Environmental and energy problems have drawn much attention owing to rapid population growth and accelerated economic development. For instance, photocatalysis, "a green technology", plays an important role in solar-energy conversion owing to its potential to solve energy and environmental problems. Recently, many efforts have been devoted to improving visible-light photocatalytic activity by using titanium dioxide as a photocatalyst as a result of its wide range of applications in the energy and environment fields. However, fast charge recombination and an absorption edge in the UV range limit the photocatalytic efficiency of TiO under visible-light irradiation. Many investigations have been undertaken to overcome the limitations of TiO and, therefore, to enhance its photocatalytic activity under visible light. The present literature review focuses on different strategies used to promote the separation efficiency of electron-hole pairs and to shift the absorption edge of TiO to the visible region. Current synthesis techniques used to elaborate several nanostructures of TiO -based materials, recent progress in enhancing visible photocatalytic activity, and different photocatalysis applications will be discussed. On the basis of the studies reported in the literature, we believe that this review will help in the development of new strategies to improve the visible-light photocatalytic performance of TiO -based materials further.

We report the elaboration of novel BN/TiO2 composite nanofibers with different amounts of BN sheets and their photocatalytic activity under UV irradiation.

Reduced graphene oxide (rGO) / Titanium dioxide (TiO2) composite nanofibers as photocatalytic materials were successfully elaborated by using electrospinning. The as-spun nanofibers with controlled ratio of rGO were annealed at 500°C under Nitrogen in a tubular furnace.Structural, morphological and optical characterizations demonstrate the success of rGO incorporation in the TiO2 nanofibers. The performances of these nanocomposites for photocatalytic application have been evaluated. The presence of rGO sheets decreases the band gap energy of TiO2 NFs from 3.2 eV to 2.9 eV. Hence, in the photodegradation of methyl orange (MO), a significant enhancement in the reaction rate was observed with rGO/TiO2 (2wt. %) composite NFs compared to commercial TiO2-P25. In addition, the kinetic of MO degradation by rGO/TiO2 (2wt. %) composite NFs is 6 times higher than that by commercial TiO2. Thus, the photocatalytic activity of the composites rGO/TiO2 significantly increases the visible light photo-response and improves the separation of photo-induced electron-hole pairs of TiO2.

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