Optimizing thermal reduction of graphene oxide for enhanced solar-driven water purification using rGO-TiO₂ nanocomposites

In this study, we optimized the thermal reduction of graphene oxide (GO) to fabricate reduced graphene oxide-titanium dioxide (rGO-TiO₂) nanocomposites for solar-driven water purification. Conventional reduction methods often lack control over functional group removal, resulting in inconsistent photocatalytic performance. We employed in situ thermal reduction under a nitrogen atmosphere, identifying 240 °C as the optimal temperature via thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The process effectively removed oxygen-containing functional groups, as confirmed by X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy, restoring a graphene-like structure. Scanning electron microscopy (SEM) revealed morphological changes in GO and rGO during the reduction process. UV–vis spectroscopy and XPS showed improved structural and optical properties of rGO-TiO₂ nanocomposites. Photocatalytic tests under natural sunlight in Al-Kharj City, Saudi Arabia, demonstrated 99 % degradation of methylene blue within 90 min, outperforming pristine TiO₂ (86 %). This enhancement is attributed to improved light absorption, reduced charge recombination, and higher surface area. The findings provide a scalable, eco-friendly approach for global water purification challenges.