SnO2 Quantum Dot-Decorated g-C3N4 Ultrathin Nanosheets: A Dual-Function Photocatalyst for Pollutant Degradation and Hydrogen Evolution

The development of advanced functional composite materials for degrading industrial pollutants and achieving photocatalytic hydrogen (H2) production using abundant solar energy is pivotal in new and renewable energy research. This study presents the synthesis of a nanostructure comprising SnO2 quantum dots (QDs) randomly dispersed on the surface of graphitic carbon nitride (C3N4) nanosheets (Sn-C3N4), achieved through the thermal decomposition of melamine and a tin precursor. The synthesized materials were extensively characterized using various analytical techniques, with HRTEM analysis confirming the strong interaction between SnO2 QDs and C3N4. The influence of SnO2 QDs on the nanocomposite’s photocatalytic performance was evaluated, particularly regarding H2 production and the degradation of crystal violet (CV) dye under simulated solar-light irradiation. The SnO2-loaded C3N4 nanostructure exhibited a marked enhancement in photocatalytic activity, attributed to the synergistic effects of the quantum-sized SnO2 nanoparticles. The optimized photocatalyst, 3-Sn-C3N4, demonstrated superior photocatalytic efficiency, achieving 95% degradation of CV dye within 45 min under simulated sunlight, significantly outperforming bare C3N4. Furthermore, the 3-Sn-C3N4 nanostructure attained the highest H2 yield of 1305.4 μmol/h/g, a 4.6-fold increase compared with bare C3N4 (281 μmol/h/g). Enhanced photocatalytic performance was corroborated by photocurrent and EIS studies, which highlighted reduced charge carrier recombination as a critical factor in the improved activity. The underlying photocatalytic mechanisms were also examined.