TY - JOUR

T1 - The FeIV-O• oxyl unit as a key intermediate in water oxidation on the FeIII-hydroxide

T2 - DFT predictions

AU - Shubin, Aleksandr A.

AU - Kovalskii, Viktor Yu

AU - Ruzankin, Sergey Ph

AU - Zilberberg, Igor L.

AU - Parmon, Valentin N.

AU - Tomilin, Felix N.

AU - Avramov, Pavel V.

N1 - Funding Information: Aleksandr A. Shubin, Igor L. Zilberberg, and Valentin N. Parmon acknowledge the support of Russian Foundation for Basic Research under grant No. 15‐29‐01275. Viktor Yu. Kovalskii acknowledges the support of Russian Foundation for Basic Research under grant No. 18‐33‐00932. Calculations have been performed at the Siberian Supercomputer Centre SB RAS. Publisher Copyright: © 2021 Wiley Periodicals LLC Copyright: Copyright 2021 Elsevier B.V., All rights reserved.

PY - 2021/5/15

Y1 - 2021/5/15

N2 - 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. The “initial” vertex FeIII(OH) moiety forms this intermediate at the calculated overpotential of 0.93 V by adding one water molecule and withdrawing two proton–electron pairs. 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.

AB - 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. The “initial” vertex FeIII(OH) moiety forms this intermediate at the calculated overpotential of 0.93 V by adding one water molecule and withdrawing two proton–electron pairs. 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.

KW - negative spin density

KW - oxyl oxygen

KW - the FeOOH hydroxide

KW - the O-O coupling

KW - water oxidation

UR - http://www.scopus.com/inward/record.url?scp=85100536364&partnerID=8YFLogxK

U2 - 10.1002/qua.26610

DO - 10.1002/qua.26610

M3 - Article

AN - SCOPUS:85100536364

VL - 121

JO - International Journal of Quantum Chemistry

JF - International Journal of Quantum Chemistry

SN - 0020-7608

IS - 10

M1 - e26610

ER -