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

• Published in: International journal of hydrogen energy 2018-01, Vol.43 (4), p.2073-2082
• Main Authors: Mandari, Kotesh Kumar, Police, Anil Kumar Reddy, Do, Jeong Yeon, Kang, Misook, Byon, Chan
• Format: Article
• Language: English
• Subjects: Nitrogen doped titania; Photocatalytic water splitting; Rare-earth metal doped TiO2; Solar to hydrogen production
• ISSN: 0360-3199; 1879-3487
• DOI: 10.1016/j.ijhydene.2017.12.050

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 OTiN and GdOTi 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 H2 production from water splitting. The 2 wt% gadolinium and nitrogen co-doped TiO2 has shown 10764 μmol g−1 H2 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. Schematic representation of excitations in N-doped TiO2, Gd-doped TiO2 and Gd, N co-doped TiO2. [Display omitted]