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Title:	Photocatalytic reduction of CO2 to methanol under visible light irradiation using N-CEO2-TIO2 catalyst
Authors:	Hamidah Abdullah (P65745)
Supervisor:	Zahira Yaakob, Prof. Ir. Dr.
Keywords:	Global warming Photocatalysis
Issue Date:	2-Dec-2018
Description:	Carbon dioxide (CO2) is one of the greenhouse gases that contributes to global warming. CO2 could be converted to valuable products such as hydrocarbons through photocatalytic process. The photocatalytic reduction of CO2 using titanium dioxide (TiO2) as a catalyst has attracted the interest of researchers in past few years. However, the TiO2 catalyst still has a limitation in terms of application under visible light. Besides, it also has low charge carrier and CO2 adsorption which affects the product yield. Therefore, it is important to develop a novel photocatalyst with improved properties for photocatalytic reduction of CO2 to hydrocarbon under visible light irradiation. The synthesized TiO2 was used as the basis for the design of novel catalyst. In this work, a series of TiO2 modified by adding cerium (CeO2-TiO2) were synthesized using the impregnation method by varying the cerium loading (1 to 5 wt %) and calcination temperatures (400 to 800 °C). Then, the N-CeO2-TiO2 catalyst was synthesized using different nitrogen sources (hydrazine and triethylamine). The physicochemicals and optical properties of the as-prepared catalysts were investigated through XRD, nitrogen adsorption-desorption, FESEM, TEM, FTIR, UV-VIS NIR Spectrophotometer, PL Spectrophotometer, XPS and CO2 adsorption analysis. The performance of the photocatalyst was evaluated in terms of methanol (CH3OH) yield. The 2 wt % of cerium loading (CeO2-TiO2) and calcined at 500 °C was found to have a lower band gap, higher surface area and lower rate of electron-hole recombination rate as compared to TiO2. Those properties contribute in enhancing production yield of CH3OH whereas the highest yield was 18.6 μmol/g.catalyst. It is worthy to say that the CH3OH yield could increase up to 39.6 μmol/g.catalyst by modifying the CeO2-TiO2 with triethylamine (N-CeO2-TiO2). A further study was performed by investigating the effect of different reaction time (1 - 10 hours), catalyst loading (0.5 g/L - 2.0 g/L) and light intensity (65 W/m2 - 305 W/m2) on CH3OH yield using one factor at one time (OFAT). Optimum reaction conditions were obtained from Design of Experiment (DOE) study whereby it was found that 7 hour irradiation time, 1.1 g/L catalyst loading and 500 W of light power should be used to result in 39.48 μmol/g.catalyst of CH3OH using N-CeO2-TiO2 (triethylamine) catalyst. The highest yield using this catalyst is due to the existence of mixture Ce3+/Ce4+ and nitrogen element which could inhibit the electron/hole recombination and could adsorb visible light and more CO2. The proposed reaction mechanisms are classified from experimental and theoritical calculation studies while the kinetic model was proposed based on Langmuir-Hinshelwood and it fitted well with the experimental data. Moreover, the modified catalyst exhibited recycle ability up to four cycles where the loss of activity was ~40%. It can be concluded that the novel catalyst for the photocatalytic reaction that is active under visible light irradiation was successfully synthesized with highly effective reduction of CO2 to CH3OH.,Ph.D.
Pages:	170
Call Number:	QD181.C1H336 2018 3 tesis
Publisher:	UKM, Bangi
Appears in Collections:	Faculty of Engineering and Built Environment / Fakulti Kejuruteraan dan Alam Bina

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