TY - JOUR

T1 - Photoelectrochemistry of Ferrites

T2 - Theoretical Predictions vs. Experimental Results

AU - Ulpe, A.C.

AU - Bauerfeind, K.C.L.

AU - Granone, L.I.

AU - Arimi, A.

AU - Megatif, L.

AU - Dillert, R.

AU - Warfsmann, S.

AU - Taffa, D.H.

AU - Wark, M.

AU - Bahnemann, D.W.

AU - Bredow, T.

N1 - Funding information: We gratefully acknowledge financial support by the Deutsche Forschungsgemeinschaft within the priority program SPP 1613 ‘Fuels Produced Regeneratively Through Light-Driven Water Splitting: Clarification of the Elemental Processes Involved and Prospects for Implementation in Technological Concepts’ (BR 1768/9-1, BA 1137/22-1, WA 1116/28). The authors A. Ulpe, K. C. L. Bauerfeind and T. Bredow thank the Paderborn Center for Parallel Computing, PC2, and the Leibniz University IT Services (former Regionales Rechenzentrum für Niedersachsen [RRZN]) for providing computational resources. A. Ulpe thankfully acknowledges the financial support by the International Max Planck Research School on Reactive Structure Analysis for Chemical Reactions (IMPRS-RECHARGE).

PY - 2020/4/28

Y1 - 2020/4/28

N2 - This paper gives an overview about recent theoretical and experimental work on electronic and optical properties of spinel ferrites MFe 2O 4. These compounds have come into focus of research due to their possible application as photocatalyst material for photoelectrochemical water splitting. The theoretical background of state-of-the-art quantum-chemical approaches applied for predicting electronic and optical band gaps, absolute band positions, optical absorption spectra, dielectric functions and Raman spectra, is briefly reviewed. Recent applications of first-principles methods on magnetic and electronic properties of ferrites with M = Mg and the first row of subgroup elements Sc to Zn are presented, where it is shown that the fundamental band gap is strongly dependent on the spin state and the degree of inversion of the spinel structure. The observed variation of electronic properties may serve as an explanation for the large scattering of experimental results. The exchange of M and Fe cations has also a pronounced effect on the Raman spectra of ferrites, which is analyzed at atomic scale from first principles. Calculated optical absorption spectra of ferrites are compared to experimental spectra. The electronic nature of the first excitations and the role of oxygen vacancies are discussed. For the calculation of absolute band positions, which have a significant impact on the photoelectrochemical activity of the ferrites, models of the most stable ferrite surfaces are developed that take into account their polar nature and the interaction with the solvent. Theoretically predicted valence and conduction band edges are compared to results from electrochemical measurements. The role of cation exchange on the surface electronic structure is investigated both theoretically and experimentally.

AB - This paper gives an overview about recent theoretical and experimental work on electronic and optical properties of spinel ferrites MFe 2O 4. These compounds have come into focus of research due to their possible application as photocatalyst material for photoelectrochemical water splitting. The theoretical background of state-of-the-art quantum-chemical approaches applied for predicting electronic and optical band gaps, absolute band positions, optical absorption spectra, dielectric functions and Raman spectra, is briefly reviewed. Recent applications of first-principles methods on magnetic and electronic properties of ferrites with M = Mg and the first row of subgroup elements Sc to Zn are presented, where it is shown that the fundamental band gap is strongly dependent on the spin state and the degree of inversion of the spinel structure. The observed variation of electronic properties may serve as an explanation for the large scattering of experimental results. The exchange of M and Fe cations has also a pronounced effect on the Raman spectra of ferrites, which is analyzed at atomic scale from first principles. Calculated optical absorption spectra of ferrites are compared to experimental spectra. The electronic nature of the first excitations and the role of oxygen vacancies are discussed. For the calculation of absolute band positions, which have a significant impact on the photoelectrochemical activity of the ferrites, models of the most stable ferrite surfaces are developed that take into account their polar nature and the interaction with the solvent. Theoretically predicted valence and conduction band edges are compared to results from electrochemical measurements. The role of cation exchange on the surface electronic structure is investigated both theoretically and experimentally.

KW - DFT

KW - perturbation theory

KW - photoelectrochemical water splitting

KW - spectroscopy

KW - spinel ferrites

UR - http://www.scopus.com/inward/record.url?scp=85078100671&partnerID=8YFLogxK

U2 - 10.1515/zpch-2019-1449

DO - 10.1515/zpch-2019-1449

M3 - Article

VL - 234

SP - 719

EP - 776

JO - Zeitschrift fur Physikalische Chemie

JF - Zeitschrift fur Physikalische Chemie

SN - 0044-3336

IS - 4

ER -