A review on cerium oxide–based catalysts for the removal of contaminants

Cerium oxide–based catalytic materials are of interest due to their high catalytic performance. These oxides are widely used in the oxidation of contaminants emitted from automotive exhaust. The variable oxidation state of cerium between + 3 and + 4 is responsible for its high catalytic activity. The exhaust emitted from diesel engines contains various contaminants such as CO, NOx, CO2, carbon soot, and unburned hydrocarbons, which are the major cause of air pollution. The various health problems such as skin infections, asthma, eye irritation, cancer, and cardiovascular problems are evolved due to air pollution. To overcome the problems arising from diesel engines, diesel particulate filters (DPFs) are being used in diesel engines. To prevent the filter from deterioration at high temperature, the filters are coated with cerium oxide–based nanomaterials which stabilize it at high temperature. In this review article, the study of materials doped in ceria for the removal of contaminants has been done. The reactivity of catalysts on the basis of their particle size, surface area, and processes of synthesis is also discussed. The effect of doping and increasing amount of doping in ceria leads to the change in reactivity of material, creating oxygen vacancies and surface oxygen and changing its oxidation state at low temperature, which provide its high catalytic activity towards the removal of automotive exhaust. The various parameters, by which catalytic activity of the catalyst is affected, have been discussed here.