Please use this identifier to cite or link to this item: https://hdl.handle.net/20.500.14279/33231
Title: Experimental and Theoretical Investigation of the Mechanism of the Reduction of O2 from Air to O22- by VIVO2+-N,N,N-Amidate Compounds and Their Potential Use in Fuel Cells
Authors: Papanikolaou, Michael G. 
Hadjithoma, Sofia 
Keramidas, Odysseas 
Drouza, Chryssoula 
Amoiridis, Angelos 
Themistokleous, Alexandros 
Hayes, Sofia C. 
Miras, Haralampos N. 
Lianos, Panagiotis 
Tsipis, Athanassios C. 
Kabanos, Themistoklis A. 
Keramidas, Anastasios D. 
Major Field of Science: Engineering and Technology
Field Category: Chemical Engineering
Keywords: Nuclear magnetic resonance spectroscopy;Electron spin resonance spectroscopy;Cyclic voltammetry;Fuel cells;Ligands;Nuclear magnetic resonance;Vanadium compounds;Reaction intermediates;Paramagnetic resonance;Oxidation
Issue Date: 5-Feb-2024
Source: Inorganic chemistry, 2024, vol. 63, no. 7
Volume: 63
Issue: 7
Journal: Inorganic Chemistry 
Abstract: The two-electron reductive activation of O2 to O22- is of particular interest to the scientific community mainly due to the use of peroxides as green oxidants and in powerful fuel cells. Despite of the great importance of vanadium(IV) species to activate the two-electron reductive activation of O2, the mechanism is still unclear. Reaction of VIVO2+ species with the tridentate-planar N,N,N-carboxamide (ΗL) ligands in solution (CH3OH:H2O) under atmospheric O2, at room temperature, resulted in the quick formation of [VV(═O)(η2-O2)(κ3-L)(H2O)] and cis-[VV(═O)2(κ3-L)] compounds. Oxidation of the VIVO2+ complexes with the sterically hindered tridentate-planar N,N,N-carboxamide ligands by atmospheric O2 gave only cis-[VV(═O)2(κ3-L)] compounds. The mechanism of formation of [VV(═O)(η2-O2)(κ3-L)(H2O)] (I) and cis-[VV(═O)2(κ3-L)] (II) complexes vs time, from the interaction of [VIV(═O)(κ3-L)(Η2Ο)2]+ with atmospheric O2, was investigated with 51V, 1H NMR, UV-vis, cw-X-band EPR, and 18O2 labeling IR and resonance Raman spectroscopies revealing the formation of a stable intermediate (Id). EPR, MS, and theoretical calculations of the mechanism of the formation of I and II revealed a pathway, through a binuclear [VIV(═O)(κ3-L)(H2O)(η1,η1-O2)VIV(═O)(κ3-L)(H2O)]2+ intermediate. The results from cw-EPR, 1H NMR spectroscopies, cyclic voltammetry, and the reactivity of the complexes [VIV(═O)(κ3-L)(Η2Ο)2]+ toward O2 reduction fit better to an intermediate with a binuclear nature. Dynamic experiments in combination with computational calculations were undertaken to fully elucidate the mechanism of the O2 reduction to O22- by [VIV(═O)(κ3-L)(Η2Ο)2]+. The galvanic cell {Zn|VIII,VII||Id, [VIVO(κ3-L)(H2O)2]+|O2|C(s)} was manufactured, demonstrating the important applicability of this new chemistry to Zn|H2O2 fuel cells technology generating H2O2 in situ from the atmospheric O2.
URI: https://hdl.handle.net/20.500.14279/33231
ISSN: 00201669
DOI: 10.1021/acs.inorgchem.3c03272
Rights: Attribution-NonCommercial-NoDerivatives 4.0 International
Type: Article
Affiliation : University of Cyprus 
Cyprus University of Technology 
University of Glasgow 
University of Patras 
Funding: Research Promotion Foundation of Cyprus
Publication Type: Peer Reviewed
Appears in Collections:Άρθρα/Articles

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