Novel hierarchical porous Fe₂O₃@GA composites for solar-Fenton catalysis of dyes

A novel hollow mesoporous Fe2O3 (HM-Fe2O3) and its graphene aerogel composite (H-Fe2O3@GA) with hierarchical porous structure were synthesized by facile solvothermal methods and applied in the photocatalytic degradation of methylene blue (MB). H-Fe2O3@GA was characterized as having excellent structural strength and uniformity. Its formation process and the photocatalytic mechanism were derived. The interaction between HM-Fe2O3 and graphene formed the hierarchical porous structure, which reduced hole-electron recombination and accelerated the cycle of Fe3+/Fe2+ on the catalyst's surface. Thus, constructing a solar-Fenton synergistic catalytic system exhibited a rapid removal ability for MB. The synergistic system is adapted to a wide pH range with low H2O2 consumption and can achieve 99.2% MB removal efficiency in 30 minutes assisted by ammonium oxalate. Reactive species scavenging and ESR experiments revealed that OH center dot and O-1(2) played a dominant role during the solar-Fenton degradation of MB. In addition, H-Fe2O3@GA can be easily recovered and regenerated given its aerogel bulk morphology, and the removal efficiency of MB by the composite was still 85.6% after five times of reuse. Therefore, in-depth research and application of H-Fe2O3@GA in dye degradation and water treatment are expected.