| Summary: | 碩士 === 國立臺灣大學 === 化學工程學研究所 === 89 === The main purpose of this study is to reduce the amount of carbon dioxide by artificial photosynthesis, and derive a reasonable calculation of photoefficiency.
The photocatalytic reduction of carbon dioxide with H2O in aqueous phase was carried out with the catalysts suspended in 300ml of purified water and 0.2M NaOH solution in a water bath at 295K, ambient pressure. After the solution is saturated by bubbling CO2 (99.9999﹪V) for 30min, it was irradiated with a UV lamp (λ=254nm).The major reduction products collected in the liquid phase analyzed by gas chromatography were methanol, in addition, we detect small amount of oxygen.
The procedure of catalyst preparation is that we take the solution containing CuCl2 added to a solution which contained Ti(OC4H9)、n-C4H9OH and CH3COOH, resulting in a sol consisting of Cu2+-loaded TiO2, the Cu/TiO2 weight ration depends on the amount of CuCl2
In order to get the best condition of photocatalytic reduction of carbon dioxide, we used the 1.98 wt﹪Cu/ TiO2 as the photocatalyst, and tried to change the environment of experiments, such as pH value, reaction time, the amount of catalysts and the carbon dioxide pressure etc… It was found that we can get the best catalytic reactivity when the concentration of catalyst is 0.1g/L, the concentration of NaOH is 0.2M and the pressure of CO2 is 125.8 kPa.
From the experiments we find out that the yield of methanol with Cu/TiO2 is much higher than with bulk TiO2. It proves that the loading of Cu really enhance the catalytic reactivity. A 550 (μmole/g) yield of methanol gives the most active powders ,with the Cu loading amount of 1.98 wt﹪ on irradiation with UV light for 36th hours. In addition, we got the highest photoenergy efficiency： 2.5%； Quantum efficiency ：10.02% in this system。
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