Facile electrospinning synthesis of S-scheme heterojunction CoTiO3/g-C3N4 nanofiber with enhanced visible light photocatalytic activity

Photocatalysts featuring S-scheme heterojunctions offer considerable potential for both the photocatalytic CO2 conversion and the degradation of antibiotics, providing practical solutions for energy crises and environmental challenges. In this work, 1D/2D CoTiO3/g-C3N4 (CTO/CN) S-scheme heterojunction is synthesized through electrospinning and calcination. The close interweaving of g-C3N4 nanosheets around CoTiO3 nanofibers creates ample contact areas and active sites, resulting in exceptional photocatalytic CO production capability. The optimal mass ratio of CoTiO3 to g-C3N4 is 2%, and the CO and CH4 yields are 46.5 and 0.825 μmol g-1 h-1. Moreover, comparing with monomeric g-C3N4, this composite achieves a better CO yield with 43.5 times and displays an impressive product selectivity of 98.3% for CO2-CO photoreduction. In addition, the 2% CTO/CN photocatalyst demonstrates outstanding photocatalytic degradation efficiency, with degradation rates of 95.88%, 95.53%, and 71.23% for tetracycline hydrochloride, oxytetracycline, and ofloxacin, respectively. These enhanced photocatalytic properties are attributed to the S-scheme system constructed by CoTiO3 with g-C3N4, maintaining strong oxidation-reduction capabilities while efficiently segregating photogenerated charges, with the existence of S-scheme heterojunction confirmed through various analyses. Furthermore, in situ studies and 13C calibration experiments reveal that CO and CH4 originate from the photocatalytic CO2 conversion, further highlighting the potential of this work in advancing CO2 photoreduction. This study offers novel insights into designing effective S-scheme heterojunction photocatalysts for practical applications to address environmental and energy challenges.