Estudo de geração de vapor de água mediado por folhas de grafeno oxidado e grafeno oxidado reduzido

Abstract

This work investigates photothermal conversion and steam generation in nanofluids based on graphene oxide (GO) and reduced graphene oxide (rGO), obtained via reduction with L-ascorbic acid (ALA) and palladium chloride (PdCl2). The study focused on the correlation between modifications in the material's electronic and morphological structure and its thermal transport and optical absorption properties. Characterization via electron microscopy, Raman spectroscopy, and UV–Vis indicated that PdCl2 promotes the restoration of the graphitic lattice and sheet stacking, whereas ALA tends to keep the sheets more separated, resulting in a less compact morphology. Thermal Lens measurements revealed non-monotonic behavior of thermal diffusivity regarding the dispersed phase concentration: a reduction in diffusivity was observed at low concentrations relative to the base fluid, followed by an increase at higher concentrations. Although the exact causes of this behavior require further investigation, the data suggest a complex interaction between heat transport in the solvent and the presence of the nanostructures. In evaporation tests, the highest efficiencies (up to ∼70%) were not associated solely with the highest degree of structural ordering, but rather with hybrid samples combining high optical absorption with moderate thermal diffusivity, which favors the localization of thermal energy at the liquid-vapor interface. The results demonstrate that controlling aggregation and optical properties is crucial for optimizing solar-thermal energy conversion systems.