Constructing 2D/2D La2Ce2O7/g-C3N4 S-scheme heterojunction for markedly enhanced interfacial charge separation and photocatalytic activity under visible light irradiation

It is an effective strategy to improve photocatalytic degradation performance by constructing step scheme (S-scheme) heterojunction photocatalysts with superior photo-redox capacity and high charge transfer efficiency. In this study, a series of two-dimensional/two-dimensional (2D/2D) La2Ce2O7/g-C3N4 (LCO/CN) S-scheme heterojunction photocatalysts were synthesized via in-situ solid-phase sintering by regulating the mass ratio of raw materials. The large junction area between La2Ce2O7 nanosheets and ultra-thin graphitic carbon nitride (g-C3N4) endows the composite with significantly enhanced separation and transfer efficiency of photogenerated carriers within a satisfactory light response region. The LCO/CN-2 composite not only shows the highest photocatalytic activity with a reaction rate constant of 0.02701 min-1 to degrade Rhodamine B (RhB) under visible light irradiation for 90 min but also demonstrates stable reusability after four runs. Moreover, based on the Mott-Schottky calculations, radical trapping experiments, and ESR analysis, ·O2- and ·OH are identified as the main active species, and an S-scheme charge transfer mechanism is suggested to explain the enhanced photocatalytic activity. This work inspires the application of fluorite-type photocatalysts to wastewater purification and environmental restoration.