TY - JOUR

T1 - Effect of the Degree of Inversion on the Photoelectrochemical Activity of Spinel ZnFe2O4

AU - Granone, Luis I.

AU - Nikitin, Konstantin

AU - Emeline, Alexei

AU - Dillert, Ralf

AU - Bahnemann, Detlef W.

N1 - Funding information: Acknowledgments: The authors would like to thank Peter Behrens and Malte Schäfer (Institute for Inorganic Chemistry, Gottfried Wilhelm Leibniz University Hannover) for the physisorption measurements. The publication of this article was funded by the Open Access Fund of the Gottfried Wilhelm Leibniz Universität Hannover. This research was funded by the Deutsche Forschungsgemeinschaft (DFG) under the SPP 1613 program (BA 1137/22-1), the Niedersächsisches Ministerium fürWissenschaft und Kultur (NTH-research group “ElektroBak”), and the Korea government (MSIP) through NRF under the Global Research Laboratory program (2014K1A1A2041044). The authors would like to thank Peter Behrens and Malte Schäfer (Institute for Inorganic Chemistry, GottfriedWilhelm Leibniz University Hannover) for the physisorption measurements. The publication of this article was funded by the Open Access Fund of the Gottfried Wilhelm Leibniz Universität Hannover. Funding: This research was funded by the Deutsche Forschungsgemeinschaft (DFG) under the SPP 1613 program (BA 1137/22-1), the Niedersächsisches Ministerium für Wissenschaft und Kultur (NTH-research group “ElektroBak”), and the Korea government (MSIP) through NRF under the Global Research Laboratory program (2014K1A1A2041044).

PY - 2019/5

Y1 - 2019/5

N2 - Physicochemical properties of spinel ZnFe 2O 4 (ZFO) are known to be strongly affected by the distribution of the cations within the oxygen lattice. In this work, the correlation between the degree of inversion, the electronic transitions, the work function, and the photoelectrochemical activity of ZFO was investigated. By room-temperature photoluminescence measurements, three electronic transitions at approximately 625, 547, and 464 nm (1.98, 2.27, and 2.67 eV, respectively) were observed for the samples with different cation distributions. The transitions at 625 and 547 nm were assigned to near-band-edge electron-hole recombination processes involving O 2- 2p and Fe 3+ 3d levels. The transition at 464 nm, which has a longer lifetime, was assigned to the relaxation of the excited states produced after electron excitations from O 2- 2p to Zn 2+ 4s levels. Thus, under illumination with wavelengths shorter than 464 nm, electron-hole pairs are produced in ZFO by two apparently independent mechanisms. Furthermore, the charge carriers generated by the O 2- 2p to Zn 2+ 4s electronic transition at 464 nm were found to have a higher incident photon-to-current efficiency than the ones generated by the O 2- 2p to Fe 3+ 3d electronic transition. As the degree of inversion of ZFO increases, the probability of a transition involving the Zn 2+ 4s levels increases and the probability of a transition involving the Fe 3+ 3d levels decreases. This effect contributes to the increase in the photoelectrochemical efficiency observed for the ZFO photoanodes having a larger cation distribution.

AB - Physicochemical properties of spinel ZnFe 2O 4 (ZFO) are known to be strongly affected by the distribution of the cations within the oxygen lattice. In this work, the correlation between the degree of inversion, the electronic transitions, the work function, and the photoelectrochemical activity of ZFO was investigated. By room-temperature photoluminescence measurements, three electronic transitions at approximately 625, 547, and 464 nm (1.98, 2.27, and 2.67 eV, respectively) were observed for the samples with different cation distributions. The transitions at 625 and 547 nm were assigned to near-band-edge electron-hole recombination processes involving O 2- 2p and Fe 3+ 3d levels. The transition at 464 nm, which has a longer lifetime, was assigned to the relaxation of the excited states produced after electron excitations from O 2- 2p to Zn 2+ 4s levels. Thus, under illumination with wavelengths shorter than 464 nm, electron-hole pairs are produced in ZFO by two apparently independent mechanisms. Furthermore, the charge carriers generated by the O 2- 2p to Zn 2+ 4s electronic transition at 464 nm were found to have a higher incident photon-to-current efficiency than the ones generated by the O 2- 2p to Fe 3+ 3d electronic transition. As the degree of inversion of ZFO increases, the probability of a transition involving the Zn 2+ 4s levels increases and the probability of a transition involving the Fe 3+ 3d levels decreases. This effect contributes to the increase in the photoelectrochemical efficiency observed for the ZFO photoanodes having a larger cation distribution.

KW - Cation distribution

KW - Degree of inversion

KW - Photoelectrochemical activity

KW - ZnFe O

UR - http://www.scopus.com/inward/record.url?scp=85067075341&partnerID=8YFLogxK

U2 - 10.3390/catal9050434

DO - 10.3390/catal9050434

M3 - Article

VL - 9

JO - CATALYSTS

JF - CATALYSTS

SN - 2073-4344

IS - 5

M1 - 434

ER -