Synthesis of solar and visible-light-active highly ordered titania nanotube arrays (TNTS) for photocatalytic applications / Sim Lan Ching

Sim, Lan Ching (2015) Synthesis of solar and visible-light-active highly ordered titania nanotube arrays (TNTS) for photocatalytic applications / Sim Lan Ching. PhD thesis, University of Malaya.

Preview

PDF (Thesis PhD) Download (5Mb) | Preview

Abstract

The present contribution work focused on the development of solar-light and visible light responsive binary and ternary TiO2 nanotube arrays (TNTs) based composite photocatalysts. The developed photocatalysts were implemented for the competent removal of dye and phenolic derivative from the liquid waste. The implication was also extended for the photocatalytic conversion of CO2 and H2O to light hydrocarbon. The binary composite was achieved by mashing-up the semiconductor oxides namely nickel oxide (NiO) and tin oxide (SnO2) with TNTs through impregnation route. The morphological analysis revealed that both of the binary composite are bunches free, self organized and highly ordered with better geometry. The inclusion of semiconductor oxides onto TNTs significantly promoted the shift towards the visible light spectrum than that of the unmodified TNTs. The same was reflected in the solar-light-driven photocatalytic degradation of prominent cationic dye solution, methylene blue (MB) which was adopted as model pollutant for the binary composite with varied loading. However, the increasing loading of both NiO and SnO2 did not exert significant effect on the degradation efficiency of MB. The visible light development was approached further by including the noble metals and conducting carbon materials. This led to the formation of ternary composite, bound the localized surface plasmon resonance (LSPR) and efficient electron transport endorsed by Ag and GO, respectively. The light source was truncated to artificial visible light to eliminate the unsteady illumination conditions as seen in solar spectrum. Implicit microscopic and spectroscopic techniques substantiated the significance of the presence of Ag as nanoparticles (NPs) and the role of GO in the ternary composite. The ternary exhibited a more appreciable red shift towards the visible range and plunged the recombination of the electron-hole pair compared to that of the binary. The photocatalytic investigation was carried out by degrading MB and additionally chlorinated compound, 2-chlorophenol (2-CP)comprehensively along with their uniqueness in the degradation mechanism. The reusability studies showed a deprived performance for MB degradation than that of 2- CP, due to the chemisorption of MB. The successful results from our continuous work motivated us to further explore the possibility of combining graphene (RGO) and platinum (Pt) for a complicated gas phase conversion of carbon dioxide (CO2) to light hydrocarbon under visible light irradiation. This ternary composite was synthesized by depositing rapid thermally reduced GO over the surface of TNTs which was predeposited with Pt. The resulting composite demonstrated a stunning visible light absorption over the others. The prepared composite exhibited its accomplishment by energetically photoreacting CO2 with H2O for the production of methane. This synergetic CH4 production rate was attributed predominantly to the coexistence of RGO and Pt which efficiently prolonged the lifetime of the photoinduced electrons and extended the visible light response. Thus the present thesis enlightened and overcame with much promising composite photocatalysts that upbeat the limitations experienced by most of the conventional photocatalysts. It also provided a demanding sustainable and greener solution for environmental cleanup and greenhouse gas reduction through alternative fuel generation.

Actions (For repository staff only : Login required)