TAILIEUCHUNG - Characteristics and reducibility of nanosized La1-xCexCoO3 perovskites synthesized by reactive grinding
The thermal stability of cobalt ions in such solids has been studied under reducing conditions. H2-TPR results indicate that the reduction of Co3+ to Co0 occurs in a multiple-step. The partial replacement of La3+ by Ce4+ has promoting effects on the reducibility of cobalt ions. A decreased reduction temperature of cobalt ions in the presence of Ce4+ leads to an increased dispersion of the reduced phase for perovskite precursor. | Journal of Chemistry, Vol. 47 (5), P. 552 - 557, 2009 Characteristics and reducibility of nanosized La1-xCexCoO3 perovskites synthesized by reactive grinding Received 7 June 2008 1 NGUYEN TIEN THAO , NGO THI THUAN1, SERGE KALIAGUINE2 1 Faculty of Chemistry, College of Sciences, Vietnam National University, Hanoi 2 Department of Chemical Engineering, Laval University, Canada. G1K 7P4. Abstract Two (La,Ce)CoO3 perovskite-type oxides prepared by reactive grinding have been characterized by means of X-ray diffraction, N2 adsorption/desorption isotherms, SEM, H2-TPR. Both samples show a nanocrystalline phase and rather high surface area. The thermal stability of cobalt ions in such solids has been studied under reducing conditions. H2-TPR results indicate that the reduction of Co3+ to Co0 occurs in a multiple-step. The partial replacement of La3+ by Ce4+ has promoting effects on the reducibility of cobalt ions. A decreased reduction temperature of cobalt ions in the presence of Ce4+ leads to an increased dispersion of the reduced phase for perovskite precursor. Keywords: perovskite; reduction; cobalt; La-Ce-Co; dispersion; metal. I - Introduction Perovskite-type oxides with the general formula ABO3 have been much paid special attention for the last three decades due to their potential applications in catalysis and pollutant elimination [1]. For example, some perovskites such as LaCoO3, LaMnO3, LaCrO3 have been used in environmental catalysis reactions including CO oxidation, methane combustion, NOx decomposition, and exhaust treatment [12]. However, these applications are mainly based on the electronic configuration of the B3+ cations. In recent years, there has been an interest in using mixed-oxide type perovskites Ln(Co,Fe, Ni, Cu)O3 as prominent precursors for preparation of a “metal on oxide” solid [35]. Because of the complexity of perovskite system which often contains mixed valence ions and variable stoichiometry, a transition metal 552 with
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