**3.3 Chemical analysis**

The surface chemical composition of the prepared samples was confirmed by the FTIR, EDAX, Elemental mapping, and XPS analyses.

#### *3.3.1 FTIR analysis*

The vibrational bands of the prepared samples were analyzed by FTIR analysis (using a Bruker model Tensor 27 instrument) and the results are shown in **Figure 5a**. All the spectra, exhibit a strong band at 3700 to 3000 cm<sup>1</sup> which could be ascribed to the vibration of surface adsorbed water molecules and in the case of LDH plates, it is due to the formation of interlayer water molecules. Furthermore, several bands were observed in the 1200–1650 cm<sup>1</sup> region, which is assigned to the characteristic stretching modes of CdN heterocycles [39]. The absorption bands at 1620 cm<sup>1</sup> are associated with the C]O of the carboxylate groups. The occurrence of the feeble band at 1631 and 1643 cm<sup>1</sup> can be ascribed to the bending frequency and OdH asymmetric stretching vibration of the water molecules, respectively [40, 41]. The characteristic absorption band of ZnO samples was observed at 595 cm<sup>1</sup> , which is related to the metal-oxygen stretching vibration. The absorption

bands at 653 cm<sup>1</sup> could be owed to the MdOdM lattice vibrations of the hexagonal sheets [42]. The successful intercalation of g-C3N4 and ZnO with Mg-Al LDH were observed from the presence of their corresponding bonds, in the FTIR results.

*(a) FTIR spectra for as prepared samples (b) EDX spectra of MgAl LDH and g-C3N4\ZnO\Mg-Al LDH ternary nanocomposite and (c) mapping analysis of g-C3N4\ZnO\Mg-Al LDH ternary nanocomposite [34].*

*LDH Ternary Nanocomposites: g-C3N4 Intercalated ZnO\Mg-Al for Superior…*

*DOI: http://dx.doi.org/10.5772/intechopen.89325*

nanocomposite by EDX analysis (carried out using a JEOL Model JED 2300). From the EDX results, it could be able to observe the high percentages of O, Mg and Al elements, present in the as-prepared samples and no other impurities were observed. The elemental mapping of Mg-Al LDH and g-C3N4\ZnO\Mg-Al LDH ternary nanocomposite were presented in **Figure 5c**, which indicates the even

XPS analysis was used to investigate the surface chemical composition of the prepared ternary nanocomposite and the obtained results were shown in **Figure 6**. The survey spectra show that the prepared sample is contain Mg, Al, Zn, O, C and N elements which creating peaks corresponding to Mg 1s, Al 2p, Zn 2p, O 1s, C 1s, and N 1s positions, respectively (**Figure 6A**). The high-resolution spectra of individual elements are presented in **Figure 6B**. The Mg2+ species are observed by the presence of Mg 2p, Mg 2s, Mg KLL, and Mg 1s state corresponding to the binding energies of 52.8, 90.8, 306.8, 351.8 and 1302.8 eV, respectively [43]. The high-resolution spectra of Mg 1s are fitted with three segments associating to the binding energies of 1307, 1308 and 1308.8 eV, which are ascribed to Mg, Mg-CO3 and MgO [44, 45]. The Al attributed to the two states such as Al 2p and Al 1s and the characteristic

**Figure 5b** shows the observed elemental composition of the ternary

distribution of the observed elements across the sample.

*3.3.2 EDX analysis*

**Figure 5.**

*3.3.3 XPS analysis*

**111**

#### **Figure 4.**

*Morphology analysis: FE-SEM images of (a) Mg-Al LDH, (b) g-C3N4, (c) g-C3N4\ZnO\Mg-Al LDH ternary nanocomposite and HRTEM images of (d) Mg-Al LDH, (e) g-C3N4\ZnO\Mg-Al LDH ternary nanocomposite, (f) SAED pattern of ternary nanocomposite [34].*

*LDH Ternary Nanocomposites: g-C3N4 Intercalated ZnO\Mg-Al for Superior… DOI: http://dx.doi.org/10.5772/intechopen.89325*

**Figure 5.**

acquired from FE-SEM investigation. Some dull spots showed up on the outside of the LDH, demonstrating that the ZnO nanoparticles are well attached on the LDH surfaces. Some dark spots appeared on the surface of the LDH, indicating that the ZnO nanoparticles are well attached to the surface of the as-prepared LDH. The 2D\2D ternary nanocomposites assembly was successfully obtained, and by arresting the ZnO\Mg-Al LDH sheets with g-C3N4 sheets, the formation of the 2D\2D ternary nanocomposite was possible. Surprisingly, after the formation of the ternary nanocomposite, the LDH loose its horizontal stacking arrangements and started aligning vertically on the surface of the g-C3N4 nanosheets. These types of arrangements provide a more active surface for the prepared photocatalysts.

The surface chemical composition of the prepared samples was confirmed by the

The vibrational bands of the prepared samples were analyzed by FTIR analysis

, which is related to the metal-oxygen stretching vibration. The absorption

*Morphology analysis: FE-SEM images of (a) Mg-Al LDH, (b) g-C3N4, (c) g-C3N4\ZnO\Mg-Al LDH ternary*

*nanocomposite and HRTEM images of (d) Mg-Al LDH, (e) g-C3N4\ZnO\Mg-Al LDH ternary*

*nanocomposite, (f) SAED pattern of ternary nanocomposite [34].*

**Figure 5a**. All the spectra, exhibit a strong band at 3700 to 3000 cm<sup>1</sup> which could be ascribed to the vibration of surface adsorbed water molecules and in the case of LDH plates, it is due to the formation of interlayer water molecules. Furthermore, several bands were observed in the 1200–1650 cm<sup>1</sup> region, which is assigned to the characteristic stretching modes of CdN heterocycles [39]. The absorption bands at 1620 cm<sup>1</sup> are associated with the C]O of the carboxylate groups. The occurrence of the feeble band at 1631 and 1643 cm<sup>1</sup> can be ascribed to the bending frequency and OdH asymmetric stretching vibration of the water molecules, respectively [40, 41]. The characteristic absorption band of ZnO samples was observed at

(using a Bruker model Tensor 27 instrument) and the results are shown in

**3.3 Chemical analysis**

*3.3.1 FTIR analysis*

595 cm<sup>1</sup>

**Figure 4.**

**110**

FTIR, EDAX, Elemental mapping, and XPS analyses.

*Assorted Dimensional Reconfigurable Materials*

*(a) FTIR spectra for as prepared samples (b) EDX spectra of MgAl LDH and g-C3N4\ZnO\Mg-Al LDH ternary nanocomposite and (c) mapping analysis of g-C3N4\ZnO\Mg-Al LDH ternary nanocomposite [34].*

bands at 653 cm<sup>1</sup> could be owed to the MdOdM lattice vibrations of the hexagonal sheets [42]. The successful intercalation of g-C3N4 and ZnO with Mg-Al LDH were observed from the presence of their corresponding bonds, in the FTIR results.

#### *3.3.2 EDX analysis*

**Figure 5b** shows the observed elemental composition of the ternary nanocomposite by EDX analysis (carried out using a JEOL Model JED 2300). From the EDX results, it could be able to observe the high percentages of O, Mg and Al elements, present in the as-prepared samples and no other impurities were observed. The elemental mapping of Mg-Al LDH and g-C3N4\ZnO\Mg-Al LDH ternary nanocomposite were presented in **Figure 5c**, which indicates the even distribution of the observed elements across the sample.

#### *3.3.3 XPS analysis*

XPS analysis was used to investigate the surface chemical composition of the prepared ternary nanocomposite and the obtained results were shown in **Figure 6**. The survey spectra show that the prepared sample is contain Mg, Al, Zn, O, C and N elements which creating peaks corresponding to Mg 1s, Al 2p, Zn 2p, O 1s, C 1s, and N 1s positions, respectively (**Figure 6A**). The high-resolution spectra of individual elements are presented in **Figure 6B**. The Mg2+ species are observed by the presence of Mg 2p, Mg 2s, Mg KLL, and Mg 1s state corresponding to the binding energies of 52.8, 90.8, 306.8, 351.8 and 1302.8 eV, respectively [43]. The high-resolution spectra of Mg 1s are fitted with three segments associating to the binding energies of 1307, 1308 and 1308.8 eV, which are ascribed to Mg, Mg-CO3 and MgO [44, 45]. The Al attributed to the two states such as Al 2p and Al 1s and the characteristic

#### **Figure 6.**

*XPS spectra of C3N4\ZnO\Mg-Al LDH ternary nanocomposite: (A) survey spectra and (B) high resolution XPS spectra of (a) Mg 1s (b) Al 2p (c) Zn 2p (d) O 1s (e) C 1s (f)N 1s [34].*

peak were observed at 76.8 and 120.8 eV. The occurrence of Zn is seen from the two Zn 2p states as Zn 2P3\2 and Zn 2P1\2 corresponding to 1020.8 and 1043.8 eV respectively. It additionally uncovers that the Zn is available just in 2+ oxidation state which affirms the conceivable bonding between Zn and O [10]. The oxygen O 1s is deconvoluted into three peaks corresponding to the O<sup>2</sup> at 532.2 eV, OH species at 533 eV and CdOdO at 536 eV, respectively [46]. In over-all, the inferior binding vitality of O 1s peaks emerges from the bond between O2 and Zn2+ metal ions. The C 1s spectra can be deconvoluted into dual contributions such as 284.4 and 289 eV, assigned to the occurrence of sp<sup>2</sup> hybridized carbon atoms and C]*N*dC bonding [47], respectively. The N 1s spectra can be tailored into three basic peaks with the binding energies of 402, 404.1 and 405 eV, which are attributable to the binding of CdN, CdNdC, and NdN respectively [20]. Henceforth, the above observations affirm the formation of g-C3N4\ZnO\Mg-Al LDH ternary nanocomposite and the XPS results are in good agreement with FTIR, EDX and mapping analyses.

g-C3N4, g-C3N4\ZnO\Mg-Al LDH ternary nanocomposite, respectively. The UV-Vis absorption results show the considerable enhancement in the visible light absorption and it is because of this reason, an enhancement in the photocatalytic performance of the as-prepared photocatalyst is observed (discussed in the

*and (b) ZnO (c) g-C3N4 (d) g-C3N4\ZnO\Mg-Al LDH ternary nanocomposite) [34].*

*LDH Ternary Nanocomposites: g-C3N4 Intercalated ZnO\Mg-Al for Superior…*

*DOI: http://dx.doi.org/10.5772/intechopen.89325*

*(A) UV-Vis absorption spectra (B) Tauc's plots and (C) PL spectra of the prepared samples ((a) Mg-Al LDH*

The emission spectrum is produced because of recombination of the charge carriers and it provides hints about the proficiency of charge carrier transformation, trapping, and separation of the photo generated electrons-holes pairs. The strong PL emission profile usually indicates the quick recombination of electron-hole pairs

**Figure 7C** shows the PL emission spectra of (a) MgAl LDH, (b) g-C3N4, (c) ZnO and (d) g-C3N4\ZnO\Mg-Al LDH ternary nanocomposite, which were recorded using 320 nm as excitation wavelength. The LDH and ZnO nanoparticles exhibit a strong PL emission in the range from 350 to 450 nm. The pure g-C3N4 shows a strong emission about 420 nm, which can be attributed to the fast electron-hole

recombination process. It can be seen that, after the formation of ternary nanocomposite the emission was intensity was decreased which may due to the delocalization of electrons. In general, a decrease in the recombination rate gives rise to a low PL intensity, which results in the maximum photocatalytic activity.

latter part).

**113**

**Figure 7.**

*3.4.2 PL spectra*

which provides low photocatalytic activity.

#### **3.4 Photophysical investigation**

#### *3.4.1 UV-Vis absorption spectra*

Optical properties possess a prominent role in the photocatalytic materials and therefore the photophysical properties of the prepared materials were investigated by UV-Vis and PL analyses. The optical absorption analysis was done using a SHIMADZU 3600 UV-Vis-NIR spectrophotometer and Emission spectrum of the as-prepared samples was recorded by using Horiba Jobin Yvon Spectro Fluromax 4. **Figure 7A** shows the UV-Vis. absorption spectra of the prepared samples. The absorption maxima were observed in the range between 320 and 450 nm. And the absorption of ternary nanocomposite was extended to the visible region and show an obvious red shift compared with the other samples, which may because of the interaction between the ZnO, LDH, and g-C3N4. The 2D\2D formation demonstrates a reality that the as-prepared ternary nanocomposite noticeable light vitality which can thusly create more charge transporters offered to contribution in the photocatalytic efficiency. Tauc's plot was used to determine the energy bandgap of the samples and the obtained values are 2.6, 3.5, 2.57 and 2.81 eV for LDH, ZnO,

*LDH Ternary Nanocomposites: g-C3N4 Intercalated ZnO\Mg-Al for Superior… DOI: http://dx.doi.org/10.5772/intechopen.89325*

#### **Figure 7.**

peak were observed at 76.8 and 120.8 eV. The occurrence of Zn is seen from the two Zn 2p states as Zn 2P3\2 and Zn 2P1\2 corresponding to 1020.8 and 1043.8 eV respectively. It additionally uncovers that the Zn is available just in 2+ oxidation state which affirms the conceivable bonding between Zn and O [10]. The oxygen O 1s is deconvoluted into three peaks corresponding to the O<sup>2</sup> at 532.2 eV, OH species at 533 eV and CdOdO at 536 eV, respectively [46]. In over-all, the inferior binding vitality of O 1s peaks emerges from the bond between O2 and Zn2+ metal ions. The C 1s spectra can be deconvoluted into dual contributions such as 284.4 and 289 eV, assigned to the occurrence of sp<sup>2</sup> hybridized carbon atoms and C]*N*dC bonding [47], respectively. The N 1s spectra can be tailored into three basic peaks with the binding energies of 402, 404.1 and 405 eV, which are attributable to the binding of CdN, CdNdC, and NdN respectively [20]. Henceforth, the above

*XPS spectra of C3N4\ZnO\Mg-Al LDH ternary nanocomposite: (A) survey spectra and (B) high resolution*

*XPS spectra of (a) Mg 1s (b) Al 2p (c) Zn 2p (d) O 1s (e) C 1s (f)N 1s [34].*

*Assorted Dimensional Reconfigurable Materials*

observations affirm the formation of g-C3N4\ZnO\Mg-Al LDH ternary

mapping analyses.

**112**

**Figure 6.**

**3.4 Photophysical investigation**

*3.4.1 UV-Vis absorption spectra*

nanocomposite and the XPS results are in good agreement with FTIR, EDX and

Optical properties possess a prominent role in the photocatalytic materials and therefore the photophysical properties of the prepared materials were investigated by UV-Vis and PL analyses. The optical absorption analysis was done using a SHIMADZU 3600 UV-Vis-NIR spectrophotometer and Emission spectrum of the as-prepared samples was recorded by using Horiba Jobin Yvon Spectro Fluromax 4. **Figure 7A** shows the UV-Vis. absorption spectra of the prepared samples. The absorption maxima were observed in the range between 320 and 450 nm. And the absorption of ternary nanocomposite was extended to the visible region and show an obvious red shift compared with the other samples, which may because of the interaction between the ZnO, LDH, and g-C3N4. The 2D\2D formation demonstrates a reality that the as-prepared ternary nanocomposite noticeable light vitality which can thusly create more charge transporters offered to contribution in the photocatalytic efficiency. Tauc's plot was used to determine the energy bandgap of the samples and the obtained values are 2.6, 3.5, 2.57 and 2.81 eV for LDH, ZnO,

*(A) UV-Vis absorption spectra (B) Tauc's plots and (C) PL spectra of the prepared samples ((a) Mg-Al LDH and (b) ZnO (c) g-C3N4 (d) g-C3N4\ZnO\Mg-Al LDH ternary nanocomposite) [34].*

g-C3N4, g-C3N4\ZnO\Mg-Al LDH ternary nanocomposite, respectively. The UV-Vis absorption results show the considerable enhancement in the visible light absorption and it is because of this reason, an enhancement in the photocatalytic performance of the as-prepared photocatalyst is observed (discussed in the latter part).

#### *3.4.2 PL spectra*

The emission spectrum is produced because of recombination of the charge carriers and it provides hints about the proficiency of charge carrier transformation, trapping, and separation of the photo generated electrons-holes pairs. The strong PL emission profile usually indicates the quick recombination of electron-hole pairs which provides low photocatalytic activity.

**Figure 7C** shows the PL emission spectra of (a) MgAl LDH, (b) g-C3N4, (c) ZnO and (d) g-C3N4\ZnO\Mg-Al LDH ternary nanocomposite, which were recorded using 320 nm as excitation wavelength. The LDH and ZnO nanoparticles exhibit a strong PL emission in the range from 350 to 450 nm. The pure g-C3N4 shows a strong emission about 420 nm, which can be attributed to the fast electron-hole recombination process. It can be seen that, after the formation of ternary nanocomposite the emission was intensity was decreased which may due to the delocalization of electrons. In general, a decrease in the recombination rate gives rise to a low PL intensity, which results in the maximum photocatalytic activity.

Degradation %ð Þ¼ ð Þn C0 � C C0 ∗ 100 (2)

, OH

C is the dye concentration at time t from the start of the photocatalytic reaction. For the reusability purpose, the as-prepared photocatalyst collected after the photocatalytic reaction by centrifuging, washed with DDW and then dried at 60°C.

To elucidate the reaction mechanism of the photocatalytic MB dye degradation, the radical trapping investigation was performed. In the scavenging activity, h<sup>+</sup>

The photocatalytic activities of the Mg-Al LDH, g-C3N4, and g-C3N4\ZnO\Mg-Al LDH ternary nanocomposite were assessed under UV-Vis light illumination. In this work, MB dye was utilized as an objective contamination so as to decide the photocatalytic action of the impetuses under obvious light illumination. The MB dye solutions were prepared and the photocatalytic reactions were performed by adding the as-prepared samples to the MB dye solutions. The pure MB dye fragment shows a strong visible light absorption around 664 nm. The MB dye with prepared photocatalyst is subjecting under the visible light irradiation, corresponding absorption peak intensity was decreased, and the decreasing MB dye intensity is attributed to the degradation of MB dye through the photocatalytic activity. When increases the irradiation time, absorption intensity of MB dye molecules was decreased (i.e.) once increase the irradiation/reaction time, the large number of dye molecules can be degraded. In this process, a photocatalyst is irradiated by light with energy equal to or higher than the bandgap energy of the photocatalyst. This results in the excitation of an electron (e�) from the valence band to the conduction

surface of the photocatalyst in order to take part in the redox reactions with the

adsorbed oxygen and water molecules lead to the formation of superoxide radical

Among all the as-prepared photocatalyst samples, g-C3N4\ZnO\Mg-Al LDH ternary nanocomposite sample exhibit better photocatalytic activity. This could be attributed to a large number of electrons and holes generated by the as-prepared photocatalyst system, caused by the favorable visible light absorption. On the other hand, ZnO, a wide bandgap material, provides intermediate states to delay the electron–hole recombination, which could also contribute to the high photocatalytic activity. The morphological arrangements of the nanocomposite and its resultant electronic structure, (i.e.) the even distribution of ZnO intercalated LDH over the surface of g-C3N4 [49], collectively contribute to the effective separation of the photogenerated charge carriers. The observed photocatalytic degradation efficiencies of the as-prepared photocatalysts are 32%, 30%, 49% and 96.5% for ZnO, LDH,

g-C3N4, and g-C3N4\ZnO\Mg-Al LDH ternary nanocomposite, respectively.

OH), respectively.

adsorbed species. The redox reactions of electrons (e�) and holes (h<sup>+</sup>

) in the valence band. Before the recombination takes place,

) should be transferred to the

) with

The trapping experiments were carried out with the accumulation of different scavengers into the catalytic reaction. The reaction samples were taken from the

photocatalytic reactor to record their UV-Vis absorption spectra.

*LDH Ternary Nanocomposites: g-C3N4 Intercalated ZnO\Mg-Al for Superior…*

� radicals are trapped by EDTA, 2-propanol and benzoquinone, respectively.

where,

and O2

C0 is the initial dye concentration and

*DOI: http://dx.doi.org/10.5772/intechopen.89325*

**4.3 Reaction mechanism of dye degradation**

the photogenerated electrons (e�) and holes (h+

�) and hydroxyl radical (<sup>∙</sup>

**4.2 Radical trapping experiment**

band, leaving a hole (h<sup>+</sup>

anion (<sup>∙</sup>

**115**

O2

**Figure 8.** *BET surface area analysis of g-C3N4\ZnO\Mg-Al LDH ternary nanocomposite [34].*

### **3.5 Surface area investigation**

The specific surface area of the photocatalyst was determined by Brunauer-Emmett-Teller (BET) analysis through N2 adsorption/desorption measurements at 25°C (**Figure 8**). The measured surface area of the ternary nanocomposite was �37 m<sup>2</sup> <sup>g</sup>�<sup>1</sup> . The high surface area support more active species and reactants to be absorbed on its surface, which might proficiently help the kinetics of photo catalytic reaction.
