Functional metal oxide based heterostructures : design, synthesis and application to electrochemical energy storage

• Main Author: Zhou, Wei Wei
• Other Authors: Yu Ting
• Format: Theses and Dissertations
• Language: English
• Published: 2013
• Subjects: DRNTU::Science::Physics::Descriptive and experimental mechanics
• Online Access: https://hdl.handle.net/10356/51162
• Institution: Nanyang Technological University

One sparkling success of current nanoscale science and technology is reflected in the improving capability of engineering individual units and their spatial arrangements of functional materials and devices down to nanometer level. Integrating different nanocrystals with distinct properties into a single subject represents a promising way to achieve this goal. In this thesis, we have designed and prepared various metal oxide based heterostructures for electrochemical energy storage devices. SnO2 and Fe2O3, two of the most studied functional semiconductors, have been widely applied in photocatalytic degradation, gas sensing and lithium-ion batteries (LIBs). Recently, many studies have revealed that the physical performances of SnO2 or Fe2O3 can be remarkably improved by forming Fe2O3/SnO2 heterostructures. Inspired by this, we have developed two types of novel heterostructures by incorporating SnO2 and Fe2O3 as building blocks, and investigated their corresponding lithium storage performance. The first example is based on grafting 1D SnO2 nanorods onto both sides of pre-grown 2D Fe2O3 nanoflakes, forming a comb-like branched heterostructure. The overall synthetic procedure involves only two steps: direct heating the Fe foil in air for the preparation of Fe2O3 nanoflake stems, and the subsequent hydrothermal epitaxial growth of SnO2 nanorod branches. The other type of novel branched -Fe2O3/SnO2 heterostructure with six-fold-symmetry is prepared by combining a vapor transport deposition and a facile hydrothermal method. While the tree-like branched structures have been reported previously, to our knowledge, it is the first report on the synthesis of high-symmetry branched heterostructures where the SnO2 core nanowires are surrounded by ordered -Fe2O3 nanorod branches. When such composite SnO2/Fe2O3 heterostructures are tested as LIB anodes, an enhanced electrochemical performance compared to individual components is obtained, which can be ascribed to the unique 3D structure and the synergistic effects induced by both constituents.