From Pollutant Removal to Renewable Energy: MoS₂-Enhanced P25-Graphene Photocatalysts for Malathion Degradation and H₂ Evolution

The increasing contamination of water sources by pesticides, particularly malathion, poses a challenge for conventional treatment methods, while the global energy crisis highlights the need for sustainable alternatives such as hydrogen. Photocatalytic water splitting is a promising method for hydrogen production, but its efficiency is hindered by poor charge separation, limited light absorption, and slow reaction rates. This study explores TiO₂-based nanocomposites, specifically P25-reduced graphene oxide (rGO) modified with varying MoS₂ loadings (1%, 3%, 5%, and 10%), to simultaneously enhance pollutant degradation and hydrogen evolution. rGO improves charge carrier separation, increases surface area, and facilitates electron transport, while MoS₂ serves as a co-catalyst that promotes charge transfer and provides active sites for hydrogen evolution reactions. The nanocomposites were synthesized and characterized by X-ray diffraction (XRD), Raman spectroscopy, transmission electron microscopy (TEM), UV-Vis diffuse reflectance spectroscopy (DRS), and photoluminescence (PL) to evaluate structural, morphological, and optical properties. Photocatalytic degradation of malathion was analyzed under simulated solar irradiation using UV-Vis spectroscopy and gas chromatography-mass spectrometry (GC-MS), while hydrogen production was assessed in an aqueous suspension with a sacrificial agent, with hydrogen evolution quantified via gas chromatography (GC-TCD). The results demonstrated that the synergistic incorporation of rGO and MoS₂ into P25 TiO₂ significantly improved photocatalytic performance, where rGO enhanced charge separation and electrical conductivity, while MoS₂ acted as an electron acceptor and catalytic site for hydrogen generation. Under optimized conditions, nearly 100% degradation of malathion was achieved within 2 hours, and hydrogen evolution rates approached 6000 µmol g⁻¹ h⁻¹. An optimal MoS₂ loading maximized efficiency, though excessive amounts led to charge recombination. This study highlights the potential of P25-rGO-MoS₂ nanocomposites for scalable applications in water treatment and hydrogen production, contributing to sustainable and cost-effective photocatalytic technologies.