Magnetically separable ZnFe2O4 grafted g-C3N4/rGO ternary nanocomposites for enhanced photo-Fenton catalytic activity under visible light

Abstract

Ternary nanocomposites (TNCs) comprising layered functional materials with favorable band edge positions have been strategically employed to suppress the photogenerated carrier recombination and augment photocatalytic performance by harnessing the entire UV–visible–near infrared broadband spectrum. Utilizing the intrinsic magnetic properties of the co-catalysts, a series of easily separable and recyclable g-C3N4/rGO/ZnFe2O4 (CNGZF) TNCs were developed by modulating g-C3N4 mass fraction. The heterogeneous photo-Fenton performances of the TNCs were evaluated in the discoloration of methylene blue with/ or without H2O2 under visible light. The photocatalytic efficacy of TNCs with a mass ratio of 2:1:1 (i.e., 2-CNGZF) surpasses the individual merits of their counterparts, g-C3N4 and ZnFe2O4 by 11.08 and 2.91 times, respectively, and binary composite CNZF (g-C3N4/ZnFe2O4) by 2.34 times in dye degradation. In the presence of H2O2, the highest removal efficiencies of more than 93% (k = 0.0442 min−1) and 97% (k = 0.1922 min−1) were achieved within 60 min and 20 min under artificial visible light and solar irradiation, respectively. Controlling various operational parameters of the reaction medium, a remarkable improvement in the rate constant up to 0.229 min−1 was obtained for 15 mg of catalysts loading using an H2O2 concentration of 0.15 M at pH 7. The enhanced photocatalytic performances are corroborated by a large number of induced active sites, resulting from special dimension effects of the layered nanosheets, broadband absorption capabilities of the co-catalysts, and accelerated electron migration through the metallic counterparts. Electrochemical impedance spectroscopy measurements further confirm the lower interfacial charge transfer resistance and prolonged lifetime of electrons in the TNCs. Furthermore, the moderate magnetic properties of the co-catalysts ease the catalyst recovery process, exhibiting excellent stability and durability even after recycling up to four successive runs.