Ag2S/g-C3N4 composite photocatalysts for efficient Pt-free hydrogen production. The co-catalyst function of Ag/Ag2S formed by simultaneous photodeposition

Abstract

Without Pt as cocatalyst, the photocatalytic hydrogen evolution activity of graphitic carbon nitride (g-C₃N₄) or even its composite is normally rather low (<1 μmol h⁻¹). Exploring Pt-free cocatalysts to substitute precious Pt is of great importance in the photocatalytic field. In the present work, Ag₂S-modified g-C₃N₄ (Ag₂S/g-C₃N₄) composite photocatalysts were prepared via a simple precipitation method. The results demonstrated that the photocatalytic H₂-production activity of g-C₃N₄ can be remarkably increased by the combination of Ag₂S. The optimal Ag₂S loading was found to be 5 wt%, giving a H₂ production of 10 μmol h⁻¹, around 100 times that of pure g-C₃N₄. The enhanced photocatalytic activity can be mainly attributed to the effective charge transfer between g-C₃N₄ and Ag/Ag₂S, of which the latter is formed by simultaneous photodeposition in the photocatalytic H₂ evolution reaction and acts as an efficient co-catalyst for the g-C₃N₄. This work showed the possibility for utilization of Ag₂S or Ag/Ag₂S as a substitute for Pt in the photocatalytic production of H₂ using g-C₃N₄.