I found many students want to calculate the Ce3+/Ce4+ ratio, but in some cases, they spend a lot of time and cannot do it quickly.

There are many papers on how to calculate the ratio and results can be different , but I think the following method is quite simple and would work:

Details see：

https://www.researchgate.net/publication/342352967_A_shortcut_calculation_method_to_determine_Ce_3_Ce_4_ratio

(1). Firstly, material containing ceria should be characterized with x-ray photoelectron spectroscopy (XPS). For example, the XPS measurements can be performed with a thermo scientific NEXSA system equipped with an Al anode X-ray source and a multi-channel hemispherical analyzer.

(2).Then, XPS spectra of Ce 3d and O 1S should be fitted with suitable parameters as shown in Table 1.

(3).Analysis

The XPS spectra of Ce 3d for ceria are complicated. The three 3d3/2-3d5/2 spin-orbit-split doublets [f 2(β,τ), f 1(δ,η) and f0(ε,θ)] can be associated to Ce4+ with the ground state of Ce 3d94f0, the excited state of Ce 3d94f1VMO-1 and the final state of Ce 3d95p54f0np, respectively. And the doublet peaks [t0(α,σ), t 1(γ,ζ)] at 880.2, 884.5 897.8 and 902.9 eV can be attributed to Ce3+ species. (see ref. V. Matolín, I. Matolínová, L. Sedláček, K. Prince, T. Skála, Nanotechnology 2009, 20, 215706.).

The Ce3+/Ce4+ ratio can be calculated by area integration of α, β, γ, δ and ε peaks by using strictly set fitting parameters, as they collaboratively characterize the Ce 3d5/2 section.

So,

Ce4+ fraction = (β +δ + ε) / ( α + β + γ + δ + ε),

Ce3+ fraction = (α + γ) / ( α + β + γ + δ + ε)

and the

Ce3+/Ce4+ ratio = (α + γ) / (β +δ + ε)

If you got a printed paper of the Ce XPS spectrum, the area of the each peak is not easy to calculate. So you may do manual integral calculation to evaluate the ratio.

Since the peak θ is well pronounced and total peaks area A calculated from 877.5 to 893.7 eV is readily acquired, (ref. to K. I. Maslakov, Y. A. Teterin, A. J. Popel, A. Y. Teterin, K. E. Ivanov, S. N. Kalmykov, V. G. Petrov, P. K. Petrov, I. Farnan, Appl. Surf. Sci. 2018, 448, 154-162.), a shortcut calculation also can be proposed as:

Ce4+ fraction ≈ (1.5θ+3θ)/(A+1.5θ),

Ce3+ fraction ≈ (A-3θ)/(A+1.5θ),

and the

Ce3+/Ce4+ ratio ≈ (A-3θ)/4.5θ.

The rough algorithm can be used in fast evaluation of Ce4+ reduction degree.

O 1s spectrum approximately at 528.5, 530.7 and 532.6 eV can be assigned to O2-, O1-, OChem (chemically adsorbed oxygen on the surface). (Refer to 1) J.-C. Dupin, D. Gonbeau, P. Vinatier, A. Levasseur, Phys. Chem. Chem. Phys. 2000, 2, 1319-1324; 2) L. Q. Wu, Y. C. Li, S. Q. Li, Z. Z. Li, G. D. Tang, W. H. Qi, L. C. Xue, X. S. Ge, L. L. Ding, AIP Adv. 2015, 5, 097210. )

Does anyone have suggestions? Please email me: [email protected]