S-scheme N-doped carbon dots anchored g-C3N4/Fe2O3 shell/core composite for photoelectrocatalytic trimethoprim degradation and water splitting

Photoelectrocatalysis is a promising technique for energy conversion and environmental treatment. This study describes the photoelectrochemical (PEC) degradation of trimethoprim and hydrogen evolution using a photoanode prepared by N-doped carbon dots (NCD) incorporated g-C3N4/α-Fe2O3 (CNFO) shell/core nanocomposite. The electrochemical analysis reveals that the photocurrent density of NCD@CNFO photoanode reached 3.07 mA cm−2 at 1.6 V vs. NHE, which is 4 and 15 times greater than that of CNFO and intact α-Fe2O3, respectively. In the presence of peroxymonosulfate (PMS), the NCD@CNFO photoanode enabled 95 % and 90 % of trimethoprim (TMP) degradation in aqueous solution and lake water, respectively. Hydrogen generation coupled with TMP degradation was also observed in the PEC system, where the H2 generation rate was 550 µmol cm−2 h−1. Both superoxide (•O2−) and hydroxyl (•OH) radicals played a significant role in the degradation of TMP. The achievements could be assigned to the excellent photoabsorption and electron transfer properties of NCD, which enhanced the PEC activity of CNFO by enabling the S-scheme heterojunction to reduce electron-hole recombination. Moreover, PMS served as a cathodic electron acceptor to improve the catalytic properties of NCD@CNFO photoanode, demonstrating its contribution to both water treatment and hydrogen production. Such superior efficiency offers great potential to develop a PEC system using carbon dots/semiconductor hybrid catalysts for antibiotic degradation and synchronous photocatalytic H2 evolution from wastewater, providing an alternative solution to environmental pollution and energy crisis issues.