Photocatalytic performance of Nb2O5-graphene heterojunction for the degradation of methylene blue

In this study, a facile hydrothermal method has been successfully applied to elaborate a Nb2O5 and Nb2O5/reduced graphene oxide photocatalyst with uniform spheres structure for the degradation of methylene blue (MB) under UV irradiation. The X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and Brunauer-Emmett-Teller (BET) analysis confirm the formation of the Nb2O5/reduced graphene oxide heterostructure with high surface area (S-BET = 69.21 m(2).g(-1)). The optical properties shows that the Nb2O5/reduced graphene oxide exhibited the lower bandgap value of 2.88 eV as compared to Nb2O5 (3.14 eV) with significant redshift and enhance visible light absorption. The photo-catalytic activity of the Nb2O5 and Nb2O5/reduced graphene oxide photocatalyst for the removal of the methylene blue (MB) under UV-visible illumination was evaluated. The electrochemical impedance spectroscopic (EIS) measurements further elucidate the suppression of photogenerated electrons/holes as the radius of the semicircle significantly decreased in case of heterojunction formation. It was found that the Nb2O5 decorated with reduced graphene oxide sheet showed significantly better photocatalytic efficiency in the removal of methylene blue dye (99.5 % degradation after 1 h of irradiation) than commercial Nb2O5 (20 % degradation after 1 h of irradiation). This result comes from the effective formation of heterojunctions between the reduced graphene oxide and Nb2O5 semiconductor which facilitate the transfer of the photoelectrons from the surfaces of the nanoparticles to the reduced graphene oxide sheets, nanoporous structure with numerous catalytically active sites, superior charge transfer efficiency, and stronger oxidation property of the synthesized nanoparticles.