the loss of Fe
2+ and stabilize the conversion of Fe
3+ /Fe
2+ in the photo-Fenton
reaction. Compared with Fe 2 O 3 and Fe 2 O 3 /2D-graphene (Fe 2 O 3 /GR), Fe 2 O 3 /GAs
exhibit an ultrastable, solar-driven Fenton activity over a wide pH range of 3.5–9.0
(Fig. 11.2).
11.2.6 Iron Oxide–Semiconductor
To gain better enrichment ability for pollutant as well as avoiding aggregation, inert
materials such as carbon and SiO 2 are introduced to fabricate loading or coating type
catalyst. Among them, yolk–shell (YÀS)-structured Fe 3 O 4 @void@shell composites
composed of a movable Fe 3 O 4 core and a layer of permeable shell have recently
gained increasing attention in the fields of catalysis, biology, and energy storage,
where the interior core is efficiently protected from agglomeration and accessible for
small molecules. In the context of catalysis, the cavity between the core and shell
with a flexibly tunable volume provides a nanoreactor for a variety of reactions, in
which the confined reactants may result in improved reaction rate or altered synthetic
route. On the other hand, the limited working pH range around 3 commonly
encountered by most Fenton agents has significantly obstructed the wide application.
Although the heterogeneous Fenton agent generally can be applied in less acidic
conditions, the regeneration efficiency of Fe
2+ from Fe
3+ and the oxidation potential
of hydroxyl radicals have actually both been decreased. The combination of semiconductor and Fe-containing compound has proven to be effective on reducing Fe
3+
to Fe
2+ by the photo-generated electron from semiconductor [23]. Considering the
priority of the YÀS-structured composite as a nanoreactor, it is desirable to apply it
in the ph-F process, which, however, has been retarded by the tedious preparation
process including layer-by-layer coating and removal of sacrificing layer, as well as
the underdeveloped techniques on the component-tailoring. A simple and general
synthesis technique for YÀS-structured composite is extremely desired to put
forward its application in the ph-F treatment of sewage water.
YÀS-structured Fe 3 O 4 @void@CdS nanoparticles (NPs) were synthesized
through a one-pot coating–etching process with Fe 3 O 4 @ SiO 2 as the core [24],
where the coating of an outer CdS shell from a chemical bath deposition (CBD)
process is simultaneously accompanied by the gradual etching of an inner SiO 2 shell.
The as-prepared Fe 3 O 4 @void@CdS NPs (ca. 200 nm) possess good monodispersity
and a uniform CdS shell of ca.15 nm (Fig. 11.3). This composite exhibits excellent
photo-Fenton activity toward the degradation of methylene blue (MB) in a wide pH
working range of 4.5–11 under the visible light irradiation (Fig. 11.4). A series of
control experiments demonstrate the unique YÀS structure contributes to the
enhanced activity, where the separation of holeÀelectron pair from CdS and the
reduction of Fe
2+ from Fe
3+ are mutually promoted. The similar efficiency can also
be achieved when the shell component changes to TiO 2 or CeO 2 [25], demonstrating
a general strategy for the design of robust photo-Fenton agent.
11.2 Heterogeneous Photo-Fenton Reaction
267
2+ and stabilize the conversion of Fe
3+ /Fe
2+ in the photo-Fenton
reaction. Compared with Fe 2 O 3 and Fe 2 O 3 /2D-graphene (Fe 2 O 3 /GR), Fe 2 O 3 /GAs
exhibit an ultrastable, solar-driven Fenton activity over a wide pH range of 3.5–9.0
(Fig. 11.2).
11.2.6 Iron Oxide–Semiconductor
To gain better enrichment ability for pollutant as well as avoiding aggregation, inert
materials such as carbon and SiO 2 are introduced to fabricate loading or coating type
catalyst. Among them, yolk–shell (YÀS)-structured Fe 3 O 4 @void@shell composites
composed of a movable Fe 3 O 4 core and a layer of permeable shell have recently
gained increasing attention in the fields of catalysis, biology, and energy storage,
where the interior core is efficiently protected from agglomeration and accessible for
small molecules. In the context of catalysis, the cavity between the core and shell
with a flexibly tunable volume provides a nanoreactor for a variety of reactions, in
which the confined reactants may result in improved reaction rate or altered synthetic
route. On the other hand, the limited working pH range around 3 commonly
encountered by most Fenton agents has significantly obstructed the wide application.
Although the heterogeneous Fenton agent generally can be applied in less acidic
conditions, the regeneration efficiency of Fe
2+ from Fe
3+ and the oxidation potential
of hydroxyl radicals have actually both been decreased. The combination of semiconductor and Fe-containing compound has proven to be effective on reducing Fe
3+
to Fe
2+ by the photo-generated electron from semiconductor [23]. Considering the
priority of the YÀS-structured composite as a nanoreactor, it is desirable to apply it
in the ph-F process, which, however, has been retarded by the tedious preparation
process including layer-by-layer coating and removal of sacrificing layer, as well as
the underdeveloped techniques on the component-tailoring. A simple and general
synthesis technique for YÀS-structured composite is extremely desired to put
forward its application in the ph-F treatment of sewage water.
YÀS-structured Fe 3 O 4 @void@CdS nanoparticles (NPs) were synthesized
through a one-pot coating–etching process with Fe 3 O 4 @ SiO 2 as the core [24],
where the coating of an outer CdS shell from a chemical bath deposition (CBD)
process is simultaneously accompanied by the gradual etching of an inner SiO 2 shell.
The as-prepared Fe 3 O 4 @void@CdS NPs (ca. 200 nm) possess good monodispersity
and a uniform CdS shell of ca.15 nm (Fig. 11.3). This composite exhibits excellent
photo-Fenton activity toward the degradation of methylene blue (MB) in a wide pH
working range of 4.5–11 under the visible light irradiation (Fig. 11.4). A series of
control experiments demonstrate the unique YÀS structure contributes to the
enhanced activity, where the separation of holeÀelectron pair from CdS and the
reduction of Fe
2+ from Fe
3+ are mutually promoted. The similar efficiency can also
be achieved when the shell component changes to TiO 2 or CeO 2 [25], demonstrating
a general strategy for the design of robust photo-Fenton agent.
11.2 Heterogeneous Photo-Fenton Reaction
267