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Pt/α-MnO2 nanotube: a highly active electrocatalyst for Li-Obattery
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.ORCID iD: 0000-0003-2538-8104
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
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2014 (English)In: Nano Energy, ISSN 2211-2855, Vol. 10, 19-27 p.Article in journal (Refereed) Published
Abstract [en]

The preparation of α-MnO2 nanotubes (M-NT) decorated with platinum nanoparticles (Pt/M-NT) by a simple reduction and mechanical stirring method is presented in this work, which aims to design a highly active catalyst for the Li-O2 battery. The obtained samples were characterized by XRD, SEM, TEM, BET, and XPS techniques. The electrocatalytic performance of the prepared samples was evaluated by tracking the decomposition of Li2O2 during the charging process in a Li-O2 cell using in situ XRD and operando SR-PXD, which gave direct and time resolved information during the whole process. The results indicated that Pt nanoparticles were uniformly dispersed on the surface of M-NT. Even a small amount (1 wt%) of Pt on M-NT did largely enhance the kinetics of the charging process. A cell with 5 wt% Pt/M-NT showed the highest catalytic activity and lowest charging potential. The decomposition of Li2O2 during the charging process in a Li-O2 cell with 5 wt% Pt/M-NT followed a zero-order reaction. This promoting effect from the supported nanocatalyst can be attributed to the high surface area, highly dispersed and uniform Pt deposition, and proper surface state modifications.

Place, publisher, year, edition, pages
Elsevier, 2014. Vol. 10, 19-27 p.
Keyword [en]
Pt nanoparticle, MnO2 nanotube, Li-O2 battery, charging process, electrocatalysis, operando synchrotron-based XRD
National Category
Materials Chemistry
Research subject
Chemistry with specialization in Materials Chemistry
Identifiers
URN: urn:nbn:se:uu:diva-234462DOI: 10.1016/j.nanoen.2014.08.022ISI: 000345986500003OAI: oai:DiVA.org:uu-234462DiVA: diva2:756721
Funder
Swedish Research CouncilSwedish Energy Agency
Available from: 2014-10-18 Created: 2014-10-18 Last updated: 2016-04-21Bibliographically approved
In thesis
1. The O2 electrode performance in the Li-O2 battery
Open this publication in new window or tab >>The O2 electrode performance in the Li-O2 battery
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Li-O2 batteries have been attracting increasing attention and R&D efforts as promising power sources for electric vehicles (EVs) due to their significantly higher theoretical energy densities compared to conventional Li-ion batteries. The research presented in this thesis covers the investigation of factors influencing the decomposition of Li2O2, the development of highly active electrocatalysts, and the design of low-cost and easy-operation binder-free O2 electrodes for Li-O2 batteries. Being the main technique, SR-PXD was used both as a continuous light source to advance the electrochemical decomposition of Li2O2 under the X-ray illumination and an operando tool that allowed us to probe the degradation of Li2O2.

Since XRD was intensively used in my thesis work, the effect of X-ray irradiation on the stability of Li2O2 was studied. The accelerating effect of X-rays on the electrochemical decomposition of Li2O2 was, for the first time, explored. The electrochemical decomposition rate of Li2O2 was proportional to the X-ray intensity used. It is proposed that the decomposition might involve a three-step reaction with [Li2O2]x+ and Li2-xO2* as intermediates, which followed pseudo-zero-order kinetics. Then, three electrocatalysts (Pt/MNT, Ru/MNT and Li2C8H2O6) were developed, which exhibited good electrocatalytic performances during the OER. Their activities were evaluated by following the Li2O2 decomposition in electrodes during the charging processes. In addition, the time-resolved OER kinetics for the electrocatalyst-containing Li-O2 cells charged galvanostatically and potentiostatically was systematically investigated using operando SR-PXD. It was found that a small amount of Pt or Ru decoration on the MNTs enhanced the OER efficiency in a Li-O2 cell. The Li2O2 decomposition of an electrode with 5 wt% Pt/MNT, 2 wt% Ru/MNT or Li2C8H2O6 in a Li-O2 cell followed pseudo-zero-order kinetics. Finally, a novel binder-free NCPE for Li-O2 batteries was presented. It displayed a bird’s nest microstructure, which could provide the self-standing electrode with considerable mechanic durability, fast O2 diffusion and enough space for the discharge product deposition. The NCPE contained N-containing functional groups, which may promote the electrochemical reactions.

Place, publisher, year, edition, pages
Uppsala: Uppsala universitet, 2015. 73 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1271
Keyword
Li-oxygen battery, X-ray irradiation, Electrocatalyst, Synchrotron radiation powder X-ray diffraction, Time-resolved kinetics, Binder-free cathode, Bird’s nest microstructure.
National Category
Inorganic Chemistry
Identifiers
urn:nbn:se:uu:diva-259589 (URN)978-91-554-9294-6 (ISBN)
Public defence
2015-09-25, Häggsalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 13:15 (English)
Opponent
Supervisors
Available from: 2015-09-03 Created: 2015-08-09 Last updated: 2016-04-21

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