Identification of Cu(I) and Cu(II) oxides by electron spectroscopic methods: AES, ELS and UPS investigations

doi:10.1016/0368-2048(80)80035-1

Journal of Electron Spectroscopy and Related Phenomena

Volume 19, Issue 1, 1980, Pages 77-90

https://doi.org/10.1016/0368-2048(80)80035-1 Get rights and content

Abstract

The externally prepared black-coloured copper oxide (T⋍ 700 K, P_O₂ ⋍ 100 torr) on a Cu(100) surface is identified by electron spectroscopy as CuO. Compared to the red-coloured Cu(I) oxide (in situ oxidation at T ⩾ 400 K, P_O₂ ⩽ 0.5 torr, ∼ 10⁹ L), the He(I)- excited photoemisson from CuO reveals characteristic shake-up satellites 10–12 eV below E_F and a broadened emission from overlapping oxygen-induced 2p and Cu 3d states. From the AES and ELS results, in correlation with the data from core electron spectroscopy, chemical shifts of Cu 2p, Cu 3s and Cu 3p in CuO to higher binding energy and decreases in binding energy of the oxygen-induced states were deduced. The unoccupied electron states of Cu at 5 and 7.5 eV above E_F — postulated from the ELS results — are preserved in Cu₂O and CuO compounds. Annealing of the Cu(II) oxide at 670 K is accompanied by decomposition into Cu₂O due to the solid-state reaction following the scheme: 2CuO → 1/2 O₂ + Cu₂O.

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Citation Excerpt :
These peak positions are different from those of Cu and Cu2O. Considering the results from Ref. [270] together with UV photoelectron spectra (UPS), the CuOband structures are presented in Fig. 58b. Several authors have also reported on the positions of the photochemically determined CB and VB edges of CuO [271–274].
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Surface composition changes at stainless steel anodes in an electrochemical reactor applied for the electrochemical treatment of cuprocyanide-containing wastewaters operating under different hydrodynamic conditions were investigated. Under highly alkaline conditions in situ generation of a surface film on the anode with catalytic properties towards cyanide electrolysis was observed. X-ray photoelectron spectroscopy (XPS) results demonstrated that only copper oxi-hydroxide compounds constitute the surface film developed on the stainless steel anodes, as no traces of N- and C-containing compounds were observed. The collected XPS spectra revealed relevant details concerning the oxidation states of copper in the film, and the products Cu₂O, CuO and Cu(OH)₂ were identified on the surface of the anodes. However, the quantitative proportions of the individual products differ and depend on the type of mixing employed during reactor operation.
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We report the use of near-edge X-ray absorption fine structure (NEXAFS) to unambiguously characterize the oxidation state of copper in copper oxides. The method is based on the analysis of the oxygen K-edge and copper L-edge features of Cu₂O and CuO powder materials. To further demonstrate its utility, NEXAFS was also used to follow spectroscopically the oxidation of a Cu(100) single crystal surface by NO₂, and the thermal decomposition of the resulting oxides. In agreement with previous studies [J.A. Rodriguez, J. Hrbek, J. Vac. Sci. Technol. 12 (1994) 2140], our NEXAFS results indicate that NO₂ dissociates on the metal surface, generating NO and atomic oxygen which subsequently reacts with the Cu(100) surface to produce Cu₂O (300 K) or a mixture of Cu₂O and CuO (250 K). Upon heating, the thermodynamically unstable CuO transforms into Cu₂O.
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¹: Present address: Max-Planck-Institut für Eisenforschung GmbH, Max-Planck-Strasse 1, D-4000 Düsseldorf, W. Germany.

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Identification of Cu(I) and Cu(II) oxides by electron spectroscopic methods: AES, ELS and UPS investigations

Abstract

Surt Sci.

Surf. Sci.

Surf. Sci.

J. Electron Spectrosc. Relat. Phenom.

J. Electron Spectrosc. Relat. Phenom.

Surf. Sci.

Surf. Sci.

J. Phys. Chem. Solids

Surf. Sci.

Phys. Rev. B

Proc. R. Soc. London