Research Papers - School of Natural Sciences
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Publication Open Access Efficient photocatalysis of Cu doped TiO2/g-C3N4 for the photodegradation of methylene blue(Elsevier, 2023-03-06) Liyanaarachchi, H; Thambiliyagodage, C; Liyanaarachchi, C; Samarakoon, UThe release of dyes into normal water reservoirs has become a tremendous environmental problem and the development of methods to remove such dyes is essential. A novel photocatalyst was fabricated in which Cu doped to TiO2 was coupled with g-C3N4 (Cu-TiO2/g-C3N4) in different weight percentages as 10, 30 and 50%, hydrothermally. Pure TiO2 consisted of both Anatase and Rutile phases where slight lattice distortions were observed in the Cu-doped TiO2 as evidenced by the XRD and Raman analysis. Cu was present at 1.7% by weight respective to TiO2 according to the XRF analysis. Spherical and irregularly shaped aggregated Cu-doped TiO2 nanoparticles in the range of 15–55 nm were heterogeneously distributed on the g-C3N4 matrix as observed by TEM and SEM. The band gap of TiO2 (3.0 eV) was reduced to 2.67 upon doping with Cu. The band gap of g-C3N4 was found to be 2.81 eV and that of Cu-TiO2/g-C3N4 in different weight percentages were in the range of 2.82 to 2.88 eV. Synthesized photocatalysts were tested on the ability to degrade methylene blue under UV and Visible light. Cu-TiO2/50% g-C3N4 showed the highest rate constant (4.4 × 10-3 min−1) which is 5 and 9.8 times greater than TiO2 and g-C3N4, respectively. The rate constant decreased with the introduction of EDTA and Isopropyl alcohol as they scavenge holes and hydroxyl radicals, respectively. The photocatalytic activity of all the nanomaterials increased with the increasing concentration of persulfate due to the increasing concentration of SO4●- and OH● produced. Synthesized nanomaterials effectively adsorb methylene blue under dark conditions following the pseudo-second-order kinetics suggesting that methylene blue molecules were chemisorbed to the adsorbents. The adsorption rate constant resulting in the best-performing photocatalyst was 0.122 g mg−1 min−1. Hence, it is evident that Cu-TiO2/g-C3N4 can effectively degrade methylene blue.Publication Open Access Fabrication of dual Z-scheme g-C3N4/Fe2TiO5/Fe2O3 ternary nanocomposite using natural ilmenite for efficient photocatalysis and photosterilization under visible light(Elsevier, 2022-11-11) Thambiliyagodage, C; Liyanaarachchi, H; Kumar, A; Jayanetti, M; Usgodaarachchi, L; Lansakara, BThe advanced oxidation process is a prominent method available to remove dyes released to normal water reservoirs to alleviate water scarcity. We report the fabrication of novel g-C3N4/Fe2TiO5/Fe2O3 using natural ilmenite sand as the precursor of the metallic semi-conductors exploration of a heterostructure for photodegradation of methylene blue under sunlight. Ternary composites were synthesized by varying g-C3N4 with respect to Fe2TiO5/Fe2O3 and varying Fe2TiO5/Fe2O3 with respect to g-C3N4 where the varying component was varied as 8, 24 and 40%, respect to the constant material. The hybridization of the three semi-conductors has been confirmed by the microscopic, chemical, and structural analyses. X-ray diffraction patterns show the presence of all three g-C3N4, Fe2TiO5 and α-Fe2O3 while the transmission electronic microscopic and scanning electronic microscopic images show the heterogeneous distribution of the metal oxide nanoparticles on g-C3N4 matrix forming the composite. HRTEM images further reveal the junction of Fe2TiO5 and α-Fe2O3. X-ray photoelectron spectra show the existence of s-triazine and heptazine rings in the composites with Fe3+ and Ti4+ as the only oxidation states of Fe and Ti. Fe2TiO5/Fe2O3/40% g-C3N4 with bandgap of 2.63 eV calculated by diffuse reflectance UV-Visible spectroscopy showed the highest photocatalytic activity (0.009 min−1) being 1.3 times greater than the Fe2TiO5/Fe2O3 nanoparticles. Enhanced photocatalytic activity over the fabricated composites was observed due to the increased visible light absorption, efficient charge separation and improved charge transportation. g-C3N4 coupled with 40% Fe2TiO5/Fe2O3 showed the highest antibacterial activity against gram-negative E.Coli. The synthesis of dual Z-scheme g-C3N4/Fe2TiO5/Fe2O3 ternary composite provides new sights in developing novel photocatalysts using natural ilmenite sand for environmental applications.Publication Embargo One pot synthesis of α-Fe2O3/turbostratic carbon composites and their photocatalytic activity under sunlight(Elsevier, 2021-10-01) Thambiliyagodage, C. J; Nakandala, S; Siriwardana, B; Lansakara, BSucrose naturally obtained from sugar cane was catalytically graphitized by incorporation of varying amounts of iron (1, 5, 7.5 and 10%) as a one-pot synthesis. The weight of iron was varied relative to the weight of sucrose. Synthesized sucrose-Fe2O3 nanocomposites (FeGC) were characterized by X-ray diffractometry (XRD), Raman spectroscopy, and UV-Visible spectroscopy. It is observed that turbostratic carbon is produced upon the incorporation of iron and the percentage of graphitization increase with increasing loading of iron as revealed by XRD analysis. Quantitative analysis of Raman spectra confirm that the ordering of carbon increase with increasing loading of iron. The equilibrium adsorption capacity of carbon with the highest iron loading (10FeGC), 0.50 mg/g is higher than that with carbon without any metal, AC (0.2 mg/g), and the highest adsorption capacity (0.58 mg/g) resulted in carbon with 5% iron (5FeGC). Methylene blue adsorption to AC and carbon with 1% iron (1FeGC) followed pseudo-first-order kinetics and carbon materials with 5, 7.5 and 10% iron followed pseudo-second-order kinetics. The initial rate constant for the photodegradation of methylene blue in the presence of AC was 0.001 min−1 and that of 1FeGC (0.005 min−1) increased with increasing loading of iron where the highest initial rate constant (0.158 min−1) was obtained with 10FeGC. Ordered carbon enhances photocatalytic activity by being photoactive and increasing the separation of charges generated at α-Fe2O3.Publication Embargo Photocatalytic activity of N, Fe and Cu co-doped TiO2 nanoparticles under sunlight(Elsevier, 2021-01-01) Thambiliyagodage, C. J; Usgodaarachchi, LPhotocatalytic activity of N doped with one transition metal is well known. This article reports the synthesis of TiO2 nanoparticles doped with only N, N co-doped with Fe, N co-doped with Cu and N co-doped with both Fe and Cu by sol-gel method. Their photocatalytic activity was evaluated for the degradation of methylene blue under sunlight. Nanoparticles were characterized by X-ray diffractometry (XRD), Raman spectroscopy, transmission electron microscopy (TEM), scanning electron microscopy (SEM), and diffuse reflectance UV–visible spectroscopy (DRS). XRD analysis revealed the presence of anatase phase TiO2 nanoparticles which was confirmed by Raman spectroscopic and TEM analysis. The crystal structure has not been disturbed by doping with N, Fe and Cu as shown by both XRD and Raman analysis. TEM and SEM images exhibit the nanoparticles which are interconnected due to sintering. XPS analysis revealed the presence of the only Ti4+ in undoped TiO2 but both Ti4+ and Ti3+ are present in doped TiO2 nanoparticles. According to the DRS analysis, the band gap of all doped TiO2 is lower than that of the undoped TiO2, where N, Fe and Cu co-doped TiO2 showed the lowest band gap (2.51 eV) proving that the visible light sensitivity of TiO2 increase with metal and non-metal doping. The rate of photodegradation of methylene blue in the presence of undoped TiO2 (0.016 min−1) is higher than all the doped TiO2 nanoparticles. N doped TiO2 show the highest activity among the doped TiO2 nanoparticles (0.006 min−1). Doped TiO2 nanoparticles showed a lower photocatalytic activity due to the electron hole pair recombination and the shielding effect of the dopants.