limits the reaction rate of Fenton process which is the control step and key procedure
to enhance the catalytic capacity of Fe 3 O 4 NPs [57–60].
In order to overcome these drawbacks, methods like immobilizing Fe 3 O 4
nanoparticles onto support materials or encapsulating them within thin protective
layer to prevent their aggregation and electron acceptors are utilized to accelerate the
electron transfer. Naturally, carbon materials, especially graphene, attract the focus
of chemical researchers again, which not only can be supporters to anchor
nanoparticles but also acceptors to receive electrons. Several researches have
reported that the in situ growth of Fe 3 O 4 NPs onto graphene can not only effectively
inhibit the aggregation of magnetite but also enable them to contact with each other
intimately, and such structure favored the transmission of photoactive electrons from
Fe 3 O 4 NPs to graphene. The magnetite nanoparticles are dispersed on the GO
(or rGO) sheets and immobilized by ferric or ferrous ions bonded with oxygencontaining functional group as crystal nucleuses, which will be the active sites for
catalysis. Herein, the surface area of magnetite is enlarged and the surface energyderived agglomeration of nanosized particles is prevented by graphene sheets. In
return, Fe 3 O 4 NPs with certain size can avoid accumulation of adjacent graphene
sheets. Zhou et al. [61] have successfully synthesized GO-Fe 3 O 4 composite through
in situ depositing cubic-phase Fe 3 O 4 on the surface of GO and proved the existence
of the C–O–Fe coordination bond by FTIR. The composite showed excellent
performance on photocatalytic degrading organic contaminant isatin. In another
study, Qiu et al. [62] reported a simple Stöber-like method without additional
reductants and organic surfactants on the synthesis of rGO–Fe 3 O 4 nanocomposite,
which was environmental friendly and suitable for mass production. The Fe 3 O 4 NPs
were ultra-dispersed on the graphene sheets during the in situ growth process and the
particle sizes were well controlled at an extremely small value (3–8 nm), which was
clearly seen in Fig. 10.5. The results of Photo-Fenton experiments to degrade methyl
orange, methylene blue, and Rhodamine B were satisfactory due to the high surface
area and fast electron transfer.
The graphene content in the magnetite-based composites also plays one of the
decisive factors for the performance of photocatalyst. There is no doubt that the
graphene content of the composite has an optimal value for the sake of the highest
photocatalytic activity similar to combination with Fe 2 O 3 above. Zubir et al. [63]
have found that the beneficial intercalation of GO within Fe 3 O 4 nanoparticles was
10 wt% after a series of experiments using composites with different weight ratio of
GO to degrade organic compounds, which showed 20% higher degradation rate of
Acid Orange 7 than that of bare Fe 3 O 4 nanoparticles, as well (Fig. 10.6a). This can
be explained that at high GO loading, stacking of the graphene sheets may happen
through the π-π interactions which correspond to the van der Waals and hydrophobic
fields around the carbon basal plane of GO sheets. Therefore, the aggregation of
Fe 3 O 4 NPs on the exterior surface of GO stacking might hamper the effective
diffusion and contact between the reactants toward the active sites and decrease
the ample formation of hydroxyl radicals to decompose AO7 during the reaction.
The pH range was extended to nearly neutral condition and the cyclicity of the
composite was perfect as shown in Fig. 10.6b and 6c. Likewise, Yu et al. [64]
10.2 Graphene/Iron (Hydr)oxide Composites Applied in Fenton Reaction
249
to enhance the catalytic capacity of Fe 3 O 4 NPs [57–60].
In order to overcome these drawbacks, methods like immobilizing Fe 3 O 4
nanoparticles onto support materials or encapsulating them within thin protective
layer to prevent their aggregation and electron acceptors are utilized to accelerate the
electron transfer. Naturally, carbon materials, especially graphene, attract the focus
of chemical researchers again, which not only can be supporters to anchor
nanoparticles but also acceptors to receive electrons. Several researches have
reported that the in situ growth of Fe 3 O 4 NPs onto graphene can not only effectively
inhibit the aggregation of magnetite but also enable them to contact with each other
intimately, and such structure favored the transmission of photoactive electrons from
Fe 3 O 4 NPs to graphene. The magnetite nanoparticles are dispersed on the GO
(or rGO) sheets and immobilized by ferric or ferrous ions bonded with oxygencontaining functional group as crystal nucleuses, which will be the active sites for
catalysis. Herein, the surface area of magnetite is enlarged and the surface energyderived agglomeration of nanosized particles is prevented by graphene sheets. In
return, Fe 3 O 4 NPs with certain size can avoid accumulation of adjacent graphene
sheets. Zhou et al. [61] have successfully synthesized GO-Fe 3 O 4 composite through
in situ depositing cubic-phase Fe 3 O 4 on the surface of GO and proved the existence
of the C–O–Fe coordination bond by FTIR. The composite showed excellent
performance on photocatalytic degrading organic contaminant isatin. In another
study, Qiu et al. [62] reported a simple Stöber-like method without additional
reductants and organic surfactants on the synthesis of rGO–Fe 3 O 4 nanocomposite,
which was environmental friendly and suitable for mass production. The Fe 3 O 4 NPs
were ultra-dispersed on the graphene sheets during the in situ growth process and the
particle sizes were well controlled at an extremely small value (3–8 nm), which was
clearly seen in Fig. 10.5. The results of Photo-Fenton experiments to degrade methyl
orange, methylene blue, and Rhodamine B were satisfactory due to the high surface
area and fast electron transfer.
The graphene content in the magnetite-based composites also plays one of the
decisive factors for the performance of photocatalyst. There is no doubt that the
graphene content of the composite has an optimal value for the sake of the highest
photocatalytic activity similar to combination with Fe 2 O 3 above. Zubir et al. [63]
have found that the beneficial intercalation of GO within Fe 3 O 4 nanoparticles was
10 wt% after a series of experiments using composites with different weight ratio of
GO to degrade organic compounds, which showed 20% higher degradation rate of
Acid Orange 7 than that of bare Fe 3 O 4 nanoparticles, as well (Fig. 10.6a). This can
be explained that at high GO loading, stacking of the graphene sheets may happen
through the π-π interactions which correspond to the van der Waals and hydrophobic
fields around the carbon basal plane of GO sheets. Therefore, the aggregation of
Fe 3 O 4 NPs on the exterior surface of GO stacking might hamper the effective
diffusion and contact between the reactants toward the active sites and decrease
the ample formation of hydroxyl radicals to decompose AO7 during the reaction.
The pH range was extended to nearly neutral condition and the cyclicity of the
composite was perfect as shown in Fig. 10.6b and 6c. Likewise, Yu et al. [64]
10.2 Graphene/Iron (Hydr)oxide Composites Applied in Fenton Reaction
249