Triangle CeO2/g-C3N4 heterojunctions: Enhanced light-driven photocatalytic degradation of methylparaben

In this work, an efficient photocatalytic system for methylparaben (MP) removal, using solar (λ > 360 nm) and visible (λ > 420 nm) light-driven CeO₂/g-C₃N₄ (CeO₂/CN) heterojunctions is reported for the first time. The physicochemical properties of pure CeO₂, CN, and CeO₂/CN composites were investigated using characterization techniques, such as XRD, FESEM-EDS, TEM, UV–Vis, PL, XPS, and electrochemical spectroscopy. Among the catalysts with different mass ratios of CeO₂, 10 %CeO₂/CN showed the best photocatalytic performance. This is attributed to the enhanced charge carrier’s separation because of the proper band-edge alignment between CN and CeO₂ components, and the strong visible light absorbance. The photocatalytic degradation of MP followed the first-order kinetics, and the 10 %CeO₂/CN catalyst exhibited a 3.8- and 11.3-times higher reaction rate (k) constant than that of pure CN, investigated under solar and visible light illumination, respectively. Further, scavenger trapping experiments confirmed that hydroxyl radicals (OH^.) and dissolved oxygen are the predominant active species in MP oxidation over 10 %CeO₂/CN composite catalyst. ¹H NMR and LCMS-HPLC results and observations showed complete degradation of MP (0.1 g/L) to CO₂ and H₂O after 7 h of solar irradiation, due to the absence of the representative peaks of MP and its organic degradation products (e.g. phenols, benzoates).