Mixed H₂O/H₂ plasma-induced redox reactions of thin uranium oxide films under UHV conditions

Abstract

X-Ray Photoelectron Spectroscopy (XPS) has been used to study the effect of mixed H2O/H2 gas plasma on the surface of UO2, U2O5 and UO3 thin films at 400 °C. The...

Green carbon–carbon homocoupling of terminal alkynes by a silica supported Cu(ii)-hydrazone coordination compound

“…7c), the peak at lower BE (524.66 eV) is due to the Cu–O bond and the peaks at 531.31, 532.88, 534.04 and 535.35 eV can be related to the O–H, OC, (O–C/O–N) and O–Si bonds, respectively. 35 In the XPS spectrum of N 1s (Fig. 7d), there is a broad peak which can be divided into six peaks.…”

Exploring the Change in Redox Reactivity of UO2 Induced by Exposure to Oxidants in HCO3– Solution

“…As can be seen, the measured U 4f 7/2 and U 4f 5/2 in the reference samples are close to 380.0 and 391.0 eV, respectively, which is in line with previous results. ,, Both peaks shift to higher binding energy after exposure to O 2 , H 2 O 2 , or γ-radiation, indicating that the surface was oxidized. There are four methods that can indicate oxidation states of uranium from XPS spectra: (1) deconvolution of the U 4f 7/2 peak; (2) distance between the U 4f 5/2 peak and its corresponding satellite peaks; (3) peak center and FWHM of the O 1s peak; and (4) peak area ratio between O 2p 3/2 and U 5f. − The present work will utilize all four methods to investigate the oxidation state of uranium. Note that only method 1 was used for quantitative analysis.…”

“…Since the shape of U 4f 5/2 peaks is affected by the satellite peaks generated from U 4f 7/2 peaks, deconvolution was only performed for U 4f 7/2 peaks. Each U 4f 7/2 peak was assumed to contain three components including U­(IV), U­(V), and U­(VI). ,, The peak positions in the U 4f 7/2 peak deconvolution process were chosen on the basis of the peak positions of pure U­(IV), U­(V), and U­(VI) materials. The deconvolution principle for mixed valence oxidized UO 2 samples is according to the guidance in ref , in which a fixed Gaussian–Lorentzian characteristic, one variable but identical FWHM for each component peak, and a floating peak center is suggested.…”

“…It is interesting to note that in experiments where pure U­(V) phases (U 2 O 5 ) have been produced by reducing U­(VI) (UO 3 ), both the U­(V) and the U­(VI) phases have layered structures and reduction of U­(V) to U­(IV) involves a structural rearrangement. This structural rearrangement is also expressed in terms of kinetic inertia of the process . This deserves to be studied in more detail.…”

“…For the surface analysis, specimens exposed to either O 2 , H 2 O 2 , or γ-radiation in aqueous solutions containing 10 mM HCO 3 – were used. The XPS and UPS results were analyzed using the following methods: (1) deconvolution of U 4f 7/2 peak; (2) energy difference between the U 4f 5/2 peak and its corresponding satellite peaks; (3) peak center and FWHM of the O 1s peak; (4) peak area ratio between O 2p 3/2 and U 5f. − The observed impact of exposure on the reactivity of UO 2 is discussed in view of the XPS and UPS results.…”