Optimization of Ce_(0.6)Zr_(0.4-x)Al_(1.3)xO_2 solid solution based on oxygen storage capacity

摘要

High oxygen storage capacity (OSC) materials are very much demanded for catalytic applications and ceria is one of the promising OSC materials widely used in three-way catalysts. The objective of the present work is to overcome the inherent limitations of ceria by doping Al~(3+) and Zr~(4+) into its lattice and optimize the concentration of dopant based on its OSC. A solid solution of Ce_(0.6)Zr_(0.4-x)Al_(1.3x)O_2 (CZA) (0.0 ≤ x ≤ 0.4) was synthesized by sol-gel technique and the concentration of Zr and Al was optimized based on the maximum OSC of CZA. In all the samples, the lattice defects on the structure were observed and confirmed by HRTEM and Raman spectroscopy. The crystal size of CZA samples was observed to be varied from 2.7 to 7.5 nm. The crystallite growth of CZA was observed to be less compared to that of ceria-zirconia solid solution after the ageing treatment. The OSC of the sample was calculated by the cyclic heating and cooling process in the temperature range of 30-800 °C using Thermogravimetric analysis and the same was observed to be varied from 0.108 to 0.230 lmol g~(-1) of CeO_2. The coefficient of thermal expansion, which was qualitatively used to confirm the OSC, was measured using the thermomechanical analyser and it was observed to be high in Ce_(0.6)Zr_(0.2)Al_(0.26)O_2 compared to that of Ce_(0.6)Zr_(0.4)O_2 and the same was found to be significant after 600 °C. It is concluded that Ce_(0.6)Zr_(0.2)Al_(0.26)O_2 has the highest OSC among all the samples, which could be explored for the potential catalytic applications.