Figure 2 a Low and b high-magnification SEM
images of ZnCo2O4; c SEM images
of Ag3PO4; d SEM images of
ZnCo2O4/Ag3PO4;e TEM image of
ZnCo2O4/Ag3PO4;f HRTEM image of
ZnCo2O4/Ag3PO4and g SAED pattern of
ZnCo2O4/Ag3PO4.
Fig. 2a shows the spherical ZnCo2O4successfully synthesized by the microwave-assisted method with a
diameter range of 3–8 μm. Fig. 2b shows the structure of a single
ZnCo2O4 microsphere, which can be seen
from the figure as a stack of nanosheets. Fig. 2c shows
Ag3PO4 crystals with a regular
hexahedral structure and a particle size range of 0.4–1 μm. Fig. 2d is
an SEM image of the composite
ZnCo2O4/Ag3PO4.
It can be seen from the figure that the particle size range of
ZnCo2O4/Ag3PO4is also 0.4–1 μm, which is caused by the recrystallization of
ZnCo2O4 and deposition on
Ag3PO4 during the synthesis process. To
further observe the morphology of
ZnCo2O4/Ag3PO4,
Fig. 2e shows the TEM image of
ZnCo2O4/Ag3PO4,
from which it can be seen that the recrystallized
ZnCo2O4 is attached to the
Ag3PO4 crystal surface. Fig. 2f shows
the HRTEM image of
ZnCo2O4/Ag3PO4,
which further verifies that the recrystallized
ZnCo2O4 is successfully attached to the
Ag3PO4 crystal surface, and the lattice
spacing d is 0.244 and 0.269 nm for
ZnCo2O4 and
Ag3PO4, corresponding to the (220) and
(210) crystal planes of ZnCo2O4 and
Ag3PO4, respectively. Fig. 2g shows the
SAED plot of
ZnCo2O4/Ag3PO4,
in which the bright diffraction rings of
ZnCo2O4/Ag3PO4can be seen, indicating that it is polycrystalline. In addition, the
lattice distances of 0.244 nm and 0.269 nm for the two crystal planes
can be clearly seen in Fig. 2g, which is in agreement with the results
of HRTEM plots. In summary, it can be clearly seen that the composite
catalyst
ZnCo2O4/Ag3PO4is formed by loading the recrystallized
ZnCo2O4 onto the
Ag3PO4 crystal surface.