Optimization of thermal exfoliation of graphitic carbon nitride for methylparaben photocatalytic degradation under simulated solar radiation

Previous studies have shown that the exfoliation of graphitic carbon nitride (g-C3N4) is essential to obtain materials with good photocatalytic properties. However, in most studies the influence of exfoliation variables was investigated in an unsystematic way by changing the levels of one factor at a time. In this work, a full factorial design 3(2) was employed to evaluate the influence of temperature and time used in the thermal exfoliation of bulk g-C3N4 obtained from urea (bulk-U), on the photocatalytic performance for 5 mg L-1 methylparaben degradation under simulated solar radiation. Based on the thermal stability of the starting bulk-U, the levels of the design were set in the range of 400 to 450 degrees C for temperature and 2 to 6 h for time. The results showed an enhancement in the photocatalytic activity with an increase in both factors, obtaining the maximum response at T = 450 degrees C and t = 6 h. An economic evaluation at the laboratory scale including the main costs derived from the synthesis stage and the photocatalytic degradation procedure was also performed, comparing all the exfoliated materials. The total expenses could be minimized without compromising good photocatalytic activity with the material obtained by exfoliation of bulk-U at 450 degrees C for 2 h. Detailed characterization of the materials was carried out by XRD, FT-IR, adsorption-desorption of N-2, TEM, SEM, UV-Vis DR, and PL spectroscopy. It was inferred that the enhancement of the photocatalytic performance induced by the exfoliation was mainly related to the consequent increase in the surface area and the improvement in the separation of photogenerated charge pairs derived from the unpacking of the stacked layers.

Automated summary

This study investigated the influence of temperature and time on the exfoliation of g-C3N4 using a full factorial design. The results showed that the optimal conditions for obtaining materials with excellent photocatalytic performance were 450℃ for temperature and 6 hours for time. An economic evaluation also demonstrated that these conditions could minimize expenses without compromising photocatalytic activity. Detailed characterization analysis suggested that the enhanced photocatalytic performance induced by exfoliation was mainly attributed to the increased surface area and improved separation of photogenerated charge pairs.