Surface treatment-controlled solvothermal synthesis of highly active reduced 1D titania with heterojunctioned carbon allotrope

One-dimensional (1D) nanowire black titania heterojunctioned with multi-wall carbon nanotube (bTiO₂ NW/MWCNT) structures were successfully synthesized via a facile single-step hydrothermal procedure, coupled with succeeding surface treatments and a solid-state physiochemical mode of reduction. Paramagnetic SiO₂-coated Fe₃O₄ microspheres were fabricated and used as cores for the seeding and growth of the bTiO₂ NW/MWCNT photocatalyst. The as-prepared photocatalysts were characterized via X-ray diffraction, scanning electron microscopy, transmission electron microscopy, X-ray photoemission spectroscopy, Fourier transform infrared spectroscopy, and UV-vis diffuse reflectance spectroscopy. The results of materials characterization confirmed formation of 1D bTiO₂ NW structure with chemically bound MWCNT atop the reduced Ti³⁺ propagated lattice of the predominantly (101) exposed facets of anatase TiO₂. Controlling the surface treatment process and NW growth time to maintain the anatase phase and stability of surface morphology upon reduction allowed for superior visible light-driven photoactivity. The visible light-driven photocatalytic degradation of 10 mg/L methylene orange was recorded at 97.4% in 20 min of 0.7 Sun intensity. The apparent reaction rate constant (k) of the as-prepared photocatalyst (0.1439 min⁻¹) is ~ 18 times higher than that of pristine TiO₂. Utilization of paramagnetic cores for in situ photocatalyst collection upon water treatment is highly recommended for newly developed materials. Further, performing surface treatment procedures of prepared titania-based photocatalysts has been proven to have a notable advantageous effect on photoactivity and is thus suggested for similar materials.