Sodium tantalate photocatalyst was doped with Sr2+ via a solid-state or hydrothermal reaction. Strontium cations doped at B sites in the perovskite-structured lattice via the solid-state reaction induced surface reconstruction of particles, although Na+ at the A site has been expected to be substituted by Sr2+. Recombination of photoexcited electrons and holes was restricted in the photocatalyst doped at the B sites. As a result, the steady-state population of electrons excited by Hg–Xe lamp irradiation increased by 10 times, and the rate of Ag photodeposition increased. Furthermore, A sites were doped with the same cations via the hydrothermal reaction. Surface reconstruction and enhanced electron population were absent in the photocatalyst doped at the A sites. The choice of doping sites was critical to improving the perovskite-structured photocatalyst. Photocatalytic splitting reaction of water is one of the most promising processes for hydrogen fuel production. The photocatalysts La-doped NaTaO3 [1] and Zn-doped Ga2O3 [2] have the highest quantum efficiency for water splitting. Compatible activities have also been achieved by using NaTaO3 doped with alkaline-earth metals, Ca, Sr, and Ba [3]. Hence, doping with heterometals is the key to producing hydrogen fuel. Specific metal elements, despite being impurities in the host lattice, increase the efficiency, but the mechanisms of this increase are still unknown. In this study, we show that Sr2+ cations restricted electron–hole recombination and increased the steady-state population of photoexcited electrons by 10 times when used to dope the B sites of perovskite-structured NaTaO3. The same element failed to restrict recombination when used to dope the A sites. The choice of doping sites was critical to improving the perovskite-structured photocatalyst. References [1] Kudo, A.; Kato, H. Effect of Lanthanide-doping into NaTaO3 Photocatalysts for Efficient Water Splitting. Chem. Phys. Lett. 2000, 331, 373. [2] Sakata, Y.; Matsuda, Y.; Yanagida, T.; Hirata, K.; Imamura, H. ; Teramura, K. Effect of Metal Ion Addition in a Ni Supported Ga2O3 Photocatalyst on the Photocatalytic Overall Splitting of H2O. Catal. Lett. 2008, 125, 22. [3] Iwase, A.; Kato, H.; Kudo, A. The Effect of Alkaline Earth Metal Ion Dopants on Photocatalytic Water Splitting by NaTaO3 Powder. ChemSusChem 2009, 2, 873.

Electron-hole recombination controlled by doping sites in perovskite-structured photocatalysts: Sr-doped NaTaO3

249th National Meeting (2015)

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