| Summary: | 碩士 === 國立宜蘭大學 === 環境工程學系碩士班 === 104 === Hydrogen is considered as a promising energy source with its high energy yield, renewable, environment friendly properties. TiO2 modified with noble metal and nonmetal is widely used. In this study, Pt and graphene (GN) were used to modify TiO2 nanoparticles. GN/TiO2, Pt-TiO2, Pt-GN/TiO2 were successfully synthesized by modified Hummers’ method, alcohol thermal and photodeposition method, respectively. The characterizations of the synthesized catalysts by UV-vis/DRS, components analysis, XRD, FTIR, SEM-EDS and TEM analysis were conducted.
The maximum hydrogen production rate was approximately 4.71 mmol h-1 g-1 when the Pt content was 1.0 wt.%. Higher and lower than 1.0 wt.% of Pt loading content both result in low efficiency of hydrogen production. The highest hydrogen production rate is 6.58 mmol h-1 g-1 by 1.5 wt.% Pt-5 wt.% GN/TiO2 (1.5PTG5), which is about 1.4 and 2.2 times higher than that of Pt-TiO2 and GN/TiO2 binary composites, respectively. The rate of 6.03 mmol h-1 g-1 was achieved by 0.5PTG10 with only 0.5 wt.% Pt , and only a little lower of hydrogen production efficiency than that of 1.5PTG5. Therefore, the utilization of low-cost graphene can reduce the use of noble metal Pt in photocatalytic hydrogen production. The mechanism of Pt-GN/TiO2 for the improved photocatalytic activity is proposed. 0.1 g L-1 is found to be the optimum catalyst concentration for optimal hydrogen production. Excess catalyst may result in opacity of the reaction solution and the light intensity is decreased. In addition, different sacrificial agents (methanol, ethanol, n-propanol, i-propanol, n-butanol, ethylene glycol, 1,2-propanediol, 1,3-propanediol and glycerol) have been investigated. There is clearly a linear relationship between hydrogen production rate and the polarity of monohydric alcohols. At higher initial methanol concentration, the hydrogen production rate should become constant, which make the reaction match with zero-order kinetics. At lower initial concentration, the hydrogen production rate was proportional to the initial methanol concentration. In addition, the photocatalytic hydrogen production reaction process satisfied the pseudo-first order equation with an rate constant kK at lower initial concentration. According to the Langmuir-Hinshelwood results, the surface pseudo-first order rate constant k = 15.06 mmol h-1 g-1 and the adsorption coefficient K = 0.50 mol L-1 were obtained. After reusing the catalyst under the same experimental conditions, the hydrogen production rate has only slightly decreased for 3 more cycles, which indicated the stability of the synthesized catalysts.The feasibility of hydrogen production from wastewater obtained from terephthalic acid industry was studied.
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