Hydroxyl-/Carboxyl-Rich Graphitic Carbon Nitride/Graphene Oxide Composites for Efficient Photodegradation of Reactive Red 195 and Antibacterial Applications

In this work, a protonated graphitic carbon nitride (P-g-C3N4)-coated graphene oxide (GO) composite (GO/P-g-C3N4) was prepared via wet-chemistry exfoliation, followed by a freeze-drying process. The GO/P-g-C3N4 composite was found to have an outstanding photodegradation performance effect on the reactive red 195 (RR195) dye and very strong antibacterial properties. Both the GO structure and the dispersed state of P-g-C3N4 were found to play a significant role in enhancing the photocatalytic activity of GO/P-g-C3N4. The GO/P-g-C3N4 obtained via freeze-drying retained a large number of oxygen-containing groups and showed higher catalytic activity and reusability than the reduced GO (rGO)/g-C3N4 obtained via thermal reduction. Characterization of the samples indicates that GO/P-g-C3N4 has a higher specific surface area and photocurrent density than rGO/g-C3N4; it is likely that these properties lead to the superior photocatalytic activity observed in GO/P-g-C3N4. Adsorption energy calculations indicate that O2 can be readily adsorbed onto the GO surface, which results in stronger oxidizing superoxide anion radicals (center dot O2-) and holes (h+); these active radicals can rapidly degrade RR195 dyes. Moreover, broad-spectrum antibacterial activity (demonstrated against Staphylococcus aureus and Escherichia coli) was observed in the case of the GO/P-g-C3N4 composite irradiated with visible light. This work offers new insights into the design of cost-effective g-C3N4-based photocatalysts for environmental remediation.

Automated summary

A composite of protonated graphitic carbon nitride-coated graphene oxide (GO/P-g-C3N4) was prepared using wet-chemistry exfoliation and freeze-drying. The GO/P-g-C3N4 composite showed excellent photodegradation performance and strong antibacterial properties. The structure of GO and the dispersed state of P-g-C3N4 played a significant role in enhancing the photocatalytic activity. Compared to reduced GO (rGO)/g-C3N4, the GO/P-g-C3N4 obtained through freeze-drying retained more oxygen-containing groups, resulting in higher catalytic activity and reusability. The GO/P-g-C3N4 exhibited a higher specific surface area and photocurrent density, leading to superior photocatalytic activity. Adsorption energy calculations revealed that O2 can be readily adsorbed onto the GO surface, generating stronger oxidizing superoxide anion radicals and holes, which rapidly degrade dyes. The GO/P-g-C3N4 composite also exhibited broad-spectrum antibacterial activity when irradiated with visible light. This work provides new insights into the design of cost-effective g-C3N4-based photocatalysts for environmental remediation.