Optimization of the TiO2 content and location in core–shell tubular carbon nanofibers to improve the photocatalytic activity under visible light irradiation

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.