A Novel Series of the New Visible-Light-Driven Photocatalysts MCo_1/3Nb_2/3O₃ (M = Ca, Sr, and Ba) with Special Electronic Structures

Abstract

A new series of ABO3-type perovskite photocatalysts MCo1/3Nb2/3O3 (M = Ca, Sr, and Ba) were synthesized by a solid-state reaction method, in which the B site is occupied by Co2+ and Nb5+ randomly in a charge-balanced manner. They were characterized by powder X-ray diffraction, UV−vis diffuse reflectance spectroscopy and photocatalytic activity measurements with Pt and NiO x cocatalyst under visible-light irradiation (λ > 420 nm), respectively. It is determined from the reflectance spectra that the optical transitions for these compounds, corresponding to visible-light absorption, are directly forbidden, and the band structures are suggested to be composed of the Co2+ 3d states and the Nb5+ 4d states. The feature of the electronic structure for BaCo1/3Nb2/3O3 calculated by the full potential-linearized augmented plane wave (F-LAPW) method shows that the O 2p states are strongly hybridized with the Co2+ 3d states, and little hybridized with the Nb5+ 4d states. The difference in their photocatalytic activity is ascribed to their special crystal and electronic structures.

Tuning the electronic structure of SrTiO3/SrFeO3−x superlattices via composition and vacancy control

“…4 Additionally, the relatively wide optical band gap of SrTiO 3 (3.2 eV) limits its ability to absorb light in the solar spectrum. Past work has explored a variety of routes to tune the band gap and edges of SrTiO 3 , including chemical doping and substitution, [5][6][7][8][9][10][11] epitaxial strain, 12 and quantum confinement. 13 Layered oxide thin films, usually grown by molecular beam epitaxy 14 or pulsed laser deposition, 15 can tune electronic structure via quantum confinement and geometric distortions not found in the bulk components.…”

Photocatalytic Splitting of Water Over a Novel Visible-Light-Response Photocatalyst Nd2InTaO7

“…It was interesting to notice oxygen evolution was not observed from pure water in this experiment. It may be related to the physisorbed and chemisorbed states of O 2 molecules on the surface of the photocatalyst particles, just as found on TiO 2 [30], Bi 2 InNbO 7 [31], BaCo 2/3 Nb 4/3 O 3 [9]. On the one hand, it was proposed that there were both physisorbed and chemisorbed O 2 molecules on the surface of TiO 2 through low-energy photon irradiation, where the physisorbed O 2 was produced through the neutralization of chemisorbed O 2 -species by photogenerated holes [30].…”

“…Because the visible light accounts for 43% of the whole solar energy, the development of visible-light-response photocatalysts will be valuable from the viewpoint of a potentially efficient utilization of solar energy. Some visible-light-response photocatalysts such as nitrogen-doped TiO 2 [3] and new materials [2,[6][7][8][9][10] have been developed for water splitting. However, a visible-light-sensitive photocatalyst with high activity is still desirable.…”

DEGRADATION OF METHYLENE BLUE UNDER SOLAR LIGHT USING QUARTZ – Bi2WO6 NANOCOMPOSITES

“…The longer wavelength exhibited indicates that they can easily absorb visible light, which is advantages to their visible-light photocatalytic activity. For a crystalline semiconductor, it is known that the optical absorption near the band edge follows the equation [39][40][41].…”