Tunable band gap of N-V co-doped Ca:TiO2-B (CaTi5O11) for visible-light photocatalysis

Visible-light photocatalysis in layered perovskite CaTi5O11 is measured by band-gap tuning with co-doped anionic nitrogen (N) and cationic vanadium (V). The screening of hybrid density functional (HSE06) calculation reveals that strong Coulomb interaction between the dopants and other atoms makes N-V co-doping energetically favorable and effective for narrowing the band gap. More importantly, co-doping can eliminate the impurity states to reduce the electron-hole combination and improve the efficiencies of photocatalysis, since the mono-doped N or V ion produces impurity near the Fermi level. The impurity state captures the photoexcitation-generated carriers and accelerates the recombination process of the electron-hole pairs, thus suppressing their photocatalytic performance. The alignment of the band edge position with respect to the water oxidation/reduction potential indicates that N-V co-doped CaTi5O11 can act as a potential photocatalytic water catalyst. Co-doping is expected to be an effective way of improving the visible-light photocatalytic activity in layered perovskite due to the elimination of recombining the electron-hole pairs. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.