Construction of 3D flowers-like O-doped g-C₃N₄-[N-doped Nb₂O₅/C] heterostructure with direct S-scheme charge transport and highly improved visible-light-driven photocatalytic efficiency

Constructing a suitable heterojunction photocatalytic system from two photocatalytic materials is an efficient approach for designing extremely efficient photocatalysts for a broader range of environmental, medical, and energy applications. Recently, the construction of a step-scheme heterostructure system (hereafter called the S-scheme) has received widespread attention in the photocatalytic field due to its ability to achieve efficient photogenerated carrier separation and obtain strong photo-redox ability. Herein, a novel S-scheme heterojunction system consisting of 2D O-doped g-C₃N₄ (OCN) nanosheets and 3D N-doped Nb₂O₅/C (N-NBO/C) nanoflowers is constructed via ultrasonication and vigorous agitation technique followed by heat treatment for the photocatalytic degradation of Rhodamine B (RhB). Detailed characterization and decomposition behaviour of RhB showed that the fabricated material shows excellent photocatalytic efficiency and stability towards RhB photodegradation under visible-light illumination. The enhanced performance could be attributed to the following factors: fast charge transfer, highly-efficient charge separation, extended lifetime of photoinduced charge carriers, and the high redox capability of the photoinduced charges in the S-scheme system. Various trapping experiment conditions and electron paramagnetic resonance provide clear evidence of the S-scheme photogenerated charge transfer path, meanwhile, the RhB mineralization degradation pathway was also investigated using LC-MS. This study presents an approach to constructing Nb₂O₅-based S-scheme heterojunctions for photocatalytic applications.