Synthesis of g-C3N4/Nb2O5 heterostructures and their application in the removal of organic pollutants under visible and ultraviolet irradiation

This paper describes the synthesis of a new series of g-C3N4/Nb2O5 heterostructures and their application in the removal of organic pollutants from water, as a combined strategy of photocatalysis and adsorption processes. The heterostructures were synthesized at different weight ratios through thermal oxidation and hydrothermal treatment, leading to an uniform assembly of Nb2O5 nanoparticles onto g-C3N4 surface. The heterostructures exhibited improved textural and electronic properties (narrowing in band gap) when compared to pure g-C3N4 and Nb2O5, respectively. Although adsorption capacities were shown to be influenced by Nb2O5 content, g-C3N4 was essential to increase the photocatalytic response of the g-C3N4/Nb2O5 heterostructures, which displayed an enhancement of photocatalytic performance on the degradation of methylene blue and rhodamine B dyes under visible and ultraviolet irradiation. The enhanced photoactivity was explained by the increase in the lifetime of the charge carries due to formation of heterojunctions between Nb2O5 and g-C3N4. A mechanistic investigation on the photocatalytic process was conducted by using different reactive scavenger species. The superoxide (O2−
- ) radical was found to be the main active specie on the dye photodegradation activated by visible radiation.