A photoactive titanate with a stereochemically active Sn lone pair: Electronic and crystal structure of Sn2TiO4 from computational chemistry

Abstract

TiO 2 remains the most widely studied metal oxide for photocatalytic reactions. The standard approach to reduce the band gap of titania, for increasing the absorption of visible light, is anion modification. For example the formation of an oxynitride compound, where the nitrogen 2p states decrease the binding energy of the valence band. We demonstrate that cation modification can produce a similar effect through the formation of a ternary oxide combining Ti and an ns 2 cation, Sn(II). In Sn 2 TiO 4 , the underlying Ti 3d conduction states remain largely unmodified and an electronic band gap of 2.1 eV (590 nm) is predicted by hybrid density functional theory. Our analysis indicates a strong potential for Sn 2 TiO 4 in visible-light driven photocatalysis, which should prove superior to the alternative (SnO 2) 1x (TiO 2) x solid-solution.

Band alignment in SnS thin-film solar cells: Possible origin of the low conversion efficiency

“…3.2 Å ) Sn-S bonds due to the stereochemically active lone pair. 26 In this lower oxidation state of Sn (i.e., II), the 5s 2 orbitals are formally occupied, with the conduction band formed from the empty 5p band. 26 The interaction of Sn 5s and S 3p results in antibonding states at the top of the va lence band.…”

“…26 In this lower oxidation state of Sn (i.e., II), the 5s 2 orbitals are formally occupied, with the conduction band formed from the empty 5p band. 26 The interaction of Sn 5s and S 3p results in antibonding states at the top of the va lence band. 27 In contrast, the ionisation potentials of CdTe and CuInSe 2 have been reported as 5.7 eV from ultraviolet photoelectron spectroscopy 28 and HSE06 calculations, respectively.…”

Drastic changes of electronic structure and crystal chemistry upon oxidation of SnII2TiO4E2 into SnIV2TiO6: An ab initio study

“…The equilibrium volume of Sn II 2 TiO 4 is larger than experiment and the one obtained from energy optimization; this can be assigned to the use of GGA which overestimates volumes contrary to LDA which underestimates them. Also we note that the volume calculated using GGA based PBEsol XC functional is obtained smaller than experiment [9]. However we mainly aim at establishing trends with the changes incurred by the transformation into Sn (Fig.…”

“…They are usually based on titania modified within the anionic substructure such as by preparing titanium oxy-nitrides [8]. But a modification at the cationic sites may also bring a reduction of the band gap and Sn 2 TiO 4 was considered for such applications thanks to divalent tin [9]. [4] which is a member of the solid solution Sn x Ti 1-x O 2 for x = 0.666 investigated by Hirata [10].…”

Epitaxial growth of tin(II) niobate with a pyrochlore structure

“…In typical n-type oxide semiconductors such as In 2 O 3 , ZnO, and SnO 2 , the relatively deep VBM composed mainly of the O-2p orbitals leading to the difficulty in hole doping. On the other hand, tin(II) oxides, including Sn 2 Nb 2 O 7 , are considered to have shallow VBM due to the hybridization of the O-2p and Sn-5sp orbitals [3,[7][8][9]. Indeed, tin monoxide (SnO), a prototypical tin(II) oxide with such a VBM characteristic [10,11], is known as a p-type semiconductor [12,13].…”