jp7b05734_si_001.pdf (1.12 MB)
Electronic and Optical Properties of TiO2 Solid-Solution Nanosheets for Bandgap Engineering: A Hybrid Functional Study
journal contribution
posted on 2017-08-04, 00:00 authored by Yanyu Liu, Wei Zhou, Naoto UmezawaHerein,
the electronic and optical properties of TiO2(010) nanosheet
solid solutions with transition metal oxycarbides, nitrides, and oxynitrides,
(TiO2)2/3(M2O3C)1/3 (M = Nb or Ta), (TiO2)2/3(MN2)1/3 (M = W or Mo), and (TiO2)2/3(MOE)1/3 (M = W, Mo, E = C, and M = Nb, Ta, E = N) are systematically
investigated. Forming a solid solution is a viable way to realize
visible-light absorption and a direct band gap. The electron affinity
of a solid-solution nanosheet closely depends on the energy level
of the transition metal (M) d states; i.e., the hybridization of the
M d states and Ti–O antibonding states introduces new bonding
states, leading to a downward shift of the conduction band minimum.
Meanwhile, the ionization potentials of these solid solutions are
relatively low because of the introduction of high-lying occupied
C/N 2p states, which lift the valence band maximum upward above that
of the pristine TiO2. The modulation of band edges effectively
narrows the band gaps of the solid solutions, except for transition
metal oxynitrides. Among the examined solid solutions, (TiO2)2/3(WOC)1/3 was the most promising nanosheet
for water splitting owing to its suitable band edges and responsive
to visible and ultraviolet light.