Adsorption of V on a hematite (0 0 0 1) surface and its oxidation: Submonolayer coverage

• Published in: Surface science Vol. 601; no. 14; pp. 3082 - 3098
• Main Authors: Jin, Jianjian, Ma, Xiaoyan, Kim, C.-Y., Ellis, D.E., Bedzyk, M.J.
• Format: Journal Article
• Language: English
• Published: Lausanne Elsevier B.V 15.07.2007; Amsterdam Elsevier Science; New York, NY
• Subjects: ADSORPTION; ADSORPTION HEAT; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Cross-disciplinary physics: materials science; rheology; DENSITY FUNCTIONAL METHOD; Density functional theory; Exact sciences and technology; HEMATITE; INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; OXIDATION; Physics; SORPTIVE PROPERTIES; Surface oxidation; VANADIUM; Vanadium adsorption; Hematite; Density functional theory; Vanadium adsorption; Surface oxidation; Transition elements; Vanadium; Density functional method; Oxidation; Coverage rate
• ISSN: 0039-6028; 1879-2758
• DOI: 10.1016/j.susc.2007.05.028

The adsorption of submonolayer V on an idealized model hematite (0 0 0 1) surface and subsequent oxidation under atomic O adsorption are studied by density functional theory. The preferred adsorption sites, adsorption energy and configuration changes due to V and O adsorption are investigated. It is found that in most cases V forms threefold bonds with surface O atoms, inducing a large geometry change at the hematite surface and near surface region and a bond stretch between surface Fe and O. The adsorption energy is mainly decided by interplay between adsorbed metal-surface oxygen bonding and adsorbed metal – subsurface metal interaction. The relative energy of subsequent O adsorption and geometry depends on the reformed V/hematite structure. Electronic properties such as projected densities of states and chemical state change upon V adsorption are studied through both periodic slab and embedded cluster localized orbital calculations; both strong vanadium–oxygen and vanadium–iron interactions are found. While V generally donates electrons to a hematite surface, causing nearby Fe to be partially reduced, the Fe and V oxidization state depends very much on the coverage and detailed adsorption configuration. When the V/hematite system is exposed to atomic O, V is further oxidized and surface/near surface Fe is re-oxidized. Our theoretical results are compared with X-ray surface standing wave and X-ray photoelectron spectroscopic measurements. The influence of d-electron correlation on the predicted structures is briefly discussed, making use of the DFT + U scheme.