Design and fabrication of scalable, efficient and durable graphene-based catalysts for the water-soluble aromatic pollutant reduction

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Design and fabrication of scalable, efficient and durable graphene-based catalysts for the water-soluble aromatic pollutant reduction

 

Author: Hu, Huawen
Title: Design and fabrication of scalable, efficient and durable graphene-based catalysts for the water-soluble aromatic pollutant reduction
Degree: Ph.D.
Year: 2015
Subject: Graphene -- Synthesis.
Aromatic compounds -- Synthesis.
Hong Kong Polytechnic University -- Dissertations
Department: Institute of Textiles and Clothing
Pages: xx, 271 pages : color illustrations
Language: English
InnoPac Record: http://library.polyu.edu.hk/record=b2827750
URI: http://theses.lib.polyu.edu.hk/handle/200/8286
Abstract: This study explores different kinds of graphene-based catalysts for the reduction of aromatic pollutants with focus on widely used aromatic dye and nitro compounds. Graphene oxide (GnO)-derived graphene materials play a crucial role in the catalyst synthesis. The study is divided primarily into four research systems: (i) fabrication and analysis of a functionalized graphene as a promising catalyst support, (ii) use of the as-fabricated graphene, combined with an organic polymer network, to design and fabricate a highly efficient, durable and easily recyclable metal-based multicomponent composite catalyst with a monolithic structure, (iii) design and fabrication of a highly efficient and reusable non-noble metal-based multicomponent composite catalyst with an assembly structure, and (iv) development of an active and durable metal-free graphene-based carbocatalyst. Specifically, a low-temperature thermal functionalization strategy was applied to large-scale, cost-effective fabrication of the functionalized graphene in the first research system. The structure of the functionalized graphene was studied in depth through various characterization analyses combined with surface modification investigation. A multicomponent composite catalyst was subsequently fabricated by exploiting the thermally functionalized graphene as the metal catalyst support, with the assistance of a polyacrylamide network employed to render the composite catalyst durable and easily recyclable. The graphene component played a crucial role in the composite catalyst synthesis and in subsequent catalytic reactions. Both high efficiency and durability of the composite catalyst were achieved, along with an easily handling property. In the third research system, the study was extended to the other high-performance composite catalyst based on catecholamine chemistry. Mussel-inspired modification and functionalization enabled the reduction of GnO and in the meanwhile incorporation of numerous binding sites onto the graphene surfaces, facilitating the subsequent immobilization and stabilization of a non-noble metal nanocatalyst. The resulting ternary composite catalyst was demonstrated to be highly active and reusable in the reduction reactions, making it a promising lower-cost alternative to many reported noble metal-based composite catalysts. Finally, the study was devoted to fabrication and analysis of a series of GnO-based carbocatalysts using eco-friendly L-ascorbic acid (LAA) to mediate the intrinsic catalytic activity of GnO. Special emphasis was placed on the mechanistic understanding of the carbocatalytic reduction of 4-nitrophenol at the molecular level. An efficient, and impressively stable and durable LAA-mediated graphene carbocatalyst with an optimized structure was also produced for catalyzing the 4-nitrophenol reduction. The research work presented in this thesis provided different kinds of efficient and reusable graphene-based catalytic alternatives to the reported hydrogenation catalysts for the aromatic pollutant reduction. The overall simple fabrication processes for the present graphene-based catalysts can also facilitate their future industrial-scale production and applications, thus indicating that tangible benefits will probably be brought to the environment, energy and resource conservation, and economy. More importantly, the mechanistic insights into the catalytic reduction reactions over the present metal-based composite catalysts and metal-free graphene carbocatalysts will shed light on the future rational design and fabrication of highly efficient and durable graphene-based catalysts at the molecular level for many kinds of synthetic transformations, especially hydrogenation reactions.

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