Hydrothermal synthesis and characterization of transition metal (Mn/Fe/Cu) co-doped cerium oxide-based nano-additives for potential use in the reduction of exhaust emission from spark ignition engines

The goal of this work was to synthesize new cerium oxide-based nano-additives to minimise emissions from spark ignition (SI) engines fueled with gasoline blends, such as carbon monoxide (CO), unburned hydrocarbons (HC) and oxides of nitrogen (NOx). To investigate the effect of transition metal dopants on their respective catalytic oxidation activity, nano-sized CeO2 catalysts co-doped with Mn, Fe, Cu and Ag ions were successfully produced by a simple hydrothermal technique. The synthesis of nano-catalysts with cubic fluorite geometry was confirmed by XRD data. The addition of transition metal ions to the CeO2 lattice increased the concentration of structural defects like oxygen vacancies and Ce3+ ions, which are advantageous for the catalytic oxidation reaction, as also supported by XAFS and RAMAN analysis. Further, nano-gasoline fuel emission parameters are measured and compared to straight gasoline fuel. The results demonstrated that harmful exhaust pollutants such as CO, HC and NOx were significantly reduced. The high surface area, better redox characteristics and presence of additional oxygen vacancy sites or Ce3+ ions have been linked to the improved catalytic performance of the synthesized catalyst.