1. UKM Learning and Research Repository
2. PHD Thesis / Tesis PHD
3. Faculty of Engineering and Built Environment / Fakulti Kejuruteraan dan Alam Bina

Title:	Photocatalytic degradation of organic pollutants and reduction of carbon dioxide over silver-based phocatalysts
Authors:	Samsun Nahar (P83340)
Supervisor:	Muhammad Fauzi Mohd Zain, Prof. Dr.
Keywords:	Universiti Kebangsaan Malaysia -- Dissertations Dissertations, Academic -- Malaysia Photocatalytic degradation Organic pollutants Phocatalysts
Issue Date:	1-Aug-2020
Description:	In recent times, the photocatalytic organic pollutant degradation and CO2 reduction reactions over silver-based photocatalysts have attracted much consideration due to their great prospects. The major drawbacks on the path of achieving high performance in these photocatalytic reactions are; photocatalysts with low visible light activity, capable of only degrading dye compounds, degrading pollutants into more toxic compounds and low rate of product selectivity in CO2 reduction with H2O. Hence, this research aimed to characterize visible light active, fabricated Ag-based plasmonic, and hybrid photocatalysts. The photocatalytic activities of the synthesized catalysts were determined for model organic pollutant rhodamine B (RhB) and phenol degradation, also for CO2 reduction with H2O. The effect of catalysts' structure, different reaction parameters, nature of the dye compounds on these photocatalytic processes and their reaction fundamentals were investigated. The reduced Ag2SO3 (AgSS) with surface Ag nanoparticles (NPs) were prepared by precipitation and chemical reduction method then labeled as 1-AgSS, 5-AgSS, 10-AgSS based on their anticipated molar ratios of Ag0 to Ag+ and the hybrid AgCl/Ag2SO4 (SCS), AgCl/Ag2SO4/Ag2SO3 (SCSS) catalysts were synthesized by an in-situ precipitation method then characterized using selective instrumental measurements. In Rh B and phenol photo-degradation reactions, changes in the pollutant solution color were observed by UV-spectra, phenol degradation percentages were determined by High Performance Liquid Chromatography analysis, and its reaction intermediates were identified using Gas chromatography-mass spectrometry. These prepared photocatalysts were further studied for CO2 reduction with H2O in solid-phase reactions. The impact of the acid-base additives in CO2 reduction was investigated over the optimum catalyst composition, in liquid phase experiments. The CO2 conversion and yield of the product were analyzed using Gas Chromatography-Thermal Conductivity Detector. The source of carbon in the obtained products was verified by a series of blank tests and Fourier-transform infrared spectroscopy analysis of the freshly prepared catalysts. Over 1-AgSS catalyst, 99% degradation of RhB was observed under artificial visible light and natural sunlight due to the Surface Plasmon Resonance (SPR) effect of small, cubic Ag NPs. This catalyst showed improved performance at high and low pH environment and exhibited the capability of degrading other dyes apart from RhB as well as reusability. The results of phenol degradation experiments revealed an opposite order of photo-activity for AgSS composites, where 10-AgSS was the most effective. The SCS, and SCSS catalysts successfully removed 86% and 93% of phenol, respectively attributed to their integrated hybrid structures. Here the SCSS with three different reaction sites and shorter bandgap showed better efficiency than SCS. These synthesized Ag-based catalysts also showed high selectivity towards CO2 conversion with H2O into CO. Over 5-AgSS, the highest yield of CO (18.2 μmol/g) was achieved in solid-phase CO2 reduction, and in the liquidphase reaction, an increased amount of CO (22.8 μmole/g) was produced with a trace amount of HCOOH. In aqueous, H2SO4 the CO production rate reaches the highest value due to the surface negativity of 5-AgSS, which led to the reduction of CO2 with additional electrostatically influenced pathways. All these results verify the high possibility of using fabricated Ag-based photocatalysts for complete degradation of organic pollutants and selective reduction of CO2 under visible light exposure.,Ph.D.
Pages:	169
Publisher:	UKM, Bangi
Appears in Collections:	Faculty of Engineering and Built Environment / Fakulti Kejuruteraan dan Alam Bina

Items in DSpace are protected by copyright, with all rights reserved, unless otherwise indicated.