Photophysical and Photocatalytic Properties of Ag ₂ M ₂ O ₇ (M=Mo, W)

Abstract

Ag‐based oxides, Ag 2 M 2 O 7 (M=Mo, W) with a triclinic structure, were prepared using a conventional solid‐state reaction method, and their band structures and photocatalytic properties were investigated. From the electronic band structure calculations, Ag 2 Mo 2 O 7 had an indirect band gap of 2.65 eV, whereas Ag 2 W 2 O 7 had a direct band gap of 3.18 eV. Moreover, the calculated electron affinities were 4.75 eV for Ag 2 Mo 2 O 7 and 4.62 eV for Ag 2 W 2 O 7 . The smaller band gap and higher electron affinity of Ag 2 Mo 2 O 7 than those of Ag 2 W 2 O 7 originated from the contribution of the unoccupied Mo 4 d orbital to the conduction band, which was positioned at a lower energy level than the W 5 d orbital. The effects of the different band structure characteristics in Ag 2 M 2 O 7 (M=Mo, W) on the photocatalytic activity were investigated by the degradation of a Rhodamine B dye solution under visible light irradiation. The results showed that the photocatalytic activity of Ag 2 Mo 2 O 7 was much higher than that of Ag 2 W 2 O 7 and comparable with a well‐known WO 3 powder. The higher photocatalytic property of Ag 2 Mo 2 O 7 was attributed to its higher optical absorption ability and lower charge recombination rate.