title: Platinum Inhibits Low-Temperature Dry Lean Methane Combustion through Palladium Reduction in Pd-Pt/Al2O3: An In Situ X-ray Absorption Study.
abstract: Palladium-platinum bimetallic catalysts supported on alumina with palladium/platinum molar ratios ranging from 0.25 to 4 are studied in dry lean methane combustion in the temperature range of 200 to 500 °C. Platinum addition decreases the catalyst activity, which cannot be explained by the decrease in dispersion or the structure sensitivity of the reaction. In situ X-ray absorption near-edge structure and extended X-ray absorption fine structure spectroscopy measurements have been conducted for monometallic Pd, Pt, and 2:1 Pd-Pt catalysts. Monometallic palladium is fully oxidized in the full temperature range, whereas platinum addition promotes palladium reduction, even in a reactive oxidizing environment. The Pd/PdO weight ratio in bimetallic Pd-Pt 2:1 catalysts decreases from 98/2 to 10/90 in the 200-500 °C temperature range under the reaction conditions. Thus, platinum promotes the formation of the reduced palladium phase with a significantly lower activity than that of oxidized palladium. The study sheds light on the effect of platinum on the state of the active palladium surface under low-temperature dry lean methane combustion conditions, which is important for methane-emission control devices.
authors: Department of Chemical and Materials Engineering, University of Alberta, 9211-116 St., Edmonton, Alberta, T6G 1H9, Canada.
authors: Hanieh
authors: H
authors: Nassiri
authors: Department of Chemistry, University of Saskatchewan, 110 Science Place, Saskatoon, Saskatchewan, S7N 5C9, Canada.|Canadian Light Source Inc., 44 Innovation Boulevard, Saskatoon, Saskatchewan, S7N 2V3, Canada.
authors: Kee-Eun
authors: KE
authors: Lee
authors: Canadian Light Source Inc., 44 Innovation Boulevard, Saskatoon, Saskatchewan, S7N 2V3, Canada.
authors: Yongfeng
authors: Y
authors: Hu
authors: Department of Chemical and Materials Engineering, University of Alberta, 9211-116 St., Edmonton, Alberta, T6G 1H9, Canada.
authors: Robert E
authors: RE
authors: Hayes
authors: Department of Chemistry, University of Saskatchewan, 110 Science Place, Saskatoon, Saskatchewan, S7N 5C9, Canada.
authors: Robert W J
authors: RW
authors: Scott
authors: Department of Chemical and Materials Engineering, University of Alberta, 9211-116 St., Edmonton, Alberta, T6G 1H9, Canada.
authors: Natalia
authors: N
authors: Semagina
keywords: X-ray absorption spectroscopy; heterogeneous catalysis; nanoparticles; oxidation; reaction mechanism