt systems were identified, and the effect of cations and anions in molten salt systems onto tungsten ion group formation could be elucidated.