Evaluation of Efficient and Noble-Metal-Free NiTiO3 Nanofibers Sensitized with Porous gC3N4 Sheets for Photocatalytic Applications

One-dimensional nickel titanate nanofibers (NiTiO3 NFs) were synthesized and loaded with acetic acid-treated exfoliated and sintered sheets of graphitic carbon nitride (AAs-gC(3)N(4)) to fabricate a unique heterogeneous structure. This novel fabrication method for porous AAs-gC(3)N(4) sheets using acetic acid-treated exfoliation followed by sintering provided gC(3)N(4) with a surface area manifold larger than that of bulk gC(3)N(4), with an abundance of catalytically active sites. Hybrid photocatalysts were synthesized through a two-step process. Firstly, NiTiO3 NFs (360 nm in diameter) were made by electrospinning, and these NiTiO3 NFs were sensitized with exfoliated gC(3)N(4) sheets via a sonication process. Varying the weight ratio of NiTiO3 fibers to porous AAs-gC(3)N(4) established that NiTiO3 NFs containing 40 wt% of porous AAs-gC(3)N(4) exhibited optimal activity, i.e., removal of methylene blue and H-2 evolution. After 60 min exposure to visible light irradiation, 97% of the methylene blue molecules were removed by the hybrid photocatalyst, compared with 82%, 72%, and 76% by pristine AAs-gC(3)N(4), NiTiO3 NFs, and bulk gC(3)N(4), respectively. The optimal structure also displayed excellent H-2 evolution performance. The H-2 evolution rate in the optimal sample (152 mu mol g(-1)) was 2.2, 3.2 and 3-fold higher than that in pure AAs-gC(3)N(4) (69 mu mol g(-1)), NiTiO3 NFs (47 mu mol g(-1)) and bulk gC(3)N(4) (50 mu mol g(-1)), respectively. This clearly shows that the holey AAs-gC(3)N(4) nanosheets interacted synergistically with the NiTiO3 NFs. This extended the lifetime of photogenerated charge carriers and resulted in superior photocatalytic activity compared with pristine NiTiO3 NFs and bulk gC(3)N(4). The higher Brunauer-Emmett-Teller surface area and the presence of many catalytically active sites also enhanced the photocatalytic performance of the hybrid sample. Moreover, through photoluminescence and photocurrent response analysis, a significant decrease in the recombination losses of the hybrid photocatalysts was also confirmed. Thus, this is a novel strategy to fabricate highly efficient photocatalysts with precisely tunable operating windows and enhanced charge separation.

Automated summary

One-dimensional nickel titanate nanofibers were loaded with acetic acid-treated exfoliated and sintered graphitic carbon nitride sheets to fabricate a unique heterogeneous structure, resulting in a hybrid photocatalyst with significantly enhanced activity for methylene blue removal and hydrogen evolution. The synergistic interaction between the holey AAs-gC(3)N(4) nanosheets and NiTiO3 NFs extended the lifetime of photogenerated charge carriers, leading to superior photocatalytic performance compared to pristine NiTiO3 NFs and bulk gC(3)N(4). The hybrid sample also exhibited reduced recombination losses, indicating precise tunable operating windows and enhanced charge separation.