Infrared Studies on Bimetallic Copper/Nickel Catalysts Supported on Zirconia and Ceria/Zirconia.

Astrid Kitla,Olga V Safonova,Karin Föttinger

doi:10.1007/s10562-013-1001-y

Abstract

Infrared spectroscopy has been employed for a detailed characterization of ZrO2 and CeO2/ZrO2 supported nickel and copper/nickel catalysts to be utilized for methane decomposition. Adsorption of CO at 303 K was performed in order to determine the surface composition and accessible adsorption sites. Alloy formation occurred during reduction, as indicated by a red-shift of the vibrational band of CO on Ni: by 27 cm−1 on nickel-rich CuNi alloy, by 34 cm−1 on 1:1 Cu:Ni and by 36 cm−1 on copper-rich CuNi alloy. CuNi alloy formation was confirmed by X-ray absorption spectroscopy during reduction revealing a considerably lower reduction temperature of NiO in the bimetallic catalyst compared to the monometallic one. However, hydrogen chemisorption indicated that after reduction at 673 K copper was enriched at the surface of the all bimetallic catalysts, in agreement with IR spectra of adsorbed CO. In situ IR studies of methane decomposition at 773 K demonstrated that the addition of Cu to Ni strongly reduced coking occurring preferentially on nickel, while maintaining methane activation. Modification of the zirconia by ceria did not have much effect on the adsorption and reaction properties. Ceria-zirconia and zirconia supported samples exhibited very similar properties and surface chemistry. The main difference was an additional IR band of CO adsorbed on metallic copper pointing to an interaction of part of the Cu with the ceria.Graphical

Highlights

The global need of energy, rising oil prices and environmental requirements to reduce CO2 emissions increase the interest in alternative energy generation, such as fuel cells as clean and efficient means of energy production
CuNi alloy formation was confirmed by X-ray absorption spectroscopy during reduction revealing a considerably lower reduction temperature of NiO in the bimetallic catalyst compared to the monometallic one
The main difference was an additional IR band of CO adsorbed on metallic copper pointing to an interaction of part of the Cu with the ceria

Summary

Introduction

The global need of energy, rising oil prices and environmental requirements to reduce CO2 emissions increase the interest in alternative energy generation, such as fuel cells as clean and efficient means of energy production. Fuel cells that run directly on hydrogen are considered clean because the exhaust is only water, but this ignores the fact that the vast majority of H2 is generated by reforming of hydrocarbons, such as methane, [2] producing CO or CO2 by-product. The production of hydrogen from hydrocarbons by internal reforming in solid oxide fuel cells (SOFCs) represents a good alternative. Catalysts are used for the production of H2 from hydrocarbons (preferentially from sustainable sources), and catalysts are used directly in solid oxide fuel cells for e.g. methane reforming or oxygen activation. H2 can be produced by methane steam reforming [3,4,5], (1), dry reforming [4, 6,7,8,9,10,11,12,13], (2) or partial oxidation [14, 15], (3) of methane

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