title: In situ X-ray absorption near edge structure studies and charge transfer kinetics of Na6[V10O28] electrodes.
abstract: Polyoxometalates (POMs) have been reported as promising electrode materials for energy storage applications due to their ability to undergo fast redox reactions with multiple transferred electrons per polyanion. Here we employ a polyoxovanadate salt, Na6[V10O28], as an electrode material in a lithium-ion containing electrolyte and investigate the electron transfer properties of Na6[V10O28] on long and short timescales. Looking at equilibrated systems, in situ V K-edge X-ray absorption near edge structure (XANES) studies show that all 10 V5+ions in Na6[V10O28] can be reversibly reduced to V4+in a potential range of 4-1.75 V vs. Li/Li+. Focusing on the dynamic response of the electrode to potential pulses, the kinetics of Na6[V10O28] electrodes and the dependence of the fundamental electron transfer rate k0on temperature are investigated. From these measurements we calculate the reorganization energy and compare it with theoretical predictions. The experimentally determined reorganization energy of λ = 184 meV is in line with the theoretical estimate and confirms the hypothesis of small values of λ for POMs due to electrostatic shielding of the redox center from the solvent.
authors.affiliation: TUM CREATE, 1 CREATE Way, #10-02 CREATE Tower, 138602 Singapore. Ulrich.Stimming@newcastle.ac.uk madhavi@ntu.edu.sg and Department of Chemistry, Technische Universität München, Lichtenbergstraße 4, 85748 Garching, Germany and School of Materials Science and Engineering, Nanyang Technological University, 639798 Singapore and Department of Materials Science and Engineering, National Tsing Hua University, 101, Sec. 2, Kuang-Fu Road, Hsinchu 30013, Taiwan.
authors.forename: Han-Yi
authors.identifier: http://orcid.org/0000-0001-8146-7101
authors.initials: HY
authors.lastname: Chen
authors.affiliation: TUM CREATE, 1 CREATE Way, #10-02 CREATE Tower, 138602 Singapore. Ulrich.Stimming@newcastle.ac.uk madhavi@ntu.edu.sg and School of Chemistry, Bedson Building, Newcastle University, Newcastle upon Tyne NE1 7RU, UK.
authors.forename: Jochen
authors.initials: J
authors.lastname: Friedl
authors.affiliation: Department of Chemical Engineering, National Taiwan University of Science and Technology (NTUST), Taipei 106, Taiwan. bjh@mail.ntust.edu.tw.
authors.forename: Chun-Jern
authors.initials: CJ
authors.lastname: Pan
authors.affiliation: Department of Life Sciences and Chemistry, Jacobs University, P.O. Box 750561, 28725 Bremen, Germany.
authors.forename: Ali
authors.initials: A
authors.lastname: Haider
authors.affiliation: Department of Life Sciences and Chemistry, Jacobs University, P.O. Box 750561, 28725 Bremen, Germany.
authors.forename: Rami
authors.initials: R
authors.lastname: Al-Oweini
authors.affiliation: School of Materials Science and Engineering, Nanyang Technological University, 639798 Singapore and Energy Research Institute@NTU (ERI@N), Research Techno Plaza, 50 Nanyang Drive, 637553 Singapore.
authors.forename: Yan Ling
authors.initials: YL
authors.lastname: Cheah
authors.affiliation: Department of Chemical Engineering, National Taiwan University of Science and Technology (NTUST), Taipei 106, Taiwan. bjh@mail.ntust.edu.tw.
authors.forename: Ming-Hsien
authors.initials: MH
authors.lastname: Lin
authors.affiliation: Department of Life Sciences and Chemistry, Jacobs University, P.O. Box 750561, 28725 Bremen, Germany.
authors.forename: Ulrich
authors.initials: U
authors.lastname: Kortz
authors.affiliation: Department of Chemical Engineering, National Taiwan University of Science and Technology (NTUST), Taipei 106, Taiwan. bjh@mail.ntust.edu.tw and National Synchrotron Radiation Research Center (NSRRC), Hsinchu 30076, Taiwan.
authors.forename: Bing-Joe
authors.identifier: http://orcid.org/0000-0002-3873-2149
authors.initials: BJ
authors.lastname: Hwang
authors.affiliation: TUM CREATE, 1 CREATE Way, #10-02 CREATE Tower, 138602 Singapore. Ulrich.Stimming@newcastle.ac.uk madhavi@ntu.edu.sg and School of Materials Science and Engineering, Nanyang Technological University, 639798 Singapore and Energy Research Institute@NTU (ERI@N), Research Techno Plaza, 50 Nanyang Drive, 637553 Singapore.
authors.forename: Madhavi
authors.initials: M
authors.lastname: Srinivasan
authors.affiliation: TUM CREATE, 1 CREATE Way, #10-02 CREATE Tower, 138602 Singapore. Ulrich.Stimming@newcastle.ac.uk madhavi@ntu.edu.sg and Department of Chemistry, Technische Universität München, Lichtenbergstraße 4, 85748 Garching, Germany and School of Chemistry, Bedson Building, Newcastle University, Newcastle upon Tyne NE1 7RU, UK.
authors.forename: Ulrich
authors.initials: U
authors.lastname: Stimming