Figure 1 . (a) Schematic illustration of synthesis of
ZnY@MnOx /XPCNFs sorbent. (b) Schematic
illustration of the surface areas of CNFs and PCNFs. (c) Structural
parameters of pristine CNFs, 0PCNFs and 24PCNFs. (d) Loading contents of
Mn in sorbents MnOx /CNFs,
MnOx /0PCNFs, MnOx /24PCNFs
and Zn@MnOx /24PCNFs.
First, the surface area enlargement of pristine CNFs and PCNFs is
theoretically studied to rationally guide structural tuning of CNFs
supporter (Figure. 1a). SiO2 nanospheres were introduced
into the electrospun PAN matrix as hard template for the purpose of
expanding the surface area and attachment sites for metal oxides.
Herein, as shown in Figure. 1b, assuming the single nanofiber in
pristine CNFs is a cylinder with diameter (d) ≈ 0.1 mm and height ≈ 0.1
mm, the lateral area SO of the single nanofiber is
0.1256 mm2. In the meantime, the diameter
(dP) of the hollow carbon shell derived from the etching
of SiO2 sphere is assumed equal to d of the cylinder.
Based on the above hypothesis, after the introduction and etching of
SiO2, the ST and SP of
the enlarged single nanofiber calculated are 0.2405 and 0.2856
mm2, respectively, which are 1.9 and 2.3 times higher
than that of the pristine CNFs. Theoretically, the highest area of
enlarged single nanofiber can reach up to 0.3556 mm2,
more than 2.8 times higher than that of the pristine CNFs (Figure. S1).
According to the models established and the calculations, our hypothesis
is beneficial for an enlarged and expanded surface area of porous CNFs.
Besides, N2 adsorption-desorption was applied to
analysis the structural parameters of the modified PCNFs (Figure. 1c).
The strategy employed successfully enlarges the specific surface area
and total pore volume from 51.765 m2g-1 and 0.082 cm3g-1 to 250.684 m2g-1 and 0.228 cm3g-1, which realizes amplifications of 483% and 278%,
respectively. Furthermore, the pristine CNFs, PCNFs were processed
through activation oxidation in KMnO4 solution for the
adherent of MnOx . ICP characterization verified
the same trend in Mn2+ content as structural
parameters display. The Mn2+ content in sorbent
MnOx /24PCNFs is 17.8%, while it’s only 5.5% in
sorbent with pristine CNFs as supporter. According to the above results,
it can be seen that this unique desulfurization sorbent using the
surface area enlarged PCNFs as supporter could provide expanded surface
area and a plenty of attachment sites for the loading of active
components. Besides, the three dimensional opening structure of the
modified CNFs will improve the mass transfer and ion diffusion rate of
the corresponding desulfurization sorbent.