BaAu2S2: A Au-Based Intrinsic Photocatalyst for High-Performance Visible-Light Photocatalysis

A new Au-based sulfide BaAu 2 S 2 was obtained through solid-state reaction. It crystallizes in the tetragonal space group I 4 1 / amd with unit cell parameters of a = 6.389 72(2) Å, b = 6.389 72(2) Å, c = 12.7872(1) Å, and Z = 4. Its structure features [AuS 2/2 ] ∞ zigzag chains composed of corner-sharing AuS 2 linear units. With a direct band gap of 2.49 eV, BaAu 2 S 2 is suitable for the visible-light harvesting. Moreover, it exhibits excellent visible-light photocatalytic activity, which is 1.3 times that of graphitic carbon nitride (g-C 3 N 4 ) and also demonstrates excellent circulating stability. On the basis of the crystal and electronic structure analysis, the electrons are highly delocalized along the [AuS 2/2 ] chains, and the electron effective mass of BaAu 2 S 2 is only approximately one-fifth of that of g-C 3 N 4, which may help the separation of the electron/hole pairs during the photocatalytic process. Additionally, the absorption coefficient of BaAu 2 S 2 is extremely high, exceeding 1 × 10 4 cm –1 over the entire absorbable visible spectrum ( h ν > E g ), which is significantly higher than that of g-C 3 N 4 . Such factors may contribute to its outstanding photocatalytic performances. According to our best knowledge, BaAu 2 S 2 is the first noble metal-based chalcogenide photocatalyst reported as intrinsic light-harvesting and electron/hole-generating centers. This study may provide valuable insights for further research on photocatalytic materials.