Novel Stannite-type Complex Sulfide Photocatalysts AI2-Zn-AIV-S4 (AI = Cu and Ag; AIV = Sn and Ge) for Hydrogen Evolution under Visible-Light Irradiation

摘要

Photophysical properties and photocatalytic activities for H₂ evolution of the series of stannite-type complex sulfides AI₂-Zn-AIV-S₄ (AI = Cu and Ag; AIV = Sn and Ge) were studied. Diffuse reflection spectra and the plane-wave-based density functional theory (DFT) calculation suggested that the conduction bands were made up of Ge4s4p or Sn5s5p with S3p orbitals, while the valence bands consisted of Cu3d and Ag4d with S3p orbitals. The constituting elements of AI and AIV affected the photophysical and photocatalytic properties. Ru cocatalyst-loaded Cu₂ZnGeS₄, Ag₂ZnGeS₄, and Ag₂ZnSnS₄ showed high activities for photocatalytic H₂ evolution from an aqueous Na₂S+K₂SO₃ solution under visible-light irradiation. Combination of Cu and Ag made it possible that the CuAgZnSnS₄ photocatalyst with a narrow band gap (1.4 eV) utilized a wide range of visible light for the H₂ evolution.