Weak Interaction between Nickel Thiolate and g-C₃N₄ Improving Electron–Hole Separation for Photocatalysis

Abstract

Developing strategies to accelerate the electron–hole pair separation and understanding the mechanism are important for improving the activity of photocatalysts. Herein, constructing a weak interaction between nickel thiolate cluster (i.e., Ni12(SPhCH3)24) and graphitic carbon nitride (g-C3N4) is revealed as an effective strategy to regulate electron–hole pair separation. The π–π interaction between the triazine rings in g-C3N4 and the phenyl rings in Ni12(SPhCH3)24 offers a primary pathway for photogenerated electrons transfer from nickel cluster to g-C3N4. The photocatalytic hydrogen evolution rate of Ni12(SPhCH3)24/C3N4 achieves ∼3000 μmol g–1 h–1, which is about 230 times higher than that of pure g-C3N4. Theoretical analysis and femtosecond transient absorption spectroscopy show that the photogenerated electrons on the phenyl groups contribute to the unoccupied molecular orbitals (i.e., LUMOs+1) of Ni12(SPhCH3)24 and then transfer to the conduction band of g-C3N4 via the π–π interaction, which eventually results in the spatial electron–hole pair separation and improves the hydrogen evolution activity of the catalyst.