Intercalation of Nb2O5 nano-flowers into the walls of few-layer black phosphorus creating a heterostructure of FL-BP@Nb2O5 with the potential for environmental application

Abstract

Herein we report the successful exfoliation of few-layer BP (FL-BP) from bulk BP via ultrasonication in N-methylpyrrolidone (NMP). FL-BP exhibited an orthorhombic phase structure similar to that of bulk BP with weak electrostatic out-of-plane interactions and strong ionic in-plane bonds. The weakened out-of-plane bonds allowed the intercalation of Nb₂O₅ nano-flowers that were hydrothermally synthesized, forming an intimate contact with the exfoliated BP. The successful formation of the heterointerface was confirmed by the co-existence of crystal phases of both compounds as per the XRD results. The formation of the new intrinsic Nb–P bond was confirmed by the presence of Raman shoulders of both compounds, further substantiated by the XPS analysis. The heterointerface enhanced Nb₂O₅ light-harvesting capacity as per the UV-vis measurements. The FL-BP's properties of higher carrier effective mass and density were successfully incorporated in the composite, implying an increased flow of electrons in the composite's lattice structure. This was displayed by the great suppression of the fast recombination rate of charge carriers in the composites. The 3% BP@Nb₂O₅ composite exhibited excellent optoelectrical properties, compared to the other composites, as suggested by the microstrain calculations, PL, and the EIS data. Mott–Schottky plots verified the p–n type heterojunction formed in the composites, and further verified the increased electron density/concentration in the composites, with respect to Nb₂O₅. Noteworthy, the incorporation of FL-BP in the lattice of Nb₂O₅ increased the surface area and the pore size and volume, which is a character beneficial for photocatalysis as it presents active sites and diffusion pathways.