Journal
JOURNAL OF PHYSICS AND CHEMISTRY OF SOLIDS
Volume 148, Issue -, Pages -Publisher
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.jpcs.2020.109699
Keywords
Hematite; Cr dopant; Mossbauer spectroscopy; Morin transition; Optical band gap
Funding
- Croatian Science Foundation [IP-2016-06-8254]
- Ministry of Science and Education of the Republic of Croatia (bilateral Croatian-Serbian scientific project)
- Ministry of Education, Science and Technological Development of the Republic of Serbia (bilateral Croatian-Serbian scientific project)
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The study investigated the impact of different levels of Cr doping on the properties of hematite nanorods, confirming the effect of Cr3+-for-Fe3+ substitution in the crystal structure and the enhancement of visible light photocatalytic activity induced by Cr doping.
Pure and Cr-doped hematite (alpha-(Fe1-xCrx)(2)O-3, x = 0, 0.026, 0.039, 0.085 or 0.135) nanorods were prepared by a simple co-precipitation and calcination method. Influence of different levels of Cr doping on the change of properties of long and thin pure hematite nanorods was investigated. Cr3+-for-Fe3+ substitution in the crystal structure of hematite was proved by measuring a gradual contraction of the unit cell and a gradual decrease of the hyperfine magnetic field by increasing the Cr molar fraction. Cr doping induced an increase in the width and thickness of hematite nanorods, as well as a decrease in the overall surface area. Low temperature Fe-57 MOssbauer spectroscopy showed that the Morin transition in hematite was suppressed by Cr doping to temperatures below 80 K. Magnetic measurements confirmed the suppression of the Morin transition in Cr-doped hematite down to 5 K. Infrared spectra of Cr-doped hematite samples showed shifts of IR bands by Cr3+-forFe(3+) substitution. Optical properties of alpha-Fe2O3 nanorods changed significantly by Cr doping - the absorption edge was shifted to higher wavelengths, accompanied by a greater absorption in the visible range and narrowed direct and indirect optical band gaps. The improved visible light photocatalytic activity of hematite nanorods in the heterogeneous photo-Fenton process by moderate Cr doping was measured, which can be attributed to the modifications in electronic structure and optical properties.
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