Z-Scheme Photocatalytic Mechanism in Inorganic-Organic rGO Mediated SnO₂/CeTiO₄ Nanocomposites for Efficient Degradation of Organic Pollutants

The present work here reports hydrothermal synthesis of rGO/SnO₂/CeTiO₄ nanocomposites (RSC NCs). Structural characterization based on crystal size was 10.6 nm and direct band gap energy of 2.92 eV, indicating the material’s potential as a good sunlight-driven photocatalyst. FESEM revealed agglomerated RSC NCs and rGO with a stacked layer structure. TEM also indicated the homogeneous distribution of SnO₂ and CeTiO₄ nanoparticles across the surface of the rGO. The photocatalytic performance was evaluated by degrading methylene blue (MB) and methyl orange (MO) dyes, achieving significant removal efficiencies of 96.22% and 92.19%, respectively, at an initial concentration of 50 ppm after 90 min of sunlight exposure. The degradation followed pseudo-first-order kinetics with rate constants (k) varying from 0.00258 to 0.03641 min^{− 1} for MB and from 0.00227 to 0.02133 min^{− 1} for MO. Hydroxyl radicals (•) and superoxide anions were found to be the active species responsible for the degradation. The material was also highly reusable and provided high efficiency for up to five cycles. The mixed dye solution of MB and MO also validated RSC NCs photocatalytic activity under sunlight. These results indicate the high performance of RSC NCs with higher degradation rates and excellent stability that render them as a promising and sustainable material for the cleanup of environmental pollutants.