Valence States in CeVO₄ and Ce_0.5Bi_0.5VO₄ Probed by Density Functional Theory Calculations and X-ray Photoemission Spectroscopy

Abstract

Ce is one of the few lanthanide elements to exhibit well-defined (III) and (IV) oxidation states in solid-state environments, and there is therefore ambiguity as to whether CeVO 4 should be formulated as Ce(III)V(V)O 4 or Ce(IV)V(IV)O 4 . To address this question, CeVO 4 and Ce 0.5 Bi 0.5 VO 4 have been studied by density functional theory calculations and X-ray photoemission spectroscopy. A peak above the main O 2p valence band in photoemission is attributed to localized Ce 4f states, in agreement with the calculations which show occupation of Ce 4f states. The Ce 3d core level spectrum is diagnostic of Ce(III) with no sign of a peak associated with 4f 0 final states that are characteristic of Ce(IV) compounds. The experimental and theoretical results thus confirm that both compounds contain Ce(III) and V(V), rather than Ce(IV) and V(IV). In agreement with experiment, the calculations also show that the tetragonal zircon phase adopted by CeVO 4 is more stable for Ce 0.5 Bi 0.5 VO 4 than the monoclinic clinobisvanite phase adopted by BiVO 4 , so that the formation of the stereochemically active Bi(III) lone pairs is suppressed by Ce doping.

Cerium vanadate/carbon nanotube hybrid composite nanostructures as a high-performance anode material for lithium-ion batteries

“…The appeared peaks at 883 and 886.6 eV are corresponding to the binding energy of Ce 3d 5/2 , whereas the peaks centered at 901.6 and 904.7 eV are assigned to Ce 3d 3/2 [19]. Also, the observed peak at 917.4 eV is corresponding to the spin-orbit coupling of Ce 3d 3/2 , indicating the existence CeO 2 phase [31]. Therefore, the existed bonding energy of Ce 3d 5/2, 3/2 implies the existence of Ce 4+ and Ce 3+ valence states in the prepared sample.…”

“…From the core level V 2p spectrum (Fig. 2d), the obtained peaks approximately at 516.4 and 523.74 eV are assigned to the spin-orbit coupling of 2p 3/2 and 2p 1/2 , which indicates the existence of V 3+ valence state, while those about at 517.72 and 525.32 eV are assigned to the V 2p 3/2 and V 2p 1/2 of V 5+ [19,31]. The core-level spectrum of O 1s (Fig.…”

Electronic Structure of Lanthanide-Doped Bismuth Vanadates: A Systematic Study by X-ray Photoelectron and Optical Spectroscopies

“…A single sharp peak is observed above the main valence band of Bi 0.5 La 0.5 VO 4 . As discussed previously, this must arise from the ionization of a single 4f electron characteristic of the 2 F 5/2 states of Ce­(III) to give a 1 S 0 final state . The observation of this peak is thus a diagnostic of Ce­(III) + V­(V) valence states: a much weaker 3d peak would be found for a Ce­(IV) + V­(IV) valence state configuration, owing to the lower ionization cross-section for V 3d as compared to Ce 4f.…”

“…Here, we present a study of all 14 accessible quaternary compounds of general formula Bi 0.5 Ln 0.5 VO 4 (Ln = lanthanide), owing to the highly radioactive nature of promethium, this lanthanide could not be included. As mentioned above, the parent lanthanide vanadates themselves adopt a tetragonal zircon structure based on vanadate tetrahedra and almost-regular lanthanide LnO 8 polyhedra, with two Ln–O bond lengths that typically differ by about 0.1 Å. − As a preliminary to preparation of a complete series of quaternary compounds, we explored the phases formed by high-temperature reaction between Bi 2 O 3 , Dy 2 O 3 and V 2 O 5 to give Bi 1– x Dy x VO 4 solid solutions with x values between 0 and 1. Although mixed phase material was obtained for x ≤ 0.3, only the tetragonal phase was formed when x ≥ 0.4.…”

Influence of Cu doping on the visible-light-induced photocatalytic activity of InVO4

“…The aim of doping impurities into InVO 4 is to modify the physicochemical properties of the material, which depend upon the type of impurity doping (shallow or deep) and the nature of the valence of the impurity (inert lattice mismatching, donor or acceptor). [22][23][24] Copper is a transition metal ion and is widely used as a dopant in metal oxide semiconductors because it can extend optical absorption toward longer wavelengths, provide a large surface area for the adsorption of chemical species, and enable efficient separation of photogenerated charge carriers. 25 Therefore, identifying appropriate dopants and dopant concentrations is crucial to increase the overall performance of a photocatalyst.…”