| Photodegradation of organic pollutants using semiconductors is a cost efficient way to remove dyes from industrial water. However, the use of bare semiconductors, such as TiO2 or ZnO, is limited due to their wide band gap and high recombination rate of photogenerated charges. Couplingwith noble metal or grapheneis emerging as an efficient way for theimprovement of degradation rate of organic pollutants. Meanwhile, much attention has been paid to the photoelectrocatalytic approaches to degrade organic pollutants.In this work, focusing on the enhanced photocatalytic performance of metal oxide photocatalysts, ZnO nanorod/Au composite nanoarrays, CuO nanowires/Ag composite nanoarrays, Cu2O/Cu composites, graphene-wrapped octahedral Cu2O nanocomposites, and graphene/CuO nanosheet composites have been fabricated to investigate the effect of noble metal and graphene on photocatalytic property. In addition, perovskite solar cell has been combined with graphene/CuO nanosheet catalytic electrode to understand photoelectrocatalytic property.In this dissertation, main contents are summarized as follows:1. The photocatalytic performance of metal oxide was increased by decoration of noble metal. First, a high-performance photocatalyst of ZnO nanorod/Au composite arrays was synthesized using Sn2+ as ’bridge’ and reducer. The unique nanostructured composite showed great adsorptivity of dyes, enhanced light absorption intensity, and extended light absorption range simultaneously due to the introduction of Au. Hence, a significant enhancement in the photocatalytic properties in comparison with pure ZnO as demonstrated in photodegradation of methyl orange due to the incorporation of Au nanoparticles in ZnO nanorods. Then, CuO nanowires were grown on Cu foil via a simple cost-effective wet-chemical route in large scales and used as templates for making silver-coated CuO composite nanowires. The coverage of Ag on CuO nanowires was controlled by varying the concentration of Ag precursor. And the light absorption ability for composites with different Ag content was also tested. The composites were evaluated for their ability to degrade methyl orange solution under solar light irradiation, In addition, the effect of Ag loading to the photocatalytic efficiency was also discussed. The rate of degradation of the as-prepared composites was more than 7 times faster than that of using pure CuO nanowires under solar light irradiation when the concentration of AgN03 was 4 mM. It was found that the composite arrays not only exhibited high photocatalytic activity and stability, but were also easy to recycle due to the direct growth on the substrate, which make it possible for the use of this kind of photocatalysts in practical environment treatment. Cu2O/Cu composite particles can be synthesised by one-step sono-chemical process using CUSO4 as precursors and N2H4H2O as reducers. The content of Cu in the Cu2O/Cu composites can be easily controlled by adjusting the synthesis time. Results demonstrated clearly that Cu2O/Gu were stable and resistant to photocorrosion during the photocatalytic oxidation of organic compounds.2. The photocatalytic performance of metal oxide was increased by introduction of graphene. (GO) was prepared by modified Hummers’ method first. Reduced graphene oxide (rGO)-wrapped octahedral Cu2O composites were successfully produced by an ultrasonication-assisted reduction of GO in the Cu2O precursor solution. During the ultrasound reaction, the reduction of GO and the growth of octahedral Gu2O crystals occurred simultaneously in conjunction with the deposition of Cu2O crystals on graphene. As a result of the introduction of rGO, the light absorption of octahedral Cu2O was markedly improved, the size of Cu2O crystals was decreased, and the self-aggregation of Gu2O crystals was effectively prevented. More importantly, the charge separation and transfer were effectively enhanced due to the introduction of rGO. Compared to the pure octahedral Cu2O crystals, the composites exhibited an increased degradation rate of MO by 4.5 times. Then, Graphene/CuO nanosheet composite arrays were prepared by a simple, efficient, yet versatile method using GO as precursor. The growth machanism of CuO nanosheet was discussed by controlling the synthesis time of CuO. As the result of SEM, the deposition of RGO had no significant influence on the morphology of CuO nanosheet. The obtained composite nanoarrays with different rGO content were applied as photocatalyst for the degradation of MO, which showed enhanced photocatalytic performance. When the concentration of GO was 0.5 mg/mL, the degradation rate of the as-prepared composites was the highest, which was 1.5 times faster than that of pure CuO nanosheet. After the combination of perovskite solar cell with graphene-CuO composite catalytic electrode, the photocatalytic efficiency was further increased, which indicated the outstanding photocatalytic property of photoelectrocatalyst. This is the first time to get graphene wrapped-Cu2O and cover graphene on the surface of CuO nanosheet, which find a new way for the combination of graphene and metal oxide. Also, this is the first time to introduce the perovskite solar cells into photocatalytic system to increase the photoctalytic efficiency, which provide a new idea for the enhanced photocatalytic research and the application of perovskite solar cells.3. The enhanced photocatalytic activity mechanisms of the introduction of noble metal, graphene and perovskite solar cells have been discussed on the base of photoluminescence spectra, photocurrent spectra and electrochemical impedance spectra. And the mobility mechanism of photo-generated electrons in composite materials was proposed. The photocatalytic property of metal oxide was increased by noble metal due to the enhanced visible-light absorption and the separation of photo-generated electrons and holes. The photocatalytic property of metal oxide was increased by graphene due to the enhanced adsorption of organic dyes, visible-light absorption and the separation of photo-generated electrons and holes. The introduction of perovskite solar cells was used to induce the separation of photo-generated electrons and holes. It was found that the efficient separation of photo-generated electrons and holes was the key factor to the enhanced photocatalytic property by the comparison of three different enhanced methods, which was helpful for the further research about enhanced photocatalysis. |
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