Iron oxides with a reverse spinel structure: impact of active sites on molecule adsorption. Issue 10 (30th August 2019)

• Record Type: Journal Article
• Authors: Jian, Wei; Jia, Ran; Wang, Jian; Zhang, Hong-Xing; Bai, Fu-Quan
• Is Part Of: Inorganic chemistry frontiers. Volume 6:Issue 10(2019)
• Page Start: 2810
• Page End: 2816
• Publication Date: 2019-08-30
• Subjects: Chemistry, Inorganic -- Periodicals; 546.05
• DOI: 10.1039/c9qi00790c
• Languages: English
• ISSNs: 2052-1553

Abstract

Abstract : Fe3 O4 and γ-Fe2 O3 with the same crystal structure reflect different catalytically active sites leading to different catalyst properties. Abstract : Fe3 O4 and γ-Fe2 O3 with a reverse spinel structure have been widely applied as environmentally benign catalysts. Clarifying the catalytically active sites (CASs) of Fe3 O4 and γ-Fe2 O3 plays a crucial role in improving the efficiency of related reactions. However, the surface adsorption and electronic properties at the atomic level of Fe3 O4 and γ-Fe2 O3 are not fully understood. Here, the molecules adsorbed at the tetrahedral (Fetet ) and octahedral (Feoct ) sites on the Fe3 O4 and γ-Fe2 O3 surfaces are considered by density functional theory with the Hubbard- U method. According to the results of adsorption energy, as a whole, γ-Fe2 O3 is more favorable to adsorb oxygen than Fe3 O4 . Furthermore, the electronic structure and periodic natural bond orbital results clearly reveal that O2 at the octahedral sites of Fe3 O4 and at the tetrahedral sites of γ-Fe2 O3 obtains more charge; namely, the Feoct ions of Fe3 O4 and the Fetet ions of γ-Fe2 O3 act as CASs in the activation of O2 . To ensure the accuracy of the results, the adsorption of CO, H2 O, NH3 and NO is calculated comparatively. The results suggest that Fe3 O4 and γ-Fe2 O3 with the same crystal structure reflect different CASs. This work provides a foundation for understanding the redox and catalytic application of iron oxides; more importantly, the different CASs of Fe3 O4 and γ-Fe2 O3 have not been proposed before.