This study examines the effects of the TiO2 content and TiO2 position in the core or shell within tubular carbon nanofibers on the photocatalytic activity under visible light. Core–shell tubular carbon nanofiber composites whose cores are filled with TiO2 nanoparticles (PMTi(10)P) are fabricated through coaxial electrospinning and subsequent heat treatment. The PMTi(10)P composites with well-preserved TiO2 nanoparticles in the core part induce more oxygen vacancies, Ti3+ species, chemisorbed oxygen species, and anatase phases, significantly improving the photocatalytic performance. They act as photoelectron traps, allowing more photoelectrons and holes to participate in the photocatalytic reaction and extending the absorbance of TiO2 to the visible light region. The resulting PMTi(10)P photocatalyst exhibits excellent performance of 100% removal of methylene blue within 30 min and maintains nearly 100% removal of 15 ppm methylene blue over 10 regeneration cycles, indicating consistent and stable photocatalytic performance.

Optimization of the TiO2 content and location in core–shell tubular carbon nanofibers to improve the photocatalytic activity under visible light irradiation
    Abstract
    1 Introduction
    2 Experimental
        2.1 Materials and fabrication
        2.2 Characterization
    3 Results and discussion
    4 Conclusions
    Acknowledgements 
    References

• Bo‑Hye Kim(Department of Chemistry Education, Daegu University, Gyeongbuk 38453, Republic of Korea) Corresponding author