Construction of Novel Type-II SrTiO3/g-C3N4 Heterojunction Photocatalysts: Photodegradation of Tetracycline and Photocatalytic Mechanism

Graphite-like carbon nitride (g-C3N4) has attracted wide attention in the field of photocatalysis due to its simple and feasible preparation method and appropriate energy gap structure for light absorption in a wide range. However, its high recombination rate of photo-generated electrons and holes affects its catalytic efficiency. In this paper, type II strontium titanate/graphite-like carbon nitride (SrTiO3/g-C3N4) heterojunction photocatalysts were designed and prepared by mixed calcination method. The results of XRD and IR spectra have showed that the two semiconductors were well combined. The wider light absorption range was found in the 10 wt % SrTiO3 composite materials by UV–Vis diffuse reflection spectrum, and it was proved that the recombination of photo-generated electrons and holes was greatly reduced by PL spectrum and photoelectric tests. The photocatalytic degradation ratio of 10 wt %–SrTiO3/g-C3N4 composite materials was about 56 times higher than that of pure g-C3N4 by degrading tetracycline drugs (TCN), and the performance of photocatalytic degradation of TCN still remained at about 96.4% after five cycles. The photocatalytic mechanism analysis indicates that the type-II heterojunction photocatalysts are formed between SrTiO3 and g-C3N4 composite materials, and the reasons for improving photocatalytic degradation efficiency of TCN are explained.