Structure of the water-splitting photocatalyst oxysulfide α-LaOInS2 and ab initio prediction of new polymorphs.

We unveil the structure and investigate the visible light water-splitting of the photocatalyst α-LaOInS2, the second polymorph in this composition. This remarkable oxysulfide exhibits rare mixed anion InS5O octahedra leading to both O-2p and S-3p hybridized with indium states in the vicinity of the Fermi level. Ab initio structure prediction shows the stability of such heteroleptic environments and points to other hypothetical polymorphs.