Combined Effect of Sonication and Electron Beam Irradiation on the Photocatalytic Organic Dye Decomposition Efficiency of Graphitic Carbon Nitride

The photocatalytic efficiency of graphitic carbon nitride (g-C3N4) for the decomposition of aqueous rhodamine B (RhB) was investigated. To examine the combined effects of sonication and electron beam (EB) irradiation on the photocatalytic efficiency, g-C3N4 was sonicated in 1,3-butanediol and subsequently irradiated with EB. The photocatalytic efficiency was improved by the low-dose EB irradiation due to the generation of structural defects that acted as active reaction sites. Sonication before EB irradiation induced mild exfoliation and further improved photocatalytic efficiency. Prolonged sonication enhanced this improvement, primarily by increasing the specific surface area of g-C3N4. The positive effect of sonication was more remarkable for g-C3N4 irradiated with low-dose EB than for g-C3N4 irradiated with higher-dose EB. The photocatalytic RhB decomposition rate measured for g-C3N4 sonicated for 480 min and irradiated at 200 kGy was approximately 6.8 times higher than that measured for the untreated g-C3N4. The difference between the sonication effects can be ascribed to the electrostatic interactions and the resultant agglomeration of the g-C3N4 particles after EB irradiation. High-dose EB irradiation caused electrification followed by coarsening of the particles, whereas low-dose EB irradiation did not produce these results and led to positive effects due to the EB-induced g-C3N4 structural alteration.