Strong hybridization between Bi-6s and O-2p orbitals in Sillén–Aurivillius perovskite Bi ₄ MO ₈ X (M = Nb, Ta; X = Cl, Br), visible light photocatalysts enabling stable water oxidation

Oxyhalides Bi ₄ MO ₈ X are revealed to function as stable O ₂ -evolving photocatalysts under visible light without suffering from self-oxidative deactivation due to the unique valence band structure.