Synergistic enhancement of the photocatalytic activity of g-C3N4 via in-situ surface alkalization and CQDs loading strategies

The CQDs/alkaline carbon nitride heterojunction photocatalysts were synthesized employing dicyandiamide as the nitrogen material, Citric acid was used as the carbon source, while KCl and NH4Cl were as alkaline reagents. The study investigated the influence of CQDs on the adsorption performance, photocatalytic activity, and band structure of alkalized carbon nitride. The dark adsorption results revealed that CNK/CQDs1: 12 exhibited outstanding adsorption performance, capable of degrading adsorbed pollutants in a relatively short period. The photocatalytic degradation study demonstrates that CNK/CQDs1:12 exhibits significantly higher degradation efficiencies compared to the pristine CN and alkalinized CNK samples, with degradation efficiencies of 94.4 % for Methylene Blue (MB) and 71.68 % for tetracycline hydrochloride (TC-HCl) within 60 min. This is due to the synergistic effects of alkalization of the g-C3N4 surface and CQDs loading, which modified the heterojunction interfacial charge transfer efficiency, suppressing the recombination of photoelectron-hole pair, extending the life span of transient photogenerated carriers, thereby improving photocatalytic activity. Free radical trapping experiment indicated that h+ and ·O2− are the primary active species during the photocatalytic degradation process of CNK/CQDs1:12. [Display omitted] •Surface alkalization and CQDs loading synergistic enhance photocatalytic activity CNK/CQDs heterojunction.•Outstanding adsorption properties of CNK/CQDs1:12 facilitate the photocatalytic degradation of contaminants.•Removal rate of CNK/CQDs1:12 on methylene blue and tetracycline hydrochloride were 94.4% and 64.4%, respectively.