The presence of organic contaminants such as pesticides, pharmaceuticals, and dyes in rivers and lakes, even at low concentrations, can seriously affect human health and the environment1. There is therefore a need for the development of efficient treatment technologies for the removal of these compounds from wastewater. Advanced oxidation processes (AOPs) such as heterogeneous photocatalysis have attracted great interest for this purpose, especially using semiconductors that can be actived under visible irradiation. Graphitic carbon nitride (g-C3N4) is gaining attention in photocatalysis due to its semiconducting properties, which allow its activation by visible radiation. This material is of particular interest because of the increasing use of solar energy in many applications, but previous studies have found that g-C3N4 is more useful when associated with another semiconductor in a heterostructured system such as AgVO3/g-C3N42, g-C3N4/TiO23 . Among several materials with high potential to form heterostructures with g-C3N4, Nb2O5 is an especially interesting material due to its electronic properties. Nb2O5 is also well known for its strong surface acidity, which is useful for the adsorption and subsequent degradation of organic pollutants. Therefore, we propose a synthesis route for the production of suitable heterostructures using a sonochemical method based on surface charge-induced heteroaggregation. In this work we was focus shown that the g-C3N4/Nb2O5 heterojunctions with different weight ratios between g-C3N4 and Nb2O5, enhanced the photocatalytic performance for degradation of emerging pollutants (drug amiloride and rhodamine B dye) under visible irradiation, compared to the pure semiconductors. The photodegradation performances were mainly associated with increased lifetimes of the charge carriers, due to the formation of heterojunctions between Nb2O5 and g-C3N4. Formation of the type II heterostructure was confirmed by time-resolved photoluminescence, with the 3CN:1Nb heterostructure showing the longest electron/hole pair lifetime. Studies of the photodegradation mechanism confirmed that the hole (i.e., direct oxidation) was the main active species for dye photodegradation catalyzed by the g-C3N4/Nb2O5 heterostructures under visible irradiation. Additionally, it was demonstrated that the g-C3N4/Nb2O5 heterostructures exhibited satisfactory photostability, even after four successive reuses. Therefore, our work demonstrates the possibility of achieving significant improvements in the catalytic performance of two different semiconductors, g-C3N4 and Nb2O5, by means of their association.
Keywords: Graphitic carbon nitride; Sonochemical method; Heterojunction; Photooxidation;
Work supported by Fapesp, LNNano, MCTI/SisNANO, CNPq and CAPES.
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