Year

2019

Degree Name

Doctor of Philosophy

Department

School of Physics

Abstract

With ever-increasing concern about energy crisis, environmental pollution, and climate change, seeking for clean and renewable energy sources has become one of the biggest challenges for the sustainable development of society. The key to address this concern is the development of advanced energy conversion technologies, such as water electrolysis for hydrogen generation, fuel cells, and metal-air batteries. Developing high-efficient electrocatalysts for the next-generation energy conversion devices has become a primary focus of research. Since two-dimensional (2D) graphene was discovered, numerous 2D nanomaterials have aroused more research interest in the fields of energy conversion and storage. In particular, the novel 2D nanomaterials have become one of the most promising components for design and development of heterogenous electrocatalysts because of their unique physicochemical properties and adjustable electronic structure. However, some 2D nanomaterials are not active enough because of the large reaction free energy, low amount of active sites or poor conductivity. Some 2D materials are inert for electrocatalysis reactions, but are able to work as the functional substrates for the development of hybrid electrocatalysts. Thus, specific strategies are urgently desired to modulate the physicochemical and surface/interface properties of 2D material-based electrocatalysts, and to make full use of the functionalities of functional 2D material substrates to achieve fast catalytic reaction kinetics. In this regard, hetero-interface engineering strategy has been deployed into designing and preparing three different 2D material-based elctrocatalysts with well-defined interfaces for the enhanced oxygen evolution reaction (OER), hydrogen evolution reaction (HER), and oxygen reduction reaction (ORR). For the first work, the superhydrophilic GCN/Ni(OH)2 (GCNN) heterostructures with monodispersed Ni(OH)2 nanoplates strongly anchored on GCN were synthesized for enhanced water oxidation catalysis. Owing to the superhydrophilicity of functionalized GCN, the surface wettability of GCNN (contact angle 0°) was substantially improved as compared with bare Ni(OH)2 (contact angle 21°). Besides, GCN nanosheets can effectively suppress Ni(OH)2 aggregation to help expose more active sites. Benefiting from the well-defined catalyst surface, the optimal GCNN hybrid showed a significantly enhanced electrochemical performance over bare Ni(OH)2 nanosheets, although GCN is electrochemically inert. In addition, similar performance promotion resulting from wettability improvement induced by the incorporation of hydrophilic functionalized GCN was also successfully demonstrated on Co(OH)2...

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Unless otherwise indicated, the views expressed in this thesis are those of the author and do not necessarily represent the views of the University of Wollongong.