Probing the electronic structure and hydride occupancy in barium titanium oxyhydride through DFT-assisted solid-state...

Area of Science:

• Materials Science
• Solid-State Chemistry
• Energy Storage Materials

Background:

• Perovskite-type oxhydrides, like barium titanium oxyhydride (BaTiO_3-yH_y), exhibit mixed hydride ion and electron conduction.
• These materials are attractive for energy storage devices, but their electrical conductivity mechanisms and composition-dependent properties are not fully understood.
• Clarifying these aspects is crucial for optimizing their performance in energy storage applications.

Purpose of the Study:

• To elucidate the local hydride environment, electronic structure, and conduction dynamics in barium titanium oxyhydride.
• To investigate the relationship between material composition and electrical conductivity.
• To establish a reliable method for differentiating between feasible electronic structures in these complex solids.

Main Methods:

• Density Functional Theory (DFT)-assisted solid-state Nuclear Magnetic Resonance (NMR) spectroscopy.
• Analysis of hydride local environment and electronic structure.
• Investigation of hydride conduction dynamics across varying hydrogen concentrations and temperatures.

Main Results:

• DFT-assisted solid-state NMR effectively differentiates between various possible electronic structures in barium titanium oxyhydrides.
• Reduction of BaTiO₃ leads to delocalized electrons forming a bandstate across all titanium atoms.
• Vacated anion sites are occupied by at most one hydride ion or remain vacant, a stable structure across 0.13 ≤ y ≤ 0.31 and 100–300 K.

Conclusions:

• The electronic structure of barium titanium oxyhydrides is characterized by a single occupied bandstate, independent of hydrogen concentration and temperature within the studied ranges.
• Solid-state NMR, guided by DFT, is a powerful tool for characterizing the electronic and structural properties of oxhydrides.
• These findings provide fundamental insights into the conductivity mechanisms, paving the way for the rational design of advanced energy storage materials.