One pot synthesis of novel C3N4/C nanosheet composites under environmental benign molten salts for peroxymonosulfate activation with enhanced efficiency and reusability

The application of g-C3N4 based carbon materials in peroxymonosulfate (PMS) activation has faced challenges due to the electrochemically inert nature of nitrogen without light irradiation. In this study, two types of crystalline C3N4/C nanosheet composite catalysts were synthesized from glucose and dicyandiamide (DCD) via molten salt-assisted pyrolysis, denoted as M-GD and M-GD2. Both the composite catalysts showed significant improvement in the degradation of acid orange 7 amid PMS activation, taking the advantages of high graphitic N content and defect degree. Specifically, M-GD2 with excessive dosage of DCD exhibited a record catalyst specific activity value (0.0925 L min−1 m−2) in comparison with conventional C3N4 based carbon catalysts. The study also examined the effects of catalyst and PMS concentrations, temperatures, initial pH, and impurity ions on catalytic activity, as well as the catalytic performance in actual sludge wastewater cases. Notably, the M-GD2 catalyst exhibited exceptional regeneration capacity after four consecutive tests, attributed to its unique 3D structure comprising g-C3N4 nanoparticles loaded on crystalline C3N4/C nanosheets. Mechanism analysis revealed that a non-radical mechanism predominantly drove the PMS activation reaction, primarily involving catalyst-mediated electron transfer and surface-bound radicals due to the formation of catalyst-PMS* complexes. This work presents a facile and economical method for preparing defect-rich crystalline C3N4/C nanosheet composite with high graphitic N content, highlighting its catalytic activity, reusability, and regeneration performance synchronously. These findings contribute to advancing the field of PMS activation and offer promising applications in water environment remediation.