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Electrochemical imaging of energy conversion and storage materials
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Tao, Binglin (2020) Electrochemical imaging of energy conversion and storage materials. PhD thesis, University of Warwick.
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WRAP_Theses_Tao_J_2020.pdf - Submitted Version - Requires a PDF viewer. Download (9Mb) | Preview |
Official URL: http://webcat.warwick.ac.uk/record=b3714389~S15
Abstract
This thesis presents various functionalities of scanning electrochemical cell microscopy (SECCM) in the field of energy conversion and storage materials, via focusing on hydrogen evolution reaction (HER) catalysis at two-dimensional materials and Li-ion (de)intercalation at battery cathode materials (LiMn2O4). In the context of HER catalysis, through the use of local (spatially resolved) linear sweep voltammetry, the activity of hexagonal boron nitride (h-BN) nanosheets supported on different metal substrates (Cu and Au) are compared. Au-supported h-BN exhibited significantly enhanced HER charge-transfer kinetics (i.e., higher exchange current density) and a smaller Tafel slope compared to Cu-supported h-BN. These results demonstrate that the electronic interaction with the underlying metal substrate plays a significant role in modulating the electrocatalytic activity of h-BN. The same methodology has also been used to measure the intrinsic electrochemical properties of pristine MoS2/WS2 crystals. Catalytic activity for the HER is greatly enhanced at the macroscopic surface defects of these electrodes, measured directly where the active edge plane (e.g., crevices, holes, cracks, etc.), with single-layer sensitivity. Besides, nanometer-resolved measurements reveal previously unseen electrochemical phenomena at these electrodes, i.e., spatial activity variations on basal surface, attributed to localized minor structural deformities (e.g. mechanical strain and defect density) throughout the crystal. In the context of Li-ion (de)intercalation, using a correlative electrochemistry-microscopy method, the redox activity (reveals through cyclic voltammetry) of a series of individual LiMn2O4 particles is linked to their corresponding particle size, morphology, crystallinity, and other factors. It has been observed that subtle changes in particle form can greatly influence electrochemical properties of these nominally similar particles. Further spatially-resolved galvanostatic measurements prove that individual LiMn2O4 particles can be charge/discharged at superfast rate (more than 200 C, where 1C mean fully charge/discharge battery in one hour, 200 C means fully charge/discharge in 18 s). Finally, a series of SECCM probes with graded diameters was exploited to study the electrochemical behavior evolution from single LiMn2O4 particles to the LiMn2O4 agglomerates level. Precisely controlling the position of the micropipette in 3D space allowed the influence of ensemble effects and particle-support contact resistance on Li+ (de)intercalation kinetics to be studied separately, proving that the charge-transfer barrier in LiMn2O4 ensembles is largely dictated by interparticle interactions, while the nature of the particle-support contact (i.e., wet vs dry contact) also play an important role.
Item Type: | Thesis (PhD) | ||||
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Subjects: | Q Science > QD Chemistry Q Science > QH Natural history T Technology > TK Electrical engineering. Electronics Nuclear engineering |
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Library of Congress Subject Headings (LCSH): | Scanning electrochemical microscopy, Energy storage -- Materials -- Imaging, Energy conversion -- Materials -- Imaging, Hydrogen evolution reaction | ||||
Official Date: | September 2020 | ||||
Dates: |
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Institution: | University of Warwick | ||||
Theses Department: | Department of Chemistry | ||||
Thesis Type: | PhD | ||||
Publication Status: | Unpublished | ||||
Supervisor(s)/Advisor: | Unwin, Patrick R. | ||||
Sponsors: | University of Warwick | ||||
Format of File: | |||||
Extent: | xxix, 187 leaves : illustrations (some colour) | ||||
Language: | eng |
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