Characterizing Carbon Ring-C₃N₄ Nanosheets as a Light-Harvesting and Charge Carrier Transfer Agent: Photodegradation of Methylene Blue and Photoconversion of CO₂ to CH₄ as Case Studies

Carbon ring–carbon nitride nanosheets (C ring -C 3 N 4 ) were synthesized by using glucose as the carbon source. The C ring -C 3 N 4 was characterized in order to check its ability in harvesting light in the visible region and transferring the charge carriers. Degradation of methylene blue (MB) after being adsorbed on the surface of the photocatalyst and also the photoreduction of CO 2 to CH 4 were studied for proving applicability of C ring -C 3 N 4 in solving pollution problem and fuel crisis. The results were compared with those of bulk C 3 N 4 . The results showed that the adsorption process was fit to the Langmuir model (with a Q max of 130 mg/g) with a kinetic of the pseudo second order (with a Q e.cal of 180 mg/g). The photodegradation rate constant of MB proved that C ring -C 3 N 4 nanosheets had a catalytic activity (0.0616/h) almost 26 times more than g-C 3 N 4 in the presence of light. At a melamine/glucose mass ratio of 1000/50, the photoconversion rate of CO 2 to CH 4 (16.24 μmol/g·h) achieved nearly 24 times greater when compared to g-C 3 N 4 and was comparable with the photodegradation rate of MB. In the presence of light, it was observed that the reduction of carbon dioxide to methane was via a process of eight electrons which predominated over the production of carbon monoxide with a process of two electrons. The C ring -C 3 N 4 synergistically extended lifetime and photocarrier diffusion length. This photocatalyst can be effectively utilized in sustainable solar-to-fuel conversion processes as well as in environmental pollutant remediation.