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

A new Au-based sulfide BaAu2S2 was obtained through solid-state reaction. It crystallizes in the tetragonal space group I41/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 [AuS2/2]∞ zigzag chains composed of corner-sharing AuS2 linear units. With a direct band gap of 2.49 eV, BaAu2S2 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-C3N4) and also demonstrates excellent circulating stability. On the basis of the crystal and electronic structure analysis, the electrons are highly delocalized along the [AuS2/2] chains, and the electron effective mass of BaAu2S2 is only approximately one-fifth of that of g-C3N4, which may help the separation of the electron/hole pairs during the photocatalytic process. Additionally, the absorption coefficient of BaAu2S2 is extremely high, exceeding 1 × 104 cm-1 over the entire absorbable visible spectrum (hν > Eg), which is significantly higher than that of g-C3N4. Such factors may contribute to its outstanding photocatalytic performances. According to our best knowledge, BaAu2S2 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.