In situ Sn2+-incorporation synthesis of titanate nanotubes for photocatalytic dye degradation under visible light illumination

► Sn2+ ions sensitize titanate nanotubes for photocatalysis under visible-light illumination. ► The Sn 5s orbital replaces the O 2p orbital as the top level of the valence band of titanates. ► The presence of Sn2+ lifts the valence band of titanate nanotubes by approximately 0.9 eV. ► The doped Sn2+ sites are active in donating photo-induced charges to dye degradation.