ABSTRACT
The p-block metal oxides that involve typical metal ions (In3+, Ga3+, Ge4+, Sn4+, and Sb5+) with d10 electronic configuration have been demonstrated to make a stable photocatalyst for the overall splitting of water to produce H2 and O2 when combined with RuO2 as a promoter. The influences of preparation methods,
“DK3029_C020” — #2
calcination temperature, the amount of RuO2 dispersed, and the states of RuO2 particles on the activity of RuO2-dispersed p-block metal oxides showed that crystallization of p-block metal oxides and high dispersion of RuO2 particles on them led to high photocatalytic performance: H2 and O2 were stably produced as the stoichiometric ratio under UV irradiation. Alkaline metal and alkaline earth metal oxides consisting of distortedMO6 octahedra andMO4 tetrahedra (M=metal ion) with dipole moment were photocatalytically active, whereas the metal oxides with distortion-free units exhibited negligible activity. Amechanism has been proposed that internal fields due to the dipole moment, promote the charge separation upon photoexcitation. For the electronic structures, density function theory (DFT) calculation showed that the p-block metal oxides with d10 configuration had the valence bands ofO2p orbitals and the conduction band of hybridized sp orbitals. The nature of the conduction bands was different from that of conventional transition metal oxides involving metal ions (Ti4+, Zr4+, Nb5+, and Ta5+) with d0 configuration. The broad hybridized s and p orbitals have large band dispersions which are able to produce photoexcited electrons with large mobility. This is useful for the transfer of photoexcited electrons without recombination to fine RuO2 particles dispersed on the surface as a promoter. The p-block metal oxide group with d10 configuration is concluded to form a new series of the photocatalysts different from the conventional transition metal oxides with d0 configuration.
