Removal of NOx species from automotive emissions continues to be a challenge, particularly using replacements for Pt-group metals. Here, we demonstrate the synthesis of FeOx domains on CeO2 from the precursor Fe ethylenediaminetetraacetate (NaFeEDTA) and its utility in the reduction of NO with H2 as a model reaction for tailpipe emissions. Diffuse-reflectance UV-visible and X-ray absorption near-edge spectroscopies indicate the formation of small, non-crystalline FeOx domains. Using the EDTA precursor, TPR and in situ XANES show that up to 45% of the FeOx centers were capable of undergoing redox cycles in H2 up to 550°C, whereas only 23% of FeOx centers derived from Fe(NO3)3 were redox active. Similarly, at comparable Fe surface densities, the FeEDTA-derived catalysts were more active than the nitrate-derived materials in the reduction of NO to N2 (85-95% selectivity) with H2 at 450°C. The presence of both the bulky organic ligand and the alkali is essential for the observed enhancements in fraction redox active and to achieve high NO reduction rates. Rates over all materials were fit to a single correlation against the number of redox-active FeOx centers, suggesting that these are the catalytic active sites. The new materials describe here may offer new avenues for emissions control without Pt-group metals or substituted zeolites.
ASJC Scopus subject areas
- Environmental Science(all)
- Process Chemistry and Technology