Polymorphic phase transformation of Degussa P25 TiO2 by the chelation of diaminopyridine on TiO62− octahedron: Correlation of anatase to rutile phase ratio on the photocatalytic activity

A series of nitrogen-doped Degussa P25 photocatalysts were synthesized successfully by grinding and calcination method using 2,6-diaminopyridine (DAP) as a nitrogen precursor. The prepared samples were characterized by various analytical methods. The phase contents of anatase and rutile in the Degussa P25 powders have been altered by simply changing the proportion of DAP. A mechanism involving chelated DAP molecule on TiO62− octahedron is discussed. The enhanced activity is attributed to synergistic effect in the two phase solid material. Due to the low activation barrier, the effective inter particle electron transfer between the two polymorphs is quite efficient only when they are in close proximity with similar crystallite sizes. The transfer of electrons from the rutile phase to lattice/electron trapping sites of anatase and also to the Ti3+-Vo defect level created by the dopant favors effective charge separation and enhance the photocatalytic activity under solar illumination.

Graphical abstractThe phase contents of anatase and rutile in the Degussa P25 powders have been altered by simply changing the proportion of DAP. A mechanism involving chelated DAP molecule on TiO62− octahedron is discussed. The effective inter particle electron transfer between the two polymorphs is accounted to the close proximity with similar crystallite sizes of the two polymorphsFigure optionsDownload full-size imageDownload high-quality image (121 K)Download as PowerPoint slideHighlights► The contents of anatase and rutile in the Degussa P25 powders have been altered by simply changing the proportion diaminopyridine. ► Efficient photocatalytic property of Degussa P25 under solar irradiation (visible light) is achieved by the incorporation of nitrogen in to Degussa P25 lattice. ► A suitable mechanism is proposed for the chelation of diaminopyridine molecule on TiO62− octahedron to explain the variation of the crystalline phase in the Degussa P25. ► The effective inter particle electron transfer between the two polymorphs is quite possible only they are in close proximity with similar crystallite sizes and the efficiency is accounted to the synergistic effect between two polymorphs.