Modulation of Exposed Active Sites and Electronic Structure of Co-Doped Carbon Nitride Achieving Enhanced Activity toward Peroxymonosulfate Activation for Antibiotic Degradation

Co-doped carbon nitride (CoCN-6NH4Cl) was prepared through an NH4Cl-assisted pyrolysis method. The catalyst exhibits enhanced and persistent activity toward peroxymonosulfate (PMS) activation for antibiotic degradation under visible light. The levofloxacin (LEV) removal efficiency reaches 89.1% within 60 min, much higher than that of the catalyst (CoCN) prepared without addition of NH4Cl (65.0%). Moreover, the decay of the LEV removal efficiency after four cycles over CoCN-6NH4Cl is only 7.6%, in contrast to 21.8% over CoCN. The enhanced activity of CoCN-6NH4Cl can be attributed to the remarkably increased specific surface area to expose more active sites as well as the modified electronic structure caused by Cl doping. The improved charge separation efficiency of CoCN-6NH4Cl results in the generation of more photogenerated holes (h+), superoxide radicals (·O2–), and singlet oxygen (1O2) as main active species participating in the LEV degradation, thus greatly promoting the degradation efficiency. This work provides a facile and effective strategy to develop high-performance catalysts in advanced oxidation processes.