| Summary: | 碩士 === 國立成功大學 === 環境工程學系 === 106 === With the high fossil fuel consumption and high carbon dioxide (CO2) emission to the atmosphere has caused energy crisis and global warming. The photocatalytic and photoelectrocatalytic reduction of CO2 to low-carbon fuels, such as methane, methanol, formaldehyde and formic acid, become one of promising solutions. Therefore, preparing of novel photocatalysts for reduction of CO2 by photocatalysis and photoelectrocatalysis were investigated in this study.
The Cu2O/TiO2 heterojunctions were prepared by a facile soft chemical method, which was used for photocatalytic reduction of CO2. The Cu2O/TiO2 heterojunctions cause a red-shift to visible light region and improve separation of photogenerated electron-hole pairs. After a 6-h UV-vis irradiation, 21-70 µmol methanol/g-catalyst can be generated by the Cu2O/TiO2 heterojunctions, suggesting that Cu2O in junction with TiO2 may enhance the photocatalytic efficiency.
Carbonization of Ag+ and Cu2+ with -cyclodextrin (CD) to yield the (Ag/Cu2O)@C core-shell nanoparticles were used for photocatalytic reduction of CO2. Moreover, the core metals were partially etched to form the (Ag/Cu2O)@C yolk-shell nanoreactors. The diameters of the core (Ag/Cu2O) in the (Ag/Cu2O)@C yolk-shell nanoreactors are 14-25 nm observed by TEM images. Under a 6-h light irradiation, 7-19 µmol/g-catalyst of methanol are yielded by the (Ag/Cu2O)@C core-shell nanoparticles, indicating Ag deposited on Cu2O acting as electron sinks leads to a better photocatalytic efficiency. More methanol up to 74.7 µmol/g-catalyst can be obtained by the (Ag/Cu2O)@C yolk-shell nanoreactors. It seems that the (Ag/Cu2O)@C yolk-shell nanoreactor provides more space within the carbon-shell, which facilitates the methanol formation, and thus a higher yield of methanol can be achieved.
To reduce the rapid recombination rate of the photogenerated electron-hole pairs, the Cu2O/TiO2 heterojunction photoelectrode were prepared for photoelectrocatalytic reduction of CO2. The Cu2O/TiO2 heterojunctions have a low bandgap energy and present a high photocurrent density in the linear sweep voltammetry. By EIS and Mott-Schottky plots, the Cu2O/TiO2 heterojunctions show a less electron transfer resistance and a decrease in band bending as the heterostructure may promote the interfacial charge transport. After UV-vis illumination for 6 h, 11.13 μmol/cm2 of methanol are yielded and the faradaic efficiency can reach 88% by the Cu2O/TiO2 heterojunction films.
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