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

The exposed crystal facets are crucial to heterogeneous catalysis . Herein, the facet controlled Ce 1−x La x O δ (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 , H 2 -TPR, and so forth. With the increasing content of La 3+ , part of CeO 2 crystals transformed from nanocubes to nanorods , inducing distinct effects on the catalytic activity . When the concentration of La 3+ was lower than 10 %, the exposed facet in the catalyst was (200). After La 3+ were further introduced, the facet degraded to (111). La 3+ 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 La 3+ ions would inhibit CO 2 desorption due to the generation of La 2 O 2 CO 3 , a strong alkali as a result of phase separation. Among all the catalysts, Ce 0.95 La 0.05 O δ showed the best catalytic performances for soot combustion, with T 50 of 375 °C.