These microporesare formed by the release of non-carbon components such as N and
O on carbonization, and due to the use of KOH as an activating
agent. The activated carbons have comparable specific surface
areas (SBET) in the range of 1636–1957 m2 g1 and pore volumes
about 0.51–0.83 cm3 g1 (Table 1). X-ray diffraction (XRD) for all
samples show a broad peak diffraction present at about 2h = 26,
that suggests that they have little crystalline structure (Fig. S3).
Activated carbon materials were also characterized using (FTIR)
spectroscopy (Fig. 3). The appearance of a broad band around
3430 cm1 is attributed to the O–H stretching vibration of hydroxyl
groups and (N–H) stretching vibration of amine groups. The
positions of hydrogen bonded OH groups are usually in the range
of 3200–3650 cm1 for alcohols and phenols. The existence of band
at 1590 cm1 indicates the presence of oxygenated functionalities
in non-conjugated and conjugated systems [38]. The broad band at
978–1210 cm1 is attributed to vinyl group (@C–H) in-plane and
out-of-plane vibration, and maybe related to (C–O) and (C–N)
bonds [39]. Thus the existence of these non-carbon elements and
functional groups enhances the adsorption of gases [40].
The XPS spectra (Figs. 4A and S4) clearly show the existence and
chemical characteristics of carbon, oxygen and nitrogen in the
samples. The percentage of various elements in the sample is calculated
after fitting the spectra identically to each element. The
XPS data indicate that the material contains mainly carbon, oxygen
and a small amount of nitrogen. The three peaks observed in C1s
spectrum for GSK1-700 sample correspond to C@C (284.9 eV),
C–O (286.2 eV) and C@O (288.6 eV). Whereas, there are two peaks
in the C1s spectrum located at 285 and 286.7 eV, which attribute
to C@C and, C–O respectively for GSK0.5-700 and GSK2-700
as shown in (Fig. S5).
It is