Comparison of pt and Ag as co-catalyst on g-C₃N₄ for improving photocatalytic activity: Experimental and DFT studies

In this work, Ag and Pt were compared as a co-catalyst on graphitic carbon nitride (g-C₃ N₄ ) for the enhanced photocatalytic activity of water spilitting into hydrogen generation. In order to prepare Ag/g-C₃ N₄ and Pt/g-C₃ N₄, initial adsorption of noble metal ions was performed on the g-C₃ N₄ surface, followed by reducing them by using NaBH₄. Decoration of Ag or Pt nanoparticles on g-C₃ N₄ can extend the visible light adsorption and promote segregation of the photogenerated carriers, which contribute to an improved photocatalytic performance. Pt/g-C₃ N₄ has a higher photocatalytic activity in water spilitting for H₂ generation (841 μmol g⁻¹ h⁻¹) than that of Ag/g-C₃ N₄ (305 μmol g⁻¹ h⁻¹), however, almost no H₂ generation for pure g-C₃ N₄. For checking the photogenerated holes,^·OH generation rate was tested by using the reaction of terephthalic acid (TA) with^·OH to form 2-hydroxy-terephthalic acid (TAOH). On the basis of experimental results and theoretical calculation, a possible photocatalytic mechanism is put forward. It is suggested that Pt can play a better role as the co-catalyst than Ag can, due to the d-centre of Pt is closer to Fermi level than that of Ag on the g-C₃ N₄ surface, which can promote the charge separation and accelerate the electron transformation.