Accelerating the peroxymonosulfate activation and charge transfer by construction of Fermi energy level-matched CoWO4/g-C3N4 photocatalyst for typical antibiotics degradation

Activation of peroxymonosulfate (PMS) by constructing heterojunctions using cobalt-based catalysts under visible light has been widely used for the treatment of emerging pollutants. However, the high recombination rate of photogenerated charge carrier severely inhibited the degradation efficiency of photocatalysts. Herein, CoWO4/g-C3N4 was prepared as an efficient PMS activator for the degradation of typical antibiotics according to a rational structural and compositional design via the matching principle of Fermi levels. The morphology, structure and chemical composition of the composites were investigated through a series of characterizations. The tetracycline hydrochloride (TCH) degradation efficiency of 2CoWO4/g-C3N4 reached 99.9 % in 10 min at PMS/vis system, with the mineralization performance at 59.8 %. The excellent degradation performance was attributed to the unimpeded photogenerated carrier separation and transfer caused by the matched energy band structure between CoWO4 and g-C3N4. Also, its degradation performance for Ciprofloxacin (CIP) and Norfloxacin (NOF) was better than the reported non-Fermi level matched heterojunction composed of CoWO4 and g-C3N4. The results of quenching experiments verified the production and consumption processes of reactive oxidants O2−, 1O2, SO4− and OH. The degradation pathways and mechanism of TCH were also extrapolated in detail. This research provided an in-depth theoretical basis for the design and construction of highly efficient photocatalysts.