Dataset Information

Hazardous Doping for Photo-Electrochemical Conversion: The Case of Nb-Doped Fe?O? from First Principles.

ABSTRACT: The challenge of improving the efficiency of photo-electrochemical devices is often addressed through doping. However, this strategy could harm performance. Specifically, as demonstrated in a recent experiment, doping one of the most widely used materials for water splitting, iron (III) oxide (Fe?O?), with niobium (Nb) can still result in limited efficiency. In order to better understand the hazardous effect of doping, we use Density Functional Theory (DFT)+U for the case of Nb-doped Fe?O?. We find a direct correlation between the charge of the dopant, the charge on surface of the Fe?O? material, and the overpotential required for water oxidation reaction. We believe that this work contributes to advancing our understanding of how to select effective dopants for materials.

SUBMITTER: Yatom N

PROVIDER: S-EPMC6332189 | biostudies-literature | 2015 Nov

REPOSITORIES: biostudies-literature

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Hazardous Doping for Photo-Electrochemical Conversion: The Case of Nb-Doped Fe₂O₃ from First Principles.

Yatom Natav N Toroker Maytal Caspary MC

Molecules (Basel, Switzerland) 20151104 11

The challenge of improving the efficiency of photo-electrochemical devices is often addressed through doping. However, this strategy could harm performance. Specifically, as demonstrated in a recent experiment, doping one of the most widely used materials for water splitting, iron (III) oxide (Fe₂O₃), with niobium (Nb) can still result in limited efficiency. In order to better understand the hazardous effect of doping, we use Density Functional Theory (DFT)+U for the case of Nb-doped Fe₂O₃. We f ...[more]

PMID: 26556324

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Project description:We present here a computational study of reactions at a model complex of the SyrB2 enzyme active site. SyrB2, which chlorinates L-threonine in the syringomycin biosynthetic pathway, belongs to a recently discovered class of alpha-ketoglutarate (alphaKG), non-heme Fe(II)-dependent halogenases that share many structural and chemical similarities with hydroxylases. Namely, halogenases and hydroxylases alike decarboxylate the alphaKG co-substrate, facilitating formation of a high-energy ferryl-oxo intermediate that abstracts a hydrogen from the reactant complex. The reaction mechanisms differ at this point, and mutation of active site residues (Asp for the hydroxylase to Ala or Ala to Asp/Glu for halogenase) fails to reproduce hydroxylating activity in SyrB2 or halogenating activity in similar hydroxylases. Using a density functional theory approach with a recently implemented Hubbard U correction for accurate treatment of transition-metal chemistry, we explore probable reaction pathways and mechanisms via a model complex consisting of only the iron center and its direct ligands. We show that the first step, alphaKG decarboxylation, is barrierless and exothermic, but the subsequent hydrogen abstraction step has an energetic barrier consistent with that accessible under biological conditions. In the model complex we use, radical chlorination is barrierless and exothermic, whereas the analogous hydroxylation is found to have a small energetic barrier. The hydrogen abstraction and radical chlorination steps are strongly coupled: the barrier for the hydrogen abstraction step is reduced when carried out concomitantly with the exothermic chlorination step. Our work suggests that the lack of chlorination in mutant hydroxylases is most likely due to poor binding of chlorine in the active site, whereas mutant halogenases do not hydroxylate for energetic reasons. Although secondary shell residues undoubtedly modulate the overall reactivity and binding of relevant substrates, we show that a small model compound consisting exclusively of the direct ligands to the metal can help explain reactivity heretofore not yet understood in the halogenase SyrB2.

Dataset Information

Hazardous Doping for Photo-Electrochemical Conversion: The Case of Nb-Doped Fe?O? from First Principles.

Publications

Hazardous Doping for Photo-Electrochemical Conversion: The Case of Nb-Doped Fe₂O₃ from First Principles.

Similar Datasets

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