XPS and IR spectral studies on the structure of phosphate and sulphate modified titania – A combined DFT and experimental study

The structures of phosphated titania and sulphated titania are studied with a combined approach using DFT/B3LYP/Lanl2DZ and experimental studies such as XRD, XPS, and DRIFT spectra. The infrared absorptions, Mulliken charges, bond lengths, and dipole moments are investigated for the phosphated and sulphated titania structures optimized by DFT calculations. The XRD patterns obtained for both the modified titania show that the as-synthesized materials are amorphous in nature. The DRIFT spectra show the presence of bidentate complex in both sulphated and phosphated titania. The XPS data show the presence of Ti-O-S and Ti-O-P linkages in sulphated and phosphated titania respectively. The evaluation of IR absorptions obtained by DFT and DRIFT spectra reveal the most favorable structure of bridged bidentate for sulphated titania and a combination of monodentate and chelating bidentate for phosphated titania.