| Summary: | 碩士 === 國立臺灣大學 === 化學工程學研究所 === 101 === Global warming becomes a serious problem due to the industrial revolution and the progress of the human civilization. The petroleum is also limited source on earth. The reason that the temperature increases on the earth is because of the greenhouse gases. One of the main greenhouse gases is CO2 from the combustion of fossil fuel. One of the best routes to solve the problem is the photo process that utilizes solar energy to drive the water splitting reaction. A Z-scheme of water splitting has the potential to use solar energy to split water into hydrogen and oxygen. The Z-scheme system contains two types of photocatalysts, one is H2-photocatalyst, and the other is O2-photocatalyst. By irradiation of the visible light, electrons and holes are generated on both photocatalyst. With the help of redox mediator, we could utilize visible light to split water into hydrogen and oxygen.
In this research, we developed the visible-light driven photocatalysts. SrTiO3:Rh was prepared by sol-gel method. This H2-photocatalyst was to produce H2 in the overall water splitting. The O2-photocatalyst, WO3, was received from a commercial manufacturer for the oxidation of water to form O2. The H2-photocatalyst and the O2-photocatalyst were loaded with Pt by incipient wetness method. The former is reduced under H2 and the later is calcined in air, respectively. The twin reactor is divided by Neosepta anion exchange membrane. We applied the H2-photocatalyst and O2-photocatalyst to run the overall water splitting in the presence of I-/IO3- redox mediators. The light source was 300W Xenon lamp. The optimized concentration of the redox mediator I-/IO3- was under 15 mM NaI solution initially for both side of the twin reactor, which was found to give the highest amount of hydrogen evolved. The results showed that 10 μmol/g‧cat H2 was evolved under the ratio of O2/H2 equal to 0.49 at the end of 6 hours. The amount of 13 μmol/g‧cat H2 was evolved under the ratio of O2/H2 equal to 0.63 at the end of 8 hours. The backward reaction of water splitting can be avoided by using the twin reactor. In addition, the cost of H2/O2 separation can be saved, and also the potential explosion of H2/O2 mixture can be prevented. In the twin reactor, H2-photocatalyst and O2-photocatalyst were separated so that light energy can be fully utilized.
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