Phosphorus and nitrogen co-doped titania photocatalysts with a hierarchical meso-/macroporous structure

Visible light-active phosphorus and nitrogen co-doped meso-/macroporous titania materials were prepared by a simple two-step approach of the direct phosphation with the use of phosphoric acid solution and the succedent nitridation with the use of the urea solution. The prepared materials were characterized by UV–vis, solid-state 31P MAS NMR, FT-IR, XPS, XRD, SEM, TEM, and N2 adsorption analysis. Direct synthesis of phosphorus-doped meso-/macroporous titania materials could inhibit the formation of brookite phase and increase the surface area significantly, resulting in the hierarchical porous framework of nanocrystalline anatase phase with enhanced thermal stability and large porosity, and these features retained during the subsequent nitridation. The incorporation of P and N in the anatase titania lattice in the form of O–Ti–N, O–P–N, and Ti–O–P linkages was evidenced, and the extension of the absorption edges into the visible region and the corresponding narrowing of band gaps were observed in these N and P co-doped meso-/macroporous titanias, giving a higher photocatalytic activity in the degradation of Rhodamine B dye under visible-light irradiation than the samples doped with only N or P. The beneficial effect of hierarchical meso-/macroporous structure is also examined.