d¹⁰ or d⁰? Theoretical and experimental comparison between rutile GeO₂ and TiO₂ for photocatalytic water splitting

Abstract

A comprehensive comparison between rutile-TiO2 and GeO2 proves that the d10 metal in octahedral coordination leads to a high charge mobility.

First-Principles Calculations on Narrow-Band Gap d10 Metal Oxides for Photocatalytic H2 Production: Role of Unusual In2+ Cations in Band Engineering

“…Generally, the effective masses of electrons and holes are inversely proportional to their migration rates, which is closely related to the photocatalytic activity. Benefiting from the strong band edge dispersion of the CB, the m e * of PtIn 6 (Ga/InO 4 ) 2 (0.145 m 0 and 0.140 m 0 ) and PtIn 6 (GeO 4 ) 2 O (0.160 m 0 ) is relatively smaller than that of some famous photocatalysts, such as rutile TiO 2 (0.561 m 0 ), SrTiO 3 (0.39 m 0 ), and corundum Ga 2 O 3 (0.22 m 0 ). − For the hydrogen reduction half reaction, light electrons mean a high migration rate, and more electrons could participate in the water reduction reaction. , Meanwhile, the flat nature of the VB, originating from the occupied 5s orbitals In 2+ , indicates that the hole masses are rather heavy. The large ratio of m h */ m e * may provide the effective carrier separation in bulk. , These features exhibit the potential advantage as efficient photocatalysts for H 2 generation from water splitting .…”

New pentlandite-like oxide semiconductors IrIn6XYO8 (X = Ga, In; Y = Ge, Sn, Ti) as potential candidates for photocatalytic water splitting under visible-light irradiation

“…Nonetheless, they are all smaller than some famous photocatalysts, such as rutile TiO 2 (0.561 m 0 ) and SrTiO 3 (0.39 m 0 ). 19 Meanwhile, the flat nature of the VB demonstrates that the hole masses are rather heavy. Although a significant portion of photo-induced electrons and holes still undergo recombination in the bulk, the large ratio of would prolong the lifetime of charge carriers.…”

“…The localized d orbitals lead to a highly narrowed band edge feature in CBM, which is unfavorable for the mobility of photogenerated electrons. 19 For other d 10 metal oxides, there are various kinds of indates [MIn 2 O 4 (M = Ca, Sr), AInO 2 (A = Li, Na)], 20,21 germanate (Zn 2 GeO 4 ), 22 germanium dioxide (GeO 2 ), 19 gallium oxide and gallates [Ga 2 O 3 , ZnGa 2 O 4 , AGaO 2 (A = Ag, Cu)], [23][24][25] stannates [M 2 SnO 4 (M = Ca, Sr)] and antimonates [MSb 2 O 6 (M = Ca, Sr, Ba)]. 26,27 They possess metal cations with the (n À 1)d 10 ns 0 electronic configuration, which displays strong band edge dispersion in the CBM.…”

Combined Analyses on Electronic Structure and Molecular Orbitals of d10 Bimetal Oxide In2Ge2O7 and Photocatalytic Performances for Overall Water Splitting and CO2 Reduction

“…This ratio (10.311) is comparable with that in rutile GeO 2 (1.597/0.192 along the [001] direction). 44 As shown in Figure 3, the VBM is contributed mainly by the O 2p orbitals, In 4d orbitals, and Ge 3d orbitals, while the CBM is mainly composed of In 5s, Ge 4s, and O 2s orbitals. The obvious tailing in energy of the CBM is due to the delocalized characteristic of Ge and In s-orbitals, in good agreement with the above band structure analyses.…”