Facile ball-milling synthesis of CeO2/g-C3N4 Z-scheme heterojunction for synergistic adsorption and photodegradation of methylene blue: Characteristics, kinetics, models, and mechanisms

Abstract As a green solvent-free process, ball milling has attracted considerable attention in fabricating nanocomposites. Herein, we synthesized novel Z-scheme heterojunction CeO2/g-C3N4 nanocomposites by simply direct ball milling CeO2 and g-C3N4 at three different mass ratios (3:7, 7:3, and 9:1). In comparison to individual CeO2 and g-C3N4, the ball-milled nanocomposites showed stronger UV light response, higher charge carrier separation efficiency, greater photodegradation potential, higher photocurrent intensity, and faster electron transfer, indicating much better photocatalytic activity. When used as photocatalysts to remove methylene blue (MB) under UV light irradiation, 70% CeO2/g-C3N4 exhibited the highest removal rate (90.1%), much better than that of CeO2 (6.2%) or g-C3N4 (45.7%). The synergistic interact between adsorption and photodegradation of the CeO2/g-C3N4 nanocomposites was simulated by kinetic models, and a strong positive correlation (r=0.834 and rs=0.777) between adsorption and photocatalysis was identified. The results indicate that adsorption can promote photodegradation by accelerating the kinetics, while photodegradation can regenerate adsorption sites. This work provides not only a facile synthesis of Z-scheme heterojunction photocatalysts but also a novel perspective for better understanding the synergy between adsorption and photocatalysis.