In situ XPS data for the uranyl-modified oxides under visible light

The silica, alumina, ceria, and titania supports were modified with uranyl ions (5 wt%) and investigated using X-ray photoelectron spectroscopy. The data show the U4f photoelectron spectra and charge state of uranium for uranyl ions deposited on different supports. The additional in situ XPS experiments with simultaneous irradiation of the sample using a 450 nm light-emitting diode were performed, and the XPS spectra, revealing a partial reduction of uranium under visible irradiation, are presented. The data show the effect of support material on the chemical states of uranium and oxygen on the surface of uranyl-modified oxides under visible light.


a b s t r a c t
The silica, alumina, ceria, and titania supports were modified with uranyl ions (5 wt%) and investigated using X-ray photoelectron spectroscopy. The data show the U4f photoelectron spectra and charge state of uranium for uranyl ions deposited on different supports. The additional in situ XPS experiments with simultaneous irradiation of the sample using a 450 nm light-emitting diode were performed, and the XPS spectra, revealing a partial reduction of uranium under visible irradiation, are presented. The data show the effect of support material on the chemical states of uranium and oxygen on the surface of uranyl-modified oxides under visible light.

Subject area
Surface chemistry More specific subject area Photochemistry Type of data Figure,   In situ XPS technique has great promise for the investigation of photochemical processes on the surface of different materials.

Data
In this study, in situ XPS experiments when the sample in a spectrometer chamber was simultaneously irradiated using 450 nm LED were performed to understand the behavior of uranyl species under the visible light on the surface of different oxides. Figs. 1-4 show the photoelectron U4f and O1s spectral regions for the 5 wt% uranyl-loaded samples based on SiO 2 (5US), Al 2 O 3 (5UA), CeO 2 (5UC), and TiO 2 (5UT), respectively, before and after irradiation using 450 nm LED. According to literature data [1][2][3][4][5][6], different positions of the U4f 7/2 peaks (Figs. 1-4a) can be attributed for different charge states of uranium. The relationship between the binding energy and corresponding charge state of uranium is shown in Table 1.
The peaks observed in the O1s spectral region (Figs. 1-4b) can be attributed to the lattice oxygen, surface oxygen, oxygen from water and OH groups. The relationship between the position of the O1s peaks and the chemical state of oxygen was suggested on the basis of previously published papers [7][8][9].
The results for each sample are shown in Table 2.
The collected photoelectron spectra were used for the calculation of the ratio between the different chemical states of uranium and oxygen. The data for each sample before and after long-term 450 nm LED irradiation are shown in Table 3. In the table, lattice oxygen is referred to as O lat , and the combination of the other oxygen forms is marked as O rest .

Sample preparation
The silica, alumina, ceria, and titania supports were modified with uranyl ions via the impregnation method using UO 2 (NO 3 ) 2 aqueous solution [11]. Typically, 0.5 g of a support was suspended in 10 mL of deionized water, and 1 mL of 0.063 M aqueous solution of UO 2 (NO 3 ) 2 was added to the suspension. The theoretically calculated content of UO 2 (NO 3 ) 2 in the samples was 5 wt%. After vigorous stirring for 30 min, the suspension was evaporated. The precipitate was dried at 100°C in air followed by the final grinding using an agate mortar and pestle.

X-ray photoelectron spectroscopy
A SPECS (Germany) spectrometer equipped with a hemispherical PHOIBOS-150-MCD-9 analyzer and FOCUS-500 (AlKα radiation, hλ ¼ 1486.74 eV, 200 W radiation power) monochromator was employed for in situ XPS experiments. In addition to a typical packaging, the presence of a special window in the analyzer chamber allowed for simultaneous irradiation of the investigated sample with visible light during the spectra collecting (Fig. 5). The sample preparation for the XPS analysis was performed under room irradiation from luminescent lamps. The position of the oxide-forming element for support was used as an internal standard for the calibration of photoelectron spectra. The analysis of each sample was performed as follows: (1) Spectra collecting for the initial sample (i.e., without 450 nm LED irradiation); (2) Spectra collecting for the sample 450 nm LED irradiated for a certain period; (3) Spectra collecting after long-term irradiation (i.e., 1-2 h) and turning LED off.
The ratio between different charge states of a particular element was calculated using the areas of corresponding spectral lines or curve-fitted peaks, respectively.

Acknowledgments
This work was conducted within the framework of the budget project #АААА-А17-117041710087-3 for Boreskov Institute of Catalysis.

Transparency document. Supplementary material
Transparency document associated with this article can be found in the online version at https:// doi.org/10.1016/j.dib.2018.06.121.