Photophysical and photocatalytic properties of ANbO3 (A=Na, K) photocatalysts

Alkali niobates ANbO3 (A=Na, K) photocatalysts were prepared by a conventional solid state reaction method. The samples were characterized by X-ray diffraction, UV–vis diffuse reflectance spectroscopy, N2 adsorption–desorption measurement, and scanning electron microscopy. It was found that ANbO3 (A=Na, K) are indirect band-gap semiconductors with an orthorhombic system. The band structures and density of states (DOS) were theoretically calculated by the density functional theory. The photocatalytic activities were evaluated by photoreduction of CO2 into CH4. It was observed that KNbO3 showed a higher photocatalytic activity than NaNbO3 due to the narrower band gap and higher mobile charge carriers, which are helpful to enhance the light absorption and promote photoinduced carriers transport in the photocatalysts so as to improve the photocatalytic performance.

► The photocatalytic reduction of CO2 over KNbO3 was first investigated in this paper. ► The rate of CH4 generation of KNbO3 was as high as 7.0 ppm/h in contrast to that of NaNbO3 (2.3 ppm/h). ► It is ascribed to KNbO3 having narrower band gap and higher mobile charge carriers. ► These are helpful to the light absorption and photoinduced carriers transposition.