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An electrochemical impedance study of alkaline water splitting using nickel (iron) oxides nanosheets
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.ORCID iD: 0000-0002-7892-5260
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry. Northwestern Polytechnical University.
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials. Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.ORCID iD: 0000-0002-8279-5163
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry. Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics. Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.ORCID iD: 0000-0003-2759-7356
(English)In: Article in journal (Refereed) Submitted
National Category
Physical Chemistry Other Chemistry Topics Inorganic Chemistry
Identifiers
URN: urn:nbn:se:uu:diva-380523OAI: oai:DiVA.org:uu-380523DiVA, id: diva2:1300271
Available from: 2019-03-28 Created: 2019-03-28 Last updated: 2019-03-29
In thesis
1. Transition Metal-Based Electrocatalysts for Alkaline Water Splitting and CO2 Reduction
Open this publication in new window or tab >>Transition Metal-Based Electrocatalysts for Alkaline Water Splitting and CO2 Reduction
2019 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

With excessive usage of fossil fuels and ever-increasing environmental issues, numerous efforts have been devoted to the development of renewable energies for the replacement of traditional fossil fuels to reduce greenhouse gas emission and realize the rapidly growing demand for global energy. Renewable energies, however, often show diurnal and seasonal variations in power output, forming a need for energy storage to meet people’s continuous energy supply. One approach is to use electrolysis and produce a fuel that can be used on demand at a later stage. A full realization of effective electricity-to-fuel conversion, however, is still limited by the large overpotential requirements as well as concerns with the usage of scarce platinum group elements. This thesis presents studies on transition metal-based electrocatalysts for alkaline water splitting and CO2 reduction, which are two technologies to produce a chemical fuel from renewable electricity. Our aim is to develop efficient, inexpensive, and robust electrocatalysts based on earth-abundant elements with high energy conversion efficiencies.

In the first part, we develop and investigate three different electrocatalysts intended for high-performance electrocatalysis of water; NiO nanoflakes (NFs) with tuneable surface morphologies, Fe doped NiO nanosheets (NSs), and self-optimized NiFe layered double hydroxide (LDH) NSs. The self-assembled NiO NFs show drastically different performance for the oxygen evolution reaction (OER). Besides the morphology effect on the catalytic property, the presence of Fe is also functional to improve the catalytic activity for both OER and hydrogen evolution reaction (HER). The NiFe LDH NSs form the most effective system for the overall catalytic performance and is dramatically improved via a dynamic self-optimization, especially for HER, where the overpotential decreases from 206 mV to 59 mV at 10 mA cm-2. In order to get insight into the interfacial reaction processes, a variety of techniques were performed to explore the underlying reasons for the catalytic improvement. Ex-situ X-ray photoelectron spectroscopy, transmission electron microscope and in-situ Raman spectroscopy were utilized to characterize and understand the oxidations states, the crystallinity and the active phases. Electrochemical impedance spectroscopy was applied to investigate the dominating reaction mechanisms during high-performance and stable electrocatalysis.

In the second part, dynamically formed CuInO2 nanoparticles were demonstrated to be high-performance electrocatalysts for CO2 reduction. In-situ Raman spectroscopy was utilized to reveal and understand the formation of CuInO2 nanoparticles based on the Cu2O pre-catalyst onto an interlayer of indium tin oxide under the electrochemical reaction. Density function theory calculation and ex-situ X-ray diffraction further prove the formation of CuInO2 nanoparticles during vigorous catalysis. The findings give important clues on how Cu-based electrocatalysts can be formed into more active materials and can provide inspiration for other Cu-based intermetallic oxides for high-efficiency CO2 reduction.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2019. p. 87
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1791
Keywords
Alkaline water splitting, CO2 reduction, Electrocatalyst, In-situ Raman spectroscopy.
National Category
Chemical Sciences Engineering and Technology
Research subject
Chemistry with specialization in Materials Chemistry
Identifiers
urn:nbn:se:uu:diva-380575 (URN)978-91-513-0620-9 (ISBN)
Public defence
2019-05-21, Polhemsalen, 10134, Ångström Laboratory, Lägerhyddsv. 1, Uppsala, 13:15 (English)
Opponent
Supervisors
Available from: 2019-04-29 Created: 2019-03-29 Last updated: 2019-06-18

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Qiu, ZhenMa, YueNiklasson, GunnarEdvinsson, Tomas

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