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

Abstract

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.