Boreskov Institute of Catalysis of the Siberian Branch of Russian ...

PP-II-4DEACTIVATION OF Rh(410) SURFACE IN THE COURSE OF COOXIDATION UNDER HIGH OXYGEN PRESSURESA.V. Matveev, V.V. Kaichev, I.P. Prosvirin, A.A. Sametova, M.A. Vorobev 1 ,V.V. Gorodetskii, B.E. Nieuwenhuys 2Boreskov Institute of Catalysis SB RAS, pr. Ak. Lavrentieva, 5, Novosibirsk, 630090, Russiae-mail: matveev@catalysis.ru1 Novosibirsk State University, pr. Ak. Koptyuga, 2, Novosibirsk, 630090, Russia2 Leiden Institute of Chemistry, Leiden, 2504, the NetherlandsCO oxidation is one of the most studied reactions, due to its ecological importance incleaning of the tailing gases. But till now there is no common agreement in the understandingof the active state of catalysts in the course of reaction: is it oxide or clean metal surface? Thiswork was devoted to studying the influence of oxide formation under reaction conditions onactivity of Rh(410) single-crystal in CO oxidation.A complex of physical methods was used in the study: temperature-desorptionspectroscopy (TDS), temperature-programmed reaction (TPR), low-energy electrondiffraction (LEED), X-ray photoelectron spectroscopy (XPS). The experiments wereperformed in UHV chamber with residual gas pressure in the chamber ~ 1×10 –10 mbar. Highpressureexperiments were performed in pretreatment chamber 2 . The Rh(410) (4(100)×(110))surface was choose as a model of a real defective catalyst surface.It was shown by XPS and ex-situTDS&LEED studies that at high ratios0.5R=р(O 2 )/p(CO)>10 and temperatureR:range 300-800 K, the oxide layer forms1cooling branchon the surface of the Rh(410). Accordingto TPR data, the activity of surfacecovered by oxide is lower, than the clean51050surface (i.e. at R550 K. Atlower temperatures the dependencelg(W) on lg(p O2 ) has volcanic shape and200 400 600 800 1000 1200finally, at T ≈ 350 K n O2 ≈ 1.2.According to literature [1] at high θ СО(i.e. low temperature) n≈ 1÷2, but at lowTemperature (K)Fig. 1. The decreasing of the catalytic activity of theRh(410) surface in CO oxidation with increasing ofratio R=р(O 2 )/p(CO).θ СO and existence of atomic oxygen on the surface (i.e. at T>500 K) the reaction order must beIntensity CO 2(arb. un.)279