Pt-Doped NiFe2O4 Spinel as a Highly Efficient Catalyst for H2 Selective Catalytic Reduction of NO at Room Temperature

H-2 selective catalytic reduction (H-2-SCR) has been proposed as a promising technology for controlling NOx emission because hydrogen is clean and does not emit greenhouse gases. We demonstrate that Pt doped into a nickel ferrite spinel structure can afford a high catalytic activity of H-2-SCR A superior NO conversion of 96% can be achieved by employing a novel NiFe1.95Pt0.05O4 spinel-type catalyst at 60 degrees C. This novel catalyst is different from traditional H-2-SCR catalysts, which focus on the role of metallic Pt species and neglect the effect of oxidized Pt states in the reduction of NO. The obtained Raman and XPS spectra indicate that Pt in the spinel lattice has different valence states with Pt2+ occupying the tetrahedral sites and Pt4+ residing in the octahedral ones. These oxidation states of Pt enhance the back-donation process, and the lack of filling electrons of the 5d band causes Pt to more readily hybridize with the 5 sigma orbital of the NO molecule, especially for octahedral Pt4+, which enhances the NO chemisorption on the Pt sites. We also performed DFT calculations to confirm the enhancement of adsorption of NO onto Pt sites when doped into the Ni-Fe spinel structure. The prepared Pt/Ni-Fe catalysts indicate that increasing the dispersity of Pt on the surfaces of the individual Ni-Fe spinel-type catalysts can efficiently promote the H-2-SCR activity. Our demonstration provides new insight into designing advanced catalysts for H-2-SCR.