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Paul Avramov
Public Documents
2
The FeIV-O● oxyl unit as a key intermediate in water oxidation on the FeIII-hydroxide...
Alexander Shubin
and 6 more
June 02, 2020
The O-O coupling process in water oxidation on the gamma FeOOH hydroxide catalyst is simulated by means of density functional theory using model iron cubane cluster Fe4O4(OH)4. A key reactive intermediate is proposed to be the HO-FeIV-O• oxyl unit with terminal oxo radical formed from vertex HO-FeIV-OH moiety by withdrawal of proton-electron pair. The O-O coupling goes via water nucleophilic attack on the oxyl oxygen to form the O-O bond with a remarkably low barrier of 11 kcal/mol. This process is far more effective than alternative scenario based on direct interaction of two ferryl FeIV=O sites (with estimated barrier of 36 kcal/mol) and is comparable with the coupling between terminal oxo center and three-coordinated lattice oxo center (12 kcal/mol barrier). The process of hydroxylation of terminal oxygen inhibits the O-O coupling. Nevertheless, being more effective for ferryl oxygen, the hydroxylation in fact enhances selectivity of the O-O coupling initiated by the oxyl oxygen.
Fe-porphyrine complex atop of armchair graphene nanoribbon: multiplicity, coordinatio...
Iuliia Melchakova
and 2 more
April 06, 2020
The atomic structure, spin states of the interface based on iron-porphyrin and armchair graphene nanoribbon (FeP/AGNR) and potential energy surface of FeP atop of AGNR migration is investigated via DFT theory. The multiplicity of Fe ion in iron porphyrin for all possible types of coordination is determined as a triplet. It is estimated that FeP would place atop AGNR at the position where two Fe-N bonds are located above the C-C bond, another two are located above C atoms. The barrier of migration of iron porphyrin complex atop of graphene armchair nanoribbon is found to be smaller the temperature factor, making the heterostructure to be in temperature equilibrium between different types of coordination of the iron porphyrin atop of graphene nanoribbon