Design of 3-dimensionally self-assembled CeO2 hierarchical nanosphere as high efficiency catalysts for toluene oxidation

3-Dimensionally (3D) hierarchical CeO2 nanospheres with different compositions were synthesized via simple methods without the use of templates. The samples are self-assembled by nanoparticle, nanorod and small nanosphere (named as PS, RS and HS) respectively. As-synthesized materials were characterized by HRTEM, SEM, XRD, H-2-TPR, Raman spectroscopy, and BET surface area analyzer. Characterization of these materials showed differences in the specific surface areas, pore sizes, surface compositions, oxygen vacancies and redox properties. Among all the three samples, HS exhibited the best toluene catalytic activity which could achieve a 90% toluene conversion (T-90) at 205 degrees C. HS sample shows an almost 6 times TOFov of RS at 180 degrees C and a lower Ea of 62.936 kJ mol(-1). The high catalytic performance of HS could be attribute to its relatively large specific surface area and the hierarchical porous structures which could provide more contents of surface oxygen vacancies. In addition, HS sample also shows an excellent stability in long-term test and under vapor condition.