Comparative study of surface modification on redox property of CeO2 and CeO2 based catalysts / Nur Masyitah Az-Zahra Rosman and Nur Fadzeelah Abu Kassim

Cerium oxide (CeO2) is used in a variety industrial applications process and CeO2 based materials have been used in environmental applications due to its potential to reverse or block environmental damage and reduce the emission of toxic pollutant. The significant influences on CeO2 performance depend on the surface properties of materials which can develop the transition between Ce3+ and Ce4+ ions. The controllable regulation on their surface features such as surface defects is an efficient approach to intensify their catalytic activity. The objective of this review study is to identify the best technique used to regulate the surface defects of CeO2 catalysts based on its redox properties by referring several articles such as pressure regulations and annealing temperatures, chemical doping, and post-treatment. The results of measured oxygen storage capacity (OSC) from TPR and Ce3+ concentration from XPS analysis were analyzed. The existence of oxygen vacancies and their transportation in the crystal cell of CeO2 is influential as it led to the generation of Ce3+ species. Thirteen articles were used as the main references to identify the measurement of OSC and Ce3+ concentration produced from those techniques. Based on the previous studies, the pressure regulations and annealing temperatures have increased the OSC measurement by 67.24% and 60.25%. For chemical doping technique, it showed that Ce3+ surface fraction had increased by 25.8%. The post-treatment technique had also increased the Ce3+ surface fraction by 13% in the presence of reducing/oxidizing agents. In conclusion, the comparison on relative measured OSC or Ce3+ surface fraction with catalytic efficiency for each technique has been done and it shows that the performance of the catalytic activity obtained the highest efficiency with 96.5% by using post-treatment compared to other techniques. Hence, the best technique to modify the surface of CeO2 is post-treatment in the presence of reducing/oxidizing agents.