XPS Study of Metal-Support Interaction in Ru/MgO Catalyst for Low-Temperature Ammonia Synthesis
Yu. V. LARICHEV1, 2, B. L. MOROZ2, I. P. PROSVIRIN2, V. A. LIKHOLOBOV1, 2 and V. I. BUKHTIYAROV2
1Novosibirsk State University,
Ul. Pirogova 2, Novosibirsk 630090 (Russia), E-mail: prsv@catalysis.nsk.su
2 G. K. Boreskov Institute of Catalysis, Siberian Branch of the Russian Academy of Sciences,
Pr. Akademika Lavrentyeva 5, Novosibirsk 630090 (Russia), E-mail: moroz@catalysis.nsk.su
Abstract
The catalytic system Ru/MgO has been characterized by TEM and XPS in the Ru 3d, Cl 2p and O1s regions. It was shown, that the treatment of the sample with H2 at 450 °Ñ leads to reduction of supported Ru (III, IV) chloride complexes to Ru metal crystallites of 2–5 nm in size (the surface atomic ratio Ru : Cl of reduced sample is 6.2). The shift of Ru 3d peak (279.5 eV) to lower bond energy (BE) found for Ru/MgO sample as compared with bulk Ru metal (280.2 eV) is proved to be due to the differential charging effect. The value of this effect was estimated by a comparison of the valence band spectrum of supported Ru particles with that of bulk Ru. Taking the differential charging into account, the "true" value BE of Ru 3d5/2 (280.5 eV) was determined. The shift of Ru 3d peak towards the higher BE values may indicate the electron-withdrawing effect of MgO surface to supported Ru particles.
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