Enhanced photocatalytic degradation and H2 evolution performance of N CDs/S-C3N4 S-scheme heterojunction constructed by π-π conjugate self-assembly

Abstract

• Novel 0D/2D N CDs/S-C 3 N 4 S-scheme heterojunction was prepared by a simple solvent evaporation induced self-assembly method. • FT-IR and HRTEM confirmed that N CDs were supported on S-C 3 N 4 through π-π conjugate interaction. • N CDs/S-C 3 N 4 demonstrated superior photocatalytic performance in degrading organic pollutants and hydrogen evolution. • The enhanced photocatalytic activity was attributed to the formation of S-scheme heterojunction with high redox potentials. 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-C 3 N 4 ) semiconductor through π-π conjugate interaction. Based on this, a novel 0D/2D S-scheme heterojunction N CDs/S-C 3 N 4 hybrid was successfully prepared. The degradation kinetic constants of N CDs/S-C 3 N 4 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-C 3 N 4 . The highest photocatalytic hydrogen evolution rate was observed under the simulated sunlight irradiation, which was 2.30 times that of S-C 3 N 4 . The improvement of photocatalytic performance was mainly based on the formation of the S-scheme heterojunction between S-C 3 N 4 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 • O 2 − , therefore the photocatalytic degradation and hydrogen evolution performance were significantly enhanced.