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This dissertation, Metal Sulfide and Graphene Co-modified Photocatalysts With Enhanced Visible Light Responses for Photocatalytic Organic Degradation and Hydrogen Generation by Jianfei, Peng, 彭劍飛, was obtained from The University of Hong Kong (Pokfulam, Hong Kong) and is being sold pursuant to Creative Commons: Attribution 3.0 Hong Kong License. The content of this dissertation has not been altered in any way. We have altered the formatting in order to facilitate the ease of printing and reading of the dissertation. All rights not granted by the above license are retained by the author. Abstract: Abstract of thesis entitled Metal sulfide and graphene co-modified photocatalysts with enhanced visible light responses for photocatalytic organic degradation and hydrogen generation Submitted by PENG Jianfei for the Degree of Master of Philosophy at The University of Hong Kong in November 2015 Energy crisis and wastewater pollution are two major problems that the human being must face in nowadays and future. Photocatalysis is a potential technology not only for efficient removal of organic pollutants in wastewater, but also for generation of hydrogen from water. Hydrogen is a green and reusable energy source with a high combustion value and zero greenhouse gas emissions. Both photocatalytic oxidation and reduction reactions may be performed in the presence of effective photocatalysts. However, most photocatalysts response only to UV light, and the activity of photocatalysts has been greatly suppressed by the quick recombination of photo-induced electron-hole pairs. To overcome these obstacles, loading cocatalysts is considered as an effective way of modification to improve the photocatalytic activity of the catalysts. In the studies reported in this thesis, layer-structured MoS /graphene (GR) hybrids were incorporated into the main catalyst of AgBr during its synthesis to form the AgBr-MoS /GR nanocomposites for enhanced photocatalytic organic degradation, and NiS nanoparticles and GR nanosheets were incorporated into CdS to form the CdS-NiS-GR composites for photocatalytic hydrogen generation. By the modification with the cocatalysts, the reactivity of the composite photocatalysts under visible light greatly improved. The structural and morphological properties of the composite catalysts were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDS) and N adsorption/desorption analysis. The organic removal activity of the AgBr-MoS /GR was tested by the degradation of rhodamine B dye as a model organic compound, while CdS-NiS-GR was employed for H evolution from water with sacrificial agents. AgBr-0.2%(MoS /1%GR) exhibited the best activity -1 with a degradation rate constant of 1.68 h, which was 2.6 times of pure AgBr. -1 The best reaction condition was pH=5 with a catalyst dosage of 1 g L . The photocatalyst was able to retain its activity after 4 consecutive cycles of the degradation tests, indicating a good stability for practical applications. CdS-10%NiS-0.25%GR achieved the highest specific hydrogen evolution rate at -1 -1 up to 29.8 mmol g h, which was 4.8 times of pristine CdS. The best reaction -1 condition was at pH=1.5 with a catalyst dosage of 0.1 g L . The catalyst also appeared to be rather stable, with less than 7% of the activity lost after 3 runs. Similar improvements could be observed under both solar light and visible light irradiations. The improvements in reactivity of the composite photocatalysts were also proven by the transient photocurrent response results that AgBr-0.2%(MoS /1%GR) and CdS-10%NiS-0.25%GR showed 2.5 times and 4 times higher photocurrent values of the pure main catalysts, respectively. According to the photocatalytic reaction mechanisms, it is argued that coupling with MoS /GR

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