Enhanced soot oxidation by lattice oxygen via La3+-doped CeO2

The catalytic behaviours of CeO2 and a series of La3+-doped CeO2 catalysts (La3+ loading between 5 and 50 wt%) have been studied for soot oxidation by O2. XRD and Raman spectroscopy characterisation indicated that solid solutions are formed in the studied Ce/La ratio, in which La3+ cations replace Ce4+ cations in the CeO2 lattice. Thermogravimetric analysis showed that La3+ significantly improves CeO2 catalytic activity for soot oxidation with O2. The best catalytic activity was found with 5 wt% La3+-doped CeO2 catalyst (CeO2-5La), in both loose and tight contact conditions. This improvement seems to be related to the increase in BET surface area and the change in the catalyst redox properties of CeO2 brought about by doping with La3+. La3+ decreases the onset temperature of Ce4+ to Ce3+ reduction by H2 from 580 °C (CeO2) to 325 °C (CeO2-5La) and increases the amount of Ce4+ that can be reduced by H2 (maximum amount for CeO2-5La catalyst).