Metal sulfides for electrochemical energy storage and conversion
Date of Issue2017-03-15
Interdisciplinary Graduate School (IGS)
Energy Research Institute @ NTU (ERI@N)
Electrochemical energy storage and conversion devices are regarded as one of the most attractive technologies to overcome the crisis of fossil fuel exhaustion and the global pollution. The key to advance these technologies is to explore suitable materials with various advantages of good performance, such as high stability, low cost, and environmental friendliness. The emerging two-dimensional (2D) molybdenum sulfide (MoS2) has shown vast potential for renewable energy storage and conversion applications, due to its intriguing physicochemical properties. Nevertheless, several issues handicap the commercial application of MoS2, including rapid structure degradation, low electrical conductivity, and sluggish charge transfer kinetics. Therefore, scientific research and breakthroughs are highly desirable to address these issues and satisfy the requirements for practical use. The main aim of this thesis is to investigate MoS2-based composites with engineered nanostructures as prospective electrodes for energy storage and conversion devices with good performance, high stability, and excellent safety. By virtue of the scrupulous design and smart hybridization of nanoarchitectures, exceptional properties and performance could be achieved. With this in view, novel MoS2/Ni3S2 heterostructures, flexible MoS2 electrodes supported on different substrates and hierarchical MoS2 hollow nanotubes have been developed and designed by facile synthetic routes. Meanwhile, the effect of different nanostructures on the electrochemical performance of energy storage and conversion devices is fundamentally investigated to provide in-depth studies on the relationship between structure and performance. The relevant studies in the thesis are divided into five parts, including Ni3S2@MoS2 core/shell nanorod arrays on Ni foam as the supercapacitor electrode (Chapter 4), honeycomb-like MoS2 nanoarchitectures anchored into graphene foam (GF) for enhanced lithium storage (Chapter 5), MoS2 architectures supported on graphene foam/carbon nanotube (GF/CNT) hybrid films: highly integrated frameworks with ideal contact for superior lithium storage (Chapter 6), MoS2 nanosheets decorated Ni3S2@MoS2 coaxial nanofibers for enhanced Na-ion storage (Chapter 7) and active sites–enriched hierarchical MoS2 nanotubes: highly active and stable architecture for boosting hydrogen evolution and lithium storage (Chapter 8). As the in-depth understanding of electrochemical reaction mechanisms is significant for advancing different energy storage and conversion devices, this thesis also performs the fundamental investigation of the lithium/sodium storage mechanisms, and the mechanisms of hydrogen evolution reaction (HER). The cause for enhanced performance has been also carefully explored. It is hoped that all these studies could shed more light on the fundamental understanding.