Shape-controlled Nano-sized Metal Oxides for Catalytic Abatement of Diesel Soot Emissions

The development of shape-controlled nano-sized metal oxides has drawn enormous research interest due to their size- and shape-dependent unique properties. In this study, nanosized CeO2 cubes and Co3O4-decorated CeO2 nanocubes were developed using practicable synthesis methods. A range of advanced analytical techniques, namely, HRTEM, STEM-EELS, XPS, XRD, Raman, BET surface area, and H2-TPR have been used to investigate the physicochemical properties of the nanomaterials. The application of these nanoshaped materials was tested for catalytic abatement of diesel soot emissions, a huge environmental problem all over the world. The HRTEM studies confirmed the decoration of Co3O4 nanoparticles (~8 ± 2 nm) on (100)-faceted CeO2 nanocubes (~20 ± 2 nm). This decoration led to a significant improvement in the redox properties of CeO2 nanocubes as evidenced by XPS and H2-TPR studies. It was found that the Co3O4-decorated CeO2 nanocubes show an outstanding catalytic performance compared to pure CeO2 nanocubes in the purification of diesel soot emissions: the achieved temperatures for 50% soot conversion are ~607 and 723 K, for Co3O4/CeO2 and CeO2 nanomaterials, respectively. The remarkable performance of Co3O4-decorated CeO2 nanocubes is attributed to the enhanced redox properties of cerium oxide and the preferential exposure of shape-dependent CeO2 (100) and Co3O4 (110) active facets.