| Summary: | 博士 === 國立中央大學 === 化學學系 === 105 === ENGLISH ABSTRACT
Regarded as future alternatives for Lithium ion batteries (LIBs), Sodium ion batteries (SIBs) have received tremendous attention during the last five years, mainly due to the worldwide abundance of Na and the significant cost-effective advantages. However, the development of suitable anode materials for Na-ion batteries remains a considerable challenge in view of the larger ionic radius of Na+ with respect to Li+ which leads to a higher volume expansion upon cycling and lower gravimetric and volumetric energy densities. This doctoral work aims to address these problems by designing nanomaterials with high power performance. Herein, a series of nanostructured materials specifically copper oxide (CuO) with different morphology: nanorod, nano ellipsoid and nano flakes structure were developed. By using X-ray diffraction, TEM and Ex-situ XRD observation techniques, the relationship between the electrode crystal structure and electrochemical performance was established.
In addition, to overcome the traditional problems, development of new carbonaceous materials with favourable structural properties, such as morphology, crystallinity, and porosity, as ideal carbon matrices for the high performance of SIBs is highly desirable. The pore arrangements affect their electrochemical behavior such as capacity, cycle efficiency, and rate capability. Different mesopore arrangements of ordered mesoporous carbons (OMCs) might have significant influences on the Na+ ion transport properties. OMCs like CMK-3 and CMK-8 were synthesized by nano casting method and a systematic analysis was carried out in order to understand the effect of key structural parameters of CMK-3 and CMK-8, on their electrochemical performances in SIBs in their pure forms without incorporation of metal oxides. The combined use of nanostructured transition metal oxides with OMCs could be an effective approach to solve the issues of anode materials for SIBs. Especially, CMK-3 and CMK-8 can be regarded as an excellent backbone and highly conductive matrices for CuO nanoparticles. To achieve the requirements for high power SIB, a hydrothermal synthesis method was applied to prepare CuO@CMK-3 and CuO@CMK-8 nanocomposites. Both the CuO@CMK-3 and CuO@CMK-8 anode materials were characterized by a variety of techniques to evaluate their structural and electrochemical properties. Direct experimental evidence provides a deep insight to the conversion reaction mechanism during the electrochemical sodiation/de-sodiation process for the CuO@CMK-3 and CuO@CMK-8 systems. Furthermore, fundamental scientific elucidation of the difference in transport and kinetic behaviors between different pore architecture based CuO@CMK electrodes, Na insertion/extraction mechanism, the reaction mechanism at solid electrolyte interphase (SEI) layer on the electrodes, charge transfer in the electrolyte-electrode interface and Na+ ion transport through the SEI layer was studied in detail. As a promising anode material, the as-prepared CuO@CMK-8 nanocomposite exhibited a high reversible sodium storage capacity and excellent cyclalibilty for SIB.
The second objective of this doctoral thesis is to develop efficient photocatalysts via simple and practical synthesis methods for catalytic application such as reduction of 4- nitrophenol and photocatalytic hydrogen generation. In this regard, different Copper based metal/metal oxide and ordered mesoporous carbon composite such as Cu@CMK-8 CuO@CMK-8 and Cu2O@CMK-8 photocatalysts were fabricated and characterized. Furthermore, the comparative performance of such photocatalysts for reduction of nitrophenol reaction were evaluated. In order to study the performance of a non-noble metal co-catalyst-semiconductor heterostructure for reduction of 4-nitrophenol as well as photocatalytic hydrogen generation, TiO2 with CMK-8 composite denoted as TiO2@CMK-8 was developed by a facile hydrothermal technique. Then, Ni-TiO2@CMK-8 was synthesized by a wet impregnation method followed by calcination at a reducing atmosphere. It was observed that the synergistic interactions between the Ni co-catalyst and the CMK-8 within the Ni-TiO2@CMK-8 composite substantially improves the solar photocatalytic hydrogen generation as well as the reduction of nitrophenol. A systematic analysis was carried out to investigate the effect of non-noble metal co-catalyst and ordered mesoporous carbon to maximize the photocatalytic hydrogen generation under solar light irradiation and catalytic reduction of nitrophenol.
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