This study reports on successful synthesis of carbon
dots (CDs),
nitrogen-doped zinc oxide (N-ZnO), and N-ZnO/CD nanocomposites as
photocatalysts for degradation of methylene blue. The first part was
the synthesis of CDs utilizing a precursor from soybean and ethylenediamine
as a dopant by a hydrothermal method. The second part was the synthesis
of N-ZnO with urea as the nitrogen dopant carried out by a calcination
method in a furnace at 500 °C for 2 h in an N2 atmosphere
(5 °C min–1). The third part was
the synthesis of N-ZnO/CD nanocomposites. The characteristics of CDs,
N-ZnO, and N-ZnO/CD nanocomposites were analyzed through Fourier transform
infrared (FTIR), UV–vis absorbance, photoluminescence (PL),
high-resolution transmission electron microscopy (HR-TEM), X-ray diffraction
(XRD), thermal gravimetry analysis (TGA), field-emission scanning
electron microscopy energy-dispersive spectroscopy (FESEM EDS), X-ray
photoelectron spectroscopy (XPS), and Brunauer–Emmett–Teller
(BET) analysis. Based on the HR-TEM analysis, the CDs had a spherical
shape with an average particle size of 4.249 nm. Meanwhile, based
on the XRD and HR-TEM characterization, the N-ZnO and N-ZnO/CD nanocomposites
have wurtzite hexagonal structures. The materials of N-ZnO and N-ZnO/CD
show increased adsorption in the visible light region and low energy
gap E
g. The E
g values of N-ZnO and N-ZnO/CDs were found to be 2.95 and 2.81 eV,
respectively, whereas the surface area (S
BET) values 3.827 m2 g–1 (N-ZnO) and 3.757
m2 g–1(N-ZnO/CDs) belonged to the microporous
structure. In the last part, the photocatalysts of CDs, N-ZnO, and
N-ZnO/CD nanocomposites were used for degradation of MB (10 ppm) under
UV-B light irradiation pH = 7.04 (neutral) for 60 min at room temperature.
The N-ZnO/CD nanocomposites showed a photodegradation efficiency of
83.4% with a kinetic rate of 0.0299 min–1 higher
than N-ZnO and CDs. The XRD analysis and FESEM EDS of the N-ZnO/CDs
before and after three cycles confirm the stability of the photocatalyst
with an MB degradation of 58.2%. These results have clearly shown
that the N-ZnO/CD nanocomposites could be used as an ideal photocatalytic
material for the decolorization of organic compounds in wastewater.
Research about the performance of Graphite/N-Graphene and Graphene/N-Graphene as the cathode of primary used modified Hummers and impregnation methods was carried out. Characterization of materials was characterized by using XRD, FTIR, SEM-EDX and Conductometry, respectively. XRD data show that N atoms were well be deposited on Graphene to form N-Graphene, it was indicated by the weak peak was appear at 2θ = 26.16º. This data was consistent with EDX data where N atoms existed on N-Graphene (2.72 %). FTIR data broad definitely confirm that there is an interaction between C and N (peak at 1396 cm -1 ). The conductivity data showed that N-Graphene has higher conductivity value (1157.32 µS/cm). Meanwhile, the conductivity of Graphite/N-Graphene (1:2) is higher (350.20 µS/cm) compared to the Graphite/N-Graphene (2:1) (102.70 µS/cm) and conductivity of Graphene/N-Graphene (1:2) is higher (969.33 µS/cm) compared to the Graphene/N-Graphene (2:1) (878.18 µS/cm). All data prove that N-Graphene may increase the performance of Graphite/N-Graphene and Graphene/N-Graphene on cathode's primary battery.
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