sample shows a type-IV isotherm with an H3 type hysteresis loop,
which can be ascribed to the larger secondary mesopores [41].
Fig. 8(insert) shows the pore size distribution of FST-1.0, indicating
that the FST-0.5 catalyst has a narrow mesoporosity distribution
with an average pore diameter about 4.15 nm. The specific surface
areas of all samples are summarized in Table 1. The particle sizes get
smaller with the increasing amount of irons doping. However, the
specific surface areas of FST catalysts decrease with the reducing
of particle size, which may be caused by the disorder and maldistribution
of pores. Although the specific surface areas turn smaller
with increasing Fe(III) doping, they are also very large (>184 m2/g).
The large specific surface areas can provide more activity sites, in
favor of the photocatalytic activity.