  Photocatalytic water splitting is a promising strategy for large-scale clean
energy production. However, efficient and low-cost solid-state photocatalysts
are still lacking. We present here first-principles calculations to investigate
the suitability as photocathode of an epitaxial layer of strontium germanate on
a Si(100) single crystal. Conduction and valence bands offsets at the interface
between these two semiconductors were determined using state-of-the-art
approximations of density functional theory for the accurate prediction of band
alignments. The resulting type-III band line-up is also confirmed by inspection
of the spatially resolved density of states. It is concluded that the
electronic structure of the investigated heterostructure is favorable for
photocathodic functionality.
