Synergy of dual dopants and nitrogen defects in graphitic carbon nitride for boosting sustainable photocatalytic inactivation efficiency towards antibiotic-resistant bacteria

Dissemination of antibiotic-resistant pathogens in water environment is a global issue that greatly threatens human health. Sustainable water disinfection methods are highly desired for elimination of antibiotic-resistant bacteria (ARB). This work presented a novel strategy of combing dual dopants with nitrogen defects in graphitic carbon nitride (g-C3N4) to construct metal-free photocatalysts for inactivation of ARB under visible light (VL) irradiation. Boron and oxygen co-doped g-C3N4 with N-defects (denoted as OBCN) was synthesized employing oxyacid pre-treatment and NaBH4 co-calcination. The synergy of B and O dopants collectively promoted the formation of N-defects which was characterized by heptazine ring open to produce cyano groups. Band gap was narrowed with the formation of midgap states, leading to extended VL absorption and enhanced separation of photo-excitons, as revealed by both experimental and density functional theory (DFT) calculations. Compared with single doping of B and O, a more obvious electron-rich region was observed in B, O dual doping, which further inhibited the recombination of photo-excitons in OBCN. As a result, the OBCN exhibited superior photocatalytic activities for inactivation of ARB. Complete inactivation of similar to 7.0 log gentamicin-resistant E. coli by OBCN was achieved within 180 min with inactivation rate constant of 0.53 min(-1), which is 7.6 times higher than that of pristine g-C3N4. The contribution of reactive species responsible for ARB inactivation and the bacterial stress response mechanisms were also revealed. This study highlights an innovative strategy of synergy of dual dopants and defects to design renewable photocatalysts for control of ARB pollution using sustainable sunlight energy.