Photocatalytic water splitting from Koopmans spectral functionals: The case of $TiO_2$ polymorphs

Photocatalytic water splitting has drawn considerable attention for renewable energy production. Since the first reported photocatalytic water splitting by titanium dioxide, this material remains one of the most promising photocatalysts, due to its suitable band gap and band-edge positions. However, estimating both of these properties is a challenging task for standard DFT functionals. Here we show how Koopmans spectral functionals can accurately predict the band structure and level alignment of rutile, anatase and brookite, demonstrating the advantage of these (orbital-density-dependent) spectral functionals for predicting materials’ band structures.