Abstract
The characteristic properties of TiO2 (anatase) make doping necessary to enhance its photocatalytic activity. Herein, a density functional theory (DFT) study using the Heyd–Scuseria–Ernzerhof (HSE) hybrid functional was performed to precisely investigate the effect of mono- and co-doping (Ni, Se and B) on the structural, electronic and optical properties of anatase TiO2. Notably, the origin of the enhanced photocatalytic activity of the modified systems was determined. The response to visible light was enhanced for all the mono- and co-doped materials except for Bint, and the highest absorption coefficient was observed for Se4+ mono-doping and Se/Bint+sub and Ni/Bsub co-doping. The decrease in bandgap is associated with a red shift in the absorption edges with the smallest bandgap calculated for Ni/Bsub (2.49 eV). Additionally, the Ni, Se4+ and Se2− mono-doped systems and Ni/Se4+ co-doped systems are proposed as promising photocatalysts for water splitting applications and further experimental validation. Moreover, the Ni/Bint+sub and Se/Bint+sub co-doped materials can also be valuable photocatalysts for other energy applications due to their enhanced visible light activity and the prolonged lifetime of their produced charge carriers.
Highlights
IntroductionNickel doping was largely exhibited since the ionic radius of Ni2+ ions is slightly higher than that of Ti4+ ions.[9]
In recent years, clean energy technology has attracted great interest for a sustainable economy and reduction of environmental pollution.[1,2] photocatalytic materials have been extensively investigated, especially semiconductor photocatalysts
The positions of edges of the valence and conduction bands were detected from the DOS analysis depending on their relative positions compared to pure anatase TiO2.10 The calculations for pure anatase TiO2 shows that the VBE is located at 2.94 eV, while the CBE position is 0.32 eV more negative than the reduction potential of H+/H2, which agrees with the previous experimental values.[51]
Summary
Nickel doping was largely exhibited since the ionic radius of Ni2+ ions is slightly higher than that of Ti4+ ions.[9]. Cationic Se4+ and Se0 have been signi cantly assigned experimentally, Se2À was only clari ed theoretically in the previous work by Harb.[10] Xie et al attributed the narrowed gap (2.19 eV) and the suppressed electron/hole recombination rate upon Se4+ doping to the energy states appearing in the gap region upon the incorporation of Se.[11] A DFT-based study with HSE level showed the effect of Se doping at different valence states with different concentrations on water splitting.[10] The results showed that substitutional cationic and anionic Se can induce the best band positions for the water splitting reaction. The photocatalytic reaction of TiO2-based materials was investigated by determining the band edge position of modi ed materials with respect to the normal hydrogen electrode (NHE) potential for water splitting
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