Noguera C, Goniakowski J. Mixing properties of Al
2O
3(0001)-supported
M2O
3and
MM'O
3monolayers (
M,
M' = Ti, V, Cr, Fe).
JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2021;
34:034002. [PMID:
34598168 DOI:
10.1088/1361-648x/ac2c3d]
[Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/30/2021] [Accepted: 10/01/2021] [Indexed: 06/13/2023]
Abstract
Considering the importance of sub-monolayer transition metal oxides supported on another oxide in many industrial processes, with the help of a DFT +Uapproach, we provide information on the structural and electronic properties of pureM2O3and mixedMM'O3oxide monolayers (M,M' = Ti, V, Cr, Fe) supported on anα-Al2O3(0001) support. With their structure in the prolongation of the alumina corundum lattice, the monolayers have non-equivalent surface and interface cations, which leads to two different cation configurations in the mixed oxides. In all cases, the interfacial charge transfer is weak, but strong cation-cation electron redistributions may take place as in TiVO3, TiFeO3, VFeO3, and TiCrO3in which actual redox processes lead to cation oxidation states different from the expected +3 value. We show that the tendency to mixing relies on the interplay between two very different driving forces. Cation-cation redox reactions, in most cases, strongly stabilise mixed configurations, but preference for a given cation position in the monolayer, because of surface energy reasons, may strengthen, weaken or even block the mixing tendency. By comparison with results obtained in bulk ilmenite, in free-standing monolayers and in MLs deposited on transition metal substrates, we evidence the flexibility of their electronic structure as a function of size, dimensionality and nature of support, as a lever to tune their properties for specific applications.
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