Exposed crystal facet tuning of CeO2 for boosting catalytic soot combustion: The effect of La dopant

Abstract

The exposed crystal facets are crucial to heterogeneous catalysis. Herein, the facet controlled Ce1−xLaxOδ (0 ≤ x ≤ 0.30) nanocomposites have been constructed elaborately via a hydrothermal route and used for soot abatement. The catalysts were characterized by XRD, TEM, Raman, FT-IR, XPS, H2-TPR, and so forth. With the increasing content of La3+, part of CeO2 crystals transformed from nanocubes to nanorods, inducing distinct effects on the catalytic activity. When the concentration of La3+ was lower than 10 %, the exposed facet in the catalyst was (200). After La3+ were further introduced, the facet degraded to (111). La3+ at low concentration would enhance activity by facilitating lattice oxygen delivery and inducing abundant surface oxygen species, especially O-, which were vital to surface sensitive soot oxidation. Nevertheless, excessive La3+ ions would inhibit CO2 desorption due to the generation of La2O2CO3, a strong alkali as a result of phase separation. Among all the catalysts, Ce0.95La0.05Oδ showed the best catalytic performances for soot combustion, with T50 of 375 °C.