Loofa sponage derived multi-tubular CuO/CeO2-ZrO2 with hierarchical porous structure for effective soot catalytic oxidation

In this work, a series of multi-tubular CuO/CeO2-ZrO2 catalysts (denoted as xHc@CZs) with hierarchical porous structure were obtained by using loofah sponage as biotemplate. The morphology and surface chemical environments were analyzed by SEM, TG-DSC, N-2-adsorption-desorption, XRD, H-2-TPR, and XPS measurements. The removal of biotemplate can lead to brittle multi-channels and many fractured sheets that were favorable to the enlarged soot/catalyst contact degree and enhanced catalytic performance (T-50 = 396-411 degrees C). With increased copper ions entered the cubic lattice of ceria-zirconia, the separation of Ce-rich (Ce0.75Zr0.25O2) and Zr-rich (Ce0.16Zr0.84O2) tetragonal phases was accelerated, which was negative for the catalytic performance. The redox equilibrium Cu2+ + Ce3+ <-> Cu+ Ce4+ existed on the surface and lattice of the catalysts, which lead to the highest surface oxygen species (O-surf, 44.0%) for 1Hc@CZs. The higher degree of phase separation, as well as cracked multi-tubular structure could be the main reasons for the relative low catalytic activities with higher contents of copper ions. The sample 1Hc@CZs represented good reusability (T-50 maintained at 435 degrees C under five recycles), which displayed excellent prospects in the practical applications.