Visible-light Driven Photocatalytic Degradation of Rhodamine B over Ce-g-C3N4 Composite: Structure -activity Relationship Study
Abstract
Graphitic carbon nitride (g-C3N4) has emerged as a promising visible-light-responsive photocatalyst for wastewater treatment. However, its practical application is hindered by limited visible-light absorption and the rapid recombination of photogenerated charge carriers. In the present study, a cerium-modified graphitic carbon nitride composite (Ce-g-C3N4) was synthesized through a hydrothermal route to improve the photocatalytic degradation of Rhodamine B (RhB) under visible-light irradiation. The structural, morphological, and optical properties of the prepared materials were investigated using XRD, FTIR, UV-Vis spectroscopy, and SEM-EDS analyses. UV-Vis analysis revealed a reduced band gap energy of 2.59 eV for Ce-g-C3N4, indicating enhanced visible-light absorption compared with pristine g-C3N4. SEM observations showed a fragmented sheet-like morphology with a rough surface texture, which is favourable for dye adsorption and photocatalytic reactions. The effects of catalyst dosage, initial dye concentration, solution pH, and irradiation time on RhB degradation were systematically evaluated. Under the optimized conditions of 30 mg catalyst dosage, 50 ppm RhB concentration, and pH 9.5, the Ce-g-C3N4 composite achieved a maximum degradation efficiency of 89.1% within 70 min, whereas pristine g-C₃N₄ exhibited only 69.7% degradation under identical conditions. The degradation process followed pseudo-first-order kinetics with an apparent rate constant of 0.0324 min⁻¹ and a correlation coefficient (R2) of 0.9897. In addition, the photocatalyst retained 81.2% of its initial activity after five consecutive cycles, demonstrating good stability and reusability. The improved photocatalytic performance is attributed to the modification of the electronic structure and enhanced visible-light utilization induced by cerium incorporation. These findings demonstrate that Ce-g-C3N4 is an efficient and stable visible-light-responsive photocatalyst with potential applications for treating dye-contaminated wastewater.