One-electron reducibility of isolated copper oxide on alumina for selective NO–CO reaction

• Published in: Applied catalysis. B, Environmental Vol. 64; no. 3-4; pp. 282 - 289
• Main Authors: Amano, Fumiaki, Suzuki, Sosuke, Yamamoto, Takashi, Tanaka, Tsunehiro
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 02-05-2006; Elsevier
• Subjects: Al2O3; Catalysis; Chemistry; Exact sciences and technology; General and physical chemistry; NO reduction with CO; Oxygen; Selective catalytic reduction; Theory of reactions, general kinetics. Catalysis. Nomenclature, chemical documentation, computer chemistry; XAFS; Cu; Oxygen; Selective catalytic reduction; Al2O3; XAFS; NO reduction with CO; Aluminium oxide; Catalytic reaction; Reducibility; Transition element compounds; Chemical reduction; Heterogeneous catalysis; Nitric oxide; Carbon monoxide; Copper oxide; Alumina; Electrons; Environmental protection
• ISSN: 0926-3373; 1873-3883
• DOI: 10.1016/j.apcatb.2005.12.011

The H2-TPR (temperature-programmed reduction) study was performed for supported copper oxide catalysts with low loading (0.5wt% as copper). Among the various kinds of support materials (γ-Al2O3, TiO2, ZrO2, SiO2, ZSM-5), alumina-supported copper oxide indicated a one-electron reduction behavior of Cu2+ into Cu+ ions in the presence of H2. The reduction of the isolated Cu2+ species in a tetragonally distorted octahedral symmetry into the low coordinated Cu+ ions was identified by means of X-ray absorption spectroscopy (XANES and EXAFS). The isolated Cu+ ions hosted by γ-Al2O3 surface were prevented from further reduction into metallic Cu0 state under reducing condition with H2 at 773K. Less dispersed supported copper oxide species were easily reduced to Cu0 metal particles with H2 at 573K regardless of the kinds of support materials. It is suggested that the one-electron redox behavior of the isolated copper oxide species over γ-Al2O3 promotes the catalytic reduction of NO with CO in the presence of oxygen on the basis of redox-type mechanism between Cu2+ and Cu+ in atomically dispersed state.