The heterojunction structure of semiconductor photocatalysts is significant for making full use of their capabilities for organic molecules and dye degradation. In this paper, we present a heterogeneous junction composite fabricated with hybrid phase TiO2 and g-C3N4 for methylene blue (MB) removal through adsorption and photocatalytic degradation. The heterogeneous junction system was prepared by hydrothermal treatment with a subsequent pyrolysis process. The variation of the proportion and lattice structure of hybrid phase TiO2 in the synthesized catalysts was analyzed by refinement. Adsorption experiments showed that the maximum adsorption capacity of TiO2/g-C3N4 (1 : 10) was 1667 mg g−1, which was 45.97 times and 63.78 times higher than that of TiO2 and g-C3N4, respectively. In the photodegradation process, the TiO2/g-C3N4 (1 : 10) photocatalyst shows a removal rate of MB of 100 mg L−1, which was as high as 96.262%, significantly higher than that of pure TiO2 and g-C3N4. Brunner–Emmett–Teller (BET) measurements and Fourier transform infrared spectroscopy (FTIR) showed that the adsorption of MB onto TiO2/g-C3N4(1 : 10) was chemical adsorption, and ˙OH, which acts as an active substance, was found to play a major role in the photocatalytic degradation process. Overall, the developed hybrid phase TiO2/g-C3N4 heterojunction composite may be beneficial for the treatment of water pollution.
In order to achieve excellent visible light photoactivity of TiO 2 , it is still urgently required to extend their optical absorption ability and improve the potential of charge separation and migration. Here we synthesized highly efficient visible-light-active catalysts F-TiO 2 /g-C 3 N 4 via a one-step-calcination method. Due to the synergic effect of ≡Ti−F, ≡Ti:F−H and the heterojunction, the obtained catalysts possess promising properties as highly efficient separation and migration of photoelectron-hole pairs. The prepared F-TiO 2 /g-C 3 N 4 heterojunction can be successfully applied to degrade the widely used flame retardants and antibiotics. More than 95% of tetrabromobisphenol A (TBBPA) was decomposed after light illumination for 120 min, and 98% of sulfamethazine (SMZ) was degraded for 60 min by F-TiO 2 /g-C 3 N 4 . Furthermore, a reasonable catalytic mechanism for the F-TiO 2 /g-C 3 N 4 catalysts was proposed. It could be seen that the active species •O 2 − , •OH, and h + played important roles in the photocatalytic process under visible light illumination.
Hydrogen evolution and dye degradation catalyzed by environmentally benign and inexpensive photocatalyst in aqueous solution is regarded as a promising avenue to effectively address the global energy and environmental crisis. It is difficult for traditional photocatalysts to perform efficient light harvesting, with conducive recycling and promoted charge separation and transport, which limit practical applications in photocatalytic conversion. In this study, a facile template-assisted coaxial electrospinning approach was explored to successfully build close contacted heterojunctions within the interface of g-C3N4 nanosheets and hollow porous TiO2 nanofibers, which significantly increased the separation efficiency of photo-induced electron–hole pairs in the visible-light region. A hollow and porous structure with abundant surface-active sites assisted in inducing multiple light reflection for more efficient light harvesting. Moreover, one dimensional TiO2/g-C3N4 composite nanofibers with a large length-to-diameter ratio would be more attractive for recovery. At the optimal g-C3N4 loading, hollow porous TiO2/g-C3N4-50% nanofibers exhibited the highest rate of hydrogen evolution and RhB degradation. The enhanced photocatalytic performance of hollow porous TiO2/g-C3N4 composite photocatalysts was mainly attributed to the synergistic effect of the hollow porous architecture and heterojunction. This work might make a significant contribution to insight into preparing hollow structure heterogenous nanofiber photocatalysts with improved activities in hydrogen generation and pollutant degradation.
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