In-situ controlled growth of ultrafine CeO₂ nanoparticles on reduced graphene oxides for efficient photocatalytic degradation

Nanostructured composites of metal oxides and graphene often exhibit synergistic physicochemical properties, which can be explored for applications in photocatalysis and water treatment. However, there are key issues about effective structure controls such as distributions and sizes of nanoparticles inside these composite materials. Herein, we report a green approach using hydrothermal calcination processes to in-situ grow CeO₂ nanoparticles (with their ultrafine crystalline sizes, homogeneous dispersion and controlled oxygen-vacancy) directly onto surfaces of reduced graphene oxides (rGOs). The growth process of CeO₂ NPs was characterized by in-situ TEM analysis. During the calcination process, oxygen-containing functional groups such as –OH and C[dbnd]O on the rGOs were transformed into H₂O and CO₂, which acted as oxidizing agents to react with cerium ions and produce CeO₂ nanoparticles directly onto surfaces of rGOs. Integration of ultrafine crystalline oxygen deficient CeO₂ and electrically conducting rGOs facilitated fast adsorption of reactant molecules and provided numerous active sites, which effectively achieved superior photocatalytic performance and enhanced adsorption capability for colored organic dyes of rhodamine B and methyl orange. Degradation rate of rhodamine B using the composite reached 94.7% within 120 min, and after five cycles, the degradation rate was still maintained at 87.2%, showing good stability and reusability.