الفهرس 
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Abstract
In first part, a composite of tubular g-C3N4 with α-Fe2O3 has been synthesized to improve the photocatalytic performance of tubular g-C3N4 by the formation of a Z-scheme heterostructure. The composites were fabricated by the combination of varying amounts of hydrothermally synthesized α-Fe2O3 nanotubes (NTs) and protonated ruptured tubular (RT) g-C3N4, by the electrostatic self-assembly method. The obtained composites were characterized by zeta potential, p-XRD, scanning/transmission electron microscopy (S/TEM), PL, and FTIR. PL and photocurrent measurements indicates a higher charge separation of the photo-generated electron-hole pair for Fe2O3 NTs/RT g-C3N4 composite with higher concentration of α-Fe2O3 NTs. UV-Vis diffuse reflectance spectroscopy (UV-Vis/DRS) shows the band gaps of pristine α-Fe2O3 NTs and RT g-C3N4 to be 1.86 eV and 2.72 eV respectively, while the band structures were determined by Mott-Schottky measurements. I-V curves obtained from photoelectrochemical water splitting shows that the formation of the composite decreased the oxidation overpotential as compared to pristine α-Fe2O3 NTs and pristine RT g-C3N4. Bode plots showed that the composite was able to increase the lifetime of the photo-generated electrons as compared to both RT g-C3N4 and α-Fe2O3 NTs.
In second part, ruptured tubular structured of graphitic-carbon nitride (RT g-C3N4) was successfully prepared, followed by in-situ growth of carbonate-intercalated ZnCr layered double hydroxide (ZnCr-CO3 LDH) on its surface by the co-precipitation method. The fabricated composites contain varying amounts of the LDH. An increase in the specific surface area of the g-C3N4/LDH composite (103.74 m2/g) was observed as compared to RT g-C3N4 (7.55 m2/g) and pristine LDH (11.26 m2/g), by the nitrogen adsorption-desorption isotherm (BET) technique. The formation, morphology and the chemical composition of the pristine RT g-C3N4, pristine LDH and composites were examined by p-XRD, SEM, EDS, TEM, and FTIR. Optical measurements by UV-Vis/DRS revealed that the band gap of the composites can be tuned by varying the LDH concentration in the composite. The ability towards the separation of photo-generated electron-hole pairs was examined by PL and the curves of transient photo-current with time, which inferred that the composite with higher content of LDH (RT g-C3N4/ LDH3) had the highest activity amongst the prepared materials. Mott-Schottky measurements were carried out to determine the flat band potential. Finally, the photoelectrocatalytic activity represented by measurements of transient photo-current with time (I-t curve), electrochemical impedance spectroscopy, and linear sweep voltammetry (I-V curve) was examined. It inferred that the formed composite (RT g-C3N4/ LDH3) had enhanced the photoelectrochemical water oxidation by around 2.4 and 1.4 fold with respect to pristine RT g-C3N4 and ZnCr
LDH, respectively.