Synthesis of Ceria Nanomaterials to Enhance Catalytic Activity of CO Oxidation

Abstract

This thesis represents a comparative study of a series of ceria nanomaterials towards CO oxidation. Ceria particles were synthesized using microwave-assisted hydrothermal and one-step solvothermal methods, and ceria nanofibers were synthesized using the electrospinning technique. 6 transition metals have been selected namely, copper (Cu), nickel (Ni), cobalt (Co), manganese (Mn), iron (Fe), and lanthanum (La) as dopants for ceria nanofibers. The formation and respective physicochemical properties of the materials were confirmed by employing XRD analysis, BET surface area measurements, SEM, TEM, Raman, and XPS techniques. All the doped ceria nanofibers exhibited smaller crystallite size and higher amounts of oxygen vacancies than that of pure ceria. CO oxidation was performed in the presence of oxygen under atmospheric pressure and 300-750K temperature range in a fixed bed reactor. The physicochemical properties of the ceria materials were comparatively analyzed to correlate the influence of dopants with their CO oxidation activity. The role of ‘lattice oxygen’ and surface areas was considered, assuming that Mars Van Krevelen (MVK) mechanism plays a key role in CO oxidation activity. For the pure ceria materials with different morphologies, they had similar CO oxidation activity when they have similar BET surface area values. Copper doping significantly increased the CO oxidation activity and the already existing oxygen vacancy was not the determining factor for the CO oxidation.