Triggering n→π∗ electronic transitions by thiazole modified graphitic carbon nitride for enhanced photocatalytic hydrogen peroxide production and Rhodamine B degradation

Abstract

Graphitic carbon nitride (g-C₃N₄, GCN) catalyst is widely used in photocatalytic oxygen reduction for hydrogen peroxide (H₂O₂) production and photocatalytic degradation of pollutants. However, its photocatalytic activity is restricted by its narrow light response range and low efficiency of photogenerated charge disjunction and transfer. In this work, thiazole modified g-C₃N₄ is prepared by Schiff-base condensation reaction of benzothiazole-2-carboxaldehyde (2-BTCA) and CN. It was found that grafting thiazole structures onto the conjugated polymer effectively alter the original symmetrical structure of carbon nitride, thereby triggering n→π∗ electronic transitions, intensifying light absorption capability, and increasing the charge carrier migration rate. Benefiting from these advantages, the H₂O₂ yield catalyzed by thiazole modified g-C₃N₄ (SCN-5) reaches up to 513.2 μmol L⁻¹ within 90 min, which is about 2.2 times that of pure g-C₃N₄. Because of this, thiazole ring modified g-C₃N₄ can be efficiently degrade dye pollutants, for instance remove within 60 min up to 96.0 % of Rhodamine B (RhB), which is remarkably greater than that obtained with pure g-C₃N₄ (66.2 %). Both density functional theory (DFT) calculations and experimental results demonstrate that the introduction of thiazole rings improves adsorption capacity for O₂ and RhB molecules. This facilitates the production of •O₂⁻ and enhances the activation and degradation of RhB molecules, thereby boosting photocatalytic performance. This research provides an effective new strategy for improving oxygen activation and offers a straightforward method for practical application of bifunctional photocatalysts.