Rare earth metal Gd influenced defect sites in N doped TiO2: Defect mediated improved charge transfer for enhanced photocatalytic hydrogen production

Abstract

In this experimental studies, we report the synthesis of TiO2 co-doped by both cationic and anionic sites by simple sol-gel based method. All the prepared samples exhibit the anatase crystalline morphology however, showed lattice distortion caused by the displacement of Ti4+ sites by Gd3+. The improved visible absorption is witnessed by the Gd and N co-doping with an assured redshift in the absorption edge. The N and Gd displacement inside TiO2 lattice accompanied by the creation of O-Ti-N and Gd-O-Ti bonds are characterized by the X-ray photoelectron spectra. The strong resonance signal by Gd4f electrons in the electron paramagnetic resonance spectroscopy further substantiate the displacement of lattice cites of TiO2 by Gd3+ ions. The longevity of the photo produced charges observed in fluorescence spectra of Gd and N co-doped TiO2 is because of the effective transfer of charges to the defect sites. The aforementioned catalysts are tested for their capacity for the H-2 production from water splitting. The 2 wt% gadolinium and nitrogen co-doped TiO2 has shown 10764 mu mol g(-1) H-2 production which is 26 times higher than the commercial Degussa P-25 catalyst. The enhanced activity for hydrogen production can be attributed to factors such as increased absorptivity under visible light and effective charge carrier separation.