Photocatalytic degradation of nevirapine with a heterostructure of few-layer black phosphorus coupled with niobium (V) oxide nanoflowers (FL-BP@Nb2O5)

The degradation and removal of antiviral drugs in water has emerged remains a major challenge. This work presents, the photodegradation of nevirapine (NVP) with a novel p-n heterostructure of FL-BP@Nb₂O₅ nanoparticles synthesized via hydrothermal method. Several characterization techniques revealed a successful formation of the heterostructure with well aligned band positions that promoted excellent separation of charge carriers. A systematic study was conducted on the effect of initial pH, initial catalyst loading and initial concentration on the degradation kinetics of NVP. Degradation efficiency of 68% was achieved with the FL-BP@Nb₂O₅ after 3 h with 5 ppm initial concentration solution of NVP, at a working pH of 3 and 15 mg of photocatalyst. The stable fragment resulting from the degradation of NVP was n-butanol as evidenced by LC/MS. The successful degradation of NVP transpired with synergistic effect exhibited by the heterostructure that led to accelerated formation of reactive species that were responsible for the breaking down of NVP into smaller fragments. A TOC removal percentage of 19.03% after the photodegradation of NVP was observed, suggesting a successful break down of NVP to simpler non-toxic carbon-containing compounds.

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

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.