Effect of Zr4+ doping on the stabilization of ZnCo-mixed oxide spinel system and its catalytic activity towards N2O decomposition

Abstract

Cobalt-zinc hydroxycarbonate precursor with nominal Co/Zn atomic ratio of 2 and 0.05-0.15 mol% ZrO2-doped precursors have been synthesized from their metal nitrate and sodium carbonate by coprecipitation route. ZnCo2O4 spinel oxide was formed during the precipitation process as complemented by FTIR. Decomposition of the Co/Zn precursor at 350 °C resulted in the formation of ZnCo2O4 as evidenced by XRD technique. Zr4+-doped samples stabilized the ZnCo2O4 phase and suppressed the formation of ZnO phase at 550 and 750 °C. The highest surface areas (SBET) were attained for the samples doped with 0.15 mol% ZrO2. Activation energy of sintering derived from XRD and SBET data was directly proportional to the dopant concentration. ESR results revealed that the addition of increased amounts of Zr4+ enhances the formation of Co2+ ions. The activity of the 350 and 750 °C calcined catalysts was tested for N2O direct decomposition. The observed activities were related to the presence of Co2+-Co3+ ion pairs which were enhanced by the addition of Zr4+ ions. © 2009 Elsevier B.V. All rights reserved.