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 [AuS_2/2]_∞ 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 [AuS_2/2] 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 > E_g), 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.