Synergy between Fe and Promoter Ions Supported on Nanoceria Influences NO_x Reduction Catalysis

Fe and Fe–O dispersed on nanoscale CeO supports are considered promising catalysts for oxidation and reduction catalysis and regarded as one of the better alternatives to precious metal catalysts for NO reduction. To understand the role of Fe ions, promoters, and factors that control the NO_x reduction, we probed the local environments of Fe, Ce, and O using a range of spectroscopies. The order of Na promotion (sequential vs simultaneous) resulted in a significant difference in the catalytic activity by changing the local electronic structure around the Fe ions in reaction the conditions. The Ce M_4,5- and O K-edge X-ray spectroscopy results suggest stabilization of the 4f, e_g orbitals, where Fe and promotor ions are affecting the t_2g orbitals. Optimizing this bonding environment around the Fe active species with a promoter ion enables tuning of the NO reduction activity.