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-C 3 N 4 ) for the enhanced photocatalytic activity of water spilitting into hydrogen generation. In order to prepare Ag/g-C 3 N 4 and Pt/g-C 3 N 4 , initial adsorption of noble metal ions was performed on the g-C 3 N 4 surface, followed by reducing them by using NaBH 4 . Decoration of Ag or Pt nanoparticles on g-C 3 N 4 can extend the visible light adsorption and promote segregation of the photogenerated carriers, which contribute to an improved photocatalytic performance. Pt/g-C 3 N 4 has a higher photocatalytic activity in water spilitting for H 2 generation (841 μmol g -1 h -1 ) than that of Ag/g-C 3 N 4 (305 μmol g -1 h -1 ), however, almost no H 2 generation for pure g-C 3 N 4 . 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-cata- lyst than Ag can, due to the d-centre of Pt is closer to Fermi level than that of Ag on the g-C 3 N 4 surface, which can promote the charge separation and accelerate the electron transformation.