Abstract:

Constructing heterojunction between two semiconductors with matched energy band structure is an effective modification method to obtain excellent photocatalysts. The experimental scheme adopts a simple solvent method to self-assemble nitrogen doped carbon dots (N-CDs) on the surface of sulfur doped carbon nitride (S-C₃N₄) semiconductor through π-π conjugate interaction. Based on this, a novel 0D/2D S-scheme heterojunction N-CDs/S-C₃N₄ hybrid was successfully prepared. The degradation kinetic constants of N-CDs/S-C₃N₄ for rhodamine B (RhB) and p-nitrophenol (PNP) reached 0.23522 and 0.01342 min^-1, respectively, which were 2.72 and 2.65 times that of S-C₃N₄. The highest photocatalytic hydrogen evolution rate was observed under the simulated sunlight irradiation, which was 2.30 times that of S-C₃N₄. The improvement of photocatalytic performance was mainly based on the formation of the S-scheme heterojunction between S-C₃N₄ and N-CDs. The effects of internal electric field, π-π conjugate interaction and band bending promoted the photogenerated h⁺and e^- with low redox ability to recombine and retained the beneficial h⁺and e^- with strong redox ability, which contributed to the production of more active species of h⁺and •O₂^-, therefore the photocatalytic degradation and hydrogen evolution performance were significantly enhanced.

Key words: S-scheme, Internal electric field, Hydrogen evolution, C₃N₄, π-π interaction