Negative Knight Shift in Ba-Ti Oxyhydride: An Indication of the Multiple Hydrogen Occupation

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Multiple hydrogen occupation in Ba-Ti oxyhydride is demonstrated by a negative Knight shift in the 1H magic-angle spinning (MAS) NMR spectra combined with hydrogen concentration and X-ray photoelectron spectroscopic analysis. A negative Knight shift, an indicator of the interaction between conduction band electrons and a probe nucleus, is observed in the 1H MAS NMR signal of Ba-Ti oxyhydrides at room temperature for the first time. This Knight shift indicates multiple hydrogen occupation. This was confirmed by the X-ray photoelectron spectra of Ba-Ti oxyhydrides and the hydrogen concentrations. The presence of hydrogen species with different bonding characteristics indicates a flexible hydrogen configuration in Ba-Ti oxyhydrides, from an ionic-state hydride ion with single occupation to partially anionic state hydrogen atoms with multiple occupation. It also indicates the potential to modify the electronic structure and physical properties of Ba-Ti oxyhydrides by manipulating their hydrogen configuration.

Original languageEnglish
Pages (from-to)7178-7185
Number of pages8
JournalChemistry of Materials
Issue number18
Publication statusPublished - 2019 Sept 24


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